Alicia Growney, M.D., Steven D. Bines, M.D.
A
Surgical Infection
1 A patient is seen at the hospital after a trip to Texas with a 2-week history of fever, chills, cough, and right-sided pleuritic chest pain. The patient has otherwise been healthy and does not take any medication. He does not have any allergies. Physical examination showed an icteric young man with a temperature of 102° F (38.9° C) and tender hepatomegaly. Breath sounds are decreased in the right lower lobe. A computerized axial tomographic (CT) scan of the chest and abdomen shows a mass in the right lobe of the liver compatible with an abscess. Which of the following empirical antibiotic therapies should be started?
A Ampicillin, gentamicin, and clindamycin
B Levofloxacin and gentamicin
C Piperacillin/tazobactam, clindamycin, and amikacin
D Cefoxitin, gentamicin, and metronidazole
E Imipenem and clindamycin
Ref.: 1, 2
Comments
This patient has a liver abscess, the two possible causes being bacterial or amebic in origin. The symptoms of both may be similar, and clinical differentiation between them is not usually possible. The diagnosis can be made by requesting serologic studies for ameba or by obtaining an aspirate of the fluid collection. Before identifying the etiologic agent, the empirical antimicrobial treatment must cover polymicrobial bacterial infection (including aerobic gram-negative rods and anaerobes), as well as Entamoeba histolytica.
Gentamicin and levofloxacin provide good coverage for gram-negative organisms. Cefoxitin covers both gram-positive and gram-negative organisms. Clindamycin and metronidazole are effective against anaerobes. In addition, metronidazole is the antimicrobial of choice for E. histolytica. Imipenem and piperacillin/tazobactam cover both gram-negative organisms and anaerobes. Because of the emergence of multidrug resistant bacteria, the best initial combination for empirical broad antibiotic coverage is a second-generation cephalosporin and an aminoglycoside with metronidazole.
Answer
D
2 A patient with recurrent duodenal ulcer is referred for surgical consultation. He has been having recurrent abdominal pain for the last 2 years. Fifteen months ago, upper endoscopy showed a duodenal ulcer. The patient was treated with ranitidine and his condition improved, but the symptoms recurred. Upper endoscopy confirmed a recurrent ulcer, and the result of a Campylobacter-like organism (CLO) test was positive. The patient was treated with a combination of two antibiotics and a proton pump inhibitor for 2 weeks. Which of the following tests best assesses eradication of Helicobacter pylori after completion of treatment?
A Urea breath test
B CLO test
C Biopsy and culture
D Serum antibody (by enzyme-linked immunosorbent assay [ELISA])
E Stool antibody test
Ref.: 3
Comments
Surgery for the treatment of peptic ulcers is indicated only in the following circumstances: intractable hemorrhage, perforation, and obstruction. The patient does not have any of these conditions. Furthermore Helicobacter pylori, the most important pathophysiologic factor in the development of duodenal ulcer, was never adequately treated. Treatment options for H. pylori are numerous, but they must always include an H2 blocker or a proton pump inhibitor plus at least two antibiotics. The antibiotics most commonly used are amoxicillin, clarithromycin, and metronidazole. Bismuth-containing regimens have also been used. Depending on the combination used, the length of treatment varies from 2 to 4 weeks.
Methods of diagnosing H. pylori can be divided into two categories: invasive and noninvasive. Biopsy and the campylobacter pylori test require endoscopy, but all the other tests do not. Like the CLO test, the urea breath test takes advantage of the ability of H. pylori to split urea. However, the urea breath test only requires the patient to “blow,” whereas the CLO test is conducted on a piece of tissue. The serologic test for H. pylori antibody is useful but of limited value in determining the success of therapy. There is no stool “antibody” test for H. pylori, but a stool antigen test is available and is as sensitive as the urea breath test.
Since there is no need for repeated endoscopy in this patient, the clinician must consider the relative merits of the noninvasive methods. Because antibody test results may remain positive after treatment, the best choice is the urea breath test, which determines the presence of live H. pylori.
Answer
A
3 A woman is recovering well after surgery for appendicitis complicated by secondary peritonitis. A second-generation cephalosporin (cephamycin) was administered perioperatively. On her third day of hospitalization, urine culture reveals Candida spp. and Enterococcus faecalis. The patient has remained afebrile since surgery, and her vital signs are stable. Physical examination reveals an intubated young woman who is awake and calm. Her abdomen is soft and nontender, and she has a urinary catheter in place. Her white blood cell count is 5.4 thou/cu mm with a normal differential count. Urinalysis revealed many white blood cells, many epithelial cells, and many bacteria. Which of the following is the best treatment for this woman?
A Resume cephamycin.
B Start fluconazole and vancomycin.
C Start amphotericin B and linezolid.
D Start amphotericin B bladder washes and vancomycin.
E There is no need for antimicrobials.
Ref.: 1
Comments
A positive culture result does not always indicate infection or the need for treatment. Urinary catheters predispose to urinary tract infections. However, infections generally produce symptoms such as fever, abdominal pain, dysuria, frequency, and leukocytosis. This patient has contaminated urine (many epithelial cells) with colonization by several microorganisms. There is no need to treat her. It may be advisable to change or remove her catheter and repeat a urinalysis and urine culture. When more than one organism is seen in the urine, it is most likely a contaminated sample.
Answer
E
4 A 10-year-old boy who recently emigrated from Mexico has had a 2-day illness characterized by fever, odynophagia, dysphagia, and drooling at the mouth. Physical examination reveals a child in a toxic condition with a temperature of 102° F (38.9° C), tachycardia, and tachypnea. There is mild tenderness in the submandibular area and few palpable lymph nodes. The suspected diagnosis is epiglottitis, which is confirmed with a CT scan of the neck. Blood culture results are positive. What kind of organism will probably be seen on Gram stain?
A Gram-positive cocci in pairs and chains
B Gram-positive cocci in clusters
C Slender gram-negative rods
D Gram-negative coccobacilli
E Spirochetes
Ref.: 1
Comments
The patient has acute epiglottitis, most likely attributable to Haemophilus influenzae type B, which is recovered from the blood in up to 100% of cases. Classically, the patient is a 2- to 4-year-old boy with a short history of fever, irritability, dysphonia, and dysphagia, which can occur at any time of the year. However, the widespread use of H. influenzae type B vaccine in developed countries has led to a marked decline in invasive disease with this organism. The disease is still common in developing countries, however. Haemophilus species are gram-negative coccobacilli. Treatment includes early intubation, with plans for cricothyroidotomy or tracheotomy if intubation fails, and antibiotic such as ceftriaxone or ampicillin/sulbactam.
Answer
D
5 A diabetic patient has recently been discharged from the hospital after intracranial bleeding. He is readmitted for aspiration pneumonia. His condition deteriorates rapidly, with hypotension and multiorgan dysfunction. Which of the following treatments is contraindicated?
A Volume resuscitation
B Antibiotics
C Activated protein C
D Intensive insulin therapy for hyperglycemia
E Low-dose hydrocortisone
Ref.: 4
Comments
Severe sepsis is characterized by multiorgan dysfunction with or without shock and is due to a generalized inflammatory and procoagulant response to infection. Efforts to improve the outcome with anticytokine therapy along with antibiotics and supportive care have until recently not been associated with improved survival. Recently, a randomized, double-blind, placebo-controlled multicenter trial evaluating recombinant activated protein C has demonstrated a survival benefit in patients with severe sepsis. However, activated protein C treatment was associated with an increased risk for bleeding and is contraindicated in patients with recent hemorrhagic stroke. Fluid resuscitation and antibiotics are mainstays in the treatment of sepsis. Intensive insulin therapy that maintains serum glucose levels at 80 to 110 mg/dL reduces morbidity and mortality in critically ill patients. The mechanism is unknown, but it is possible that correcting hyperglycemia may improve neutrophil function. The use of corticosteroids for sepsis remains controversial. High doses of corticosteroids may in fact worsen outcomes by increasing the frequency of secondary infections. However, low doses of corticosteroids may be beneficial in septic patients, who may have “relative” adrenal insufficiency despite elevated levels of circulating cortisol. Although the issue is controversial, the use of low-dose hydrocortisone is not contraindicated in this patient.
Answer
C
6 A patient in whom angioedema develops after the administration of penicillin is scheduled for a craniotomy to ablate a seizure focus. Which of the following choices is appropriate for antibiotic prophylaxis?
A Cefazolin from the time of surgery and then for 7 days
B No antibiotic prophylaxis
C Vancomycin at the time of induction and then for 3 to 5 days
D Vancomycin at the time of induction
E Vancomycin and gentamicin at the time of induction
Ref.: 5, 6
Comments
The degree of wound contamination (clean versus contaminated procedure) combined with host factors (e.g., diabetes, advanced age, obesity, immunodeficiency, and nutritional status) and procedure-related factors (e.g., presence of foreign material and the degree of trauma to host tissues) determines the overall risk for the development of a surgical site infection (SSI). Despite state-of-the-art aseptic technique, bacterial contamination of the surgical wound is inevitable. Microorganisms that colonize the skin, such as Staphylococcus aureus, coagulase-negative staphylococci, and streptococci, are the most common wound pathogens, particularly during clean procedures. SSIs associated with contaminated procedures are frequently polymicrobial and are due to the normal flora of the entered viscus (i.e., coliforms and anaerobic bacteria associated with colonic procedures). Prophylactic antibiotics are clearly indicated for most clean-contaminated and contaminated procedures and effectively decrease the rate of SSI. Antibiotic prophylaxis for clean surgery remains controversial in certain cases. However, when bone is incised, as in craniotomy, sternotomy, and placement of orthopedic hardware, antibiotic prophylaxis has proven efficacy in decreasing the incidence of SSIs. Antibiotics selected for clean procedures must have excellent activity against skin microorganisms. Cefazolin is the usual choice. However, as in this case, severe penicillin allergy prevents the use of other β-lactams, including cephalosporins and the carbapenems. Vancomycin is the usual alternative. In addition, clindamycin and trimethoprim/sulfamethoxazole may also be effective prophylactic agents for neurosurgical procedures. The timing of antibiotic administration is critical, and for best results they should be given within 30 minutes of the surgical incision. Redosing during a prolonged procedure is recommended to maintain serum concentrations. The duration of antibiotic prophylaxis following surgery remains a source of disagreement, although administration of antibiotics beyond 24 hours is rarely indicated.
Answer
D
7 Endocarditis prophylaxis is recommended for which of the following patients?
A A patient with mitral valve prolapse but without murmur who is undergoing lithotripsy for renal calculi
B A patient with a history of rheumatic fever and normal cardiac valves who is undergoing prostatic biopsy
C A patient with a prosthetic aortic valve who is undergoing pulmonary resection
D A patient with severe hypertrophic cardiomyopathy who is undergoing endoscopic retrograde cholangiography for biliary obstruction
E A patient previously treated for streptococcal endocarditis who is undergoing colonoscopy
Ref.: 7
Comments
Antibiotic prophylaxis for endocarditis is recommended for patients with certain cardiac conditions who are undergoing any dental procedure that involves the gingival tissues or periapical region of a tooth and for any procedure involving perforation of the oral mucosa. In addition, patients undergoing procedures on the respiratory tract or those with skin or soft tissue infections should also receive prophylaxis. The cardiac conditions associated with the highest risk for adverse outcomes from infective endocarditis for which prophylaxis is indicated before the previously listed procedures include prosthetic heart valves, history of infective endocarditis, congenital heart disease (CHD) limited to unrepaired cyanotic CHD, repaired CHD with prosthetic material or devices during the first 6 months after the procedure, repaired CHD with residual defects at the site or adjacent to the site of a prosthesis, and cardiac transplantation recipients with cardiac valvulopathy. Prophylaxis against viridans group streptococci with a penicillin, cephalosporin, or clindamycin is recommended. Routine prophylaxis in patients undergoing gastrointestinal or genitourinary procedures is no longer recommended.
Answer
C
8 A patient is infected with human immunodeficiency virus (HIV). His last CD4+ T-lymphocyte count was 50 cells/mm3, and his viral load was 100,000 copies/mL. He comes to the hospital with the sudden onset of right hemiparesis. He has been afebrile. A CT scan and magnetic resonance imaging (MRI) of the brain show multiple ring-enhancing lesions in the left cerebral hemisphere. The Toxoplasma IgG antibody test result is positive. He has received pyrimethamine and sulfadiazine for 12 days. Neurologically, the patient is stable. Which of the following is the next best step?
A Repeat MRI of the brain.
B Continue the same antibiotic therapy for an additional 10 days and reassess.
C Switch treatment to pyrimethamine with the addition of clindamycin and reassess whether the patient improves clinically in 10 to 14 days.
D Add corticosteroids to the treatment regimen.
E Perform a positron emission tomographic (PET) or single-photon emission computed tomographic (SPECT) scan.
Ref.: 8
Comments
Up to 90% of human immunodeficiency virus-infected patients with advanced disease (<100 CD4+ cells/mm3), multiple ring-enhancing lesions, and a positive Toxoplasma IgG antibody test result have cerebral toxoplasmosis. Empirical treatment with pyrimethamine, sulfadiazine, and folinic acid is recommended. Most patients with central nervous system (CNS) toxoplasmosis respond rapidly to this therapy, with nearly 90% of patients demonstrating neurologic improvement at 2 weeks. Radiographic improvement occurs at a slower pace, with approximately 50% improvement on repeated MRI of the brain occurring within 3 weeks of initiating treatment. For patients who do not improve by 2 weeks, a brain biopsy is indicated. Although lymphoma is the most likely alternative diagnosis in patients with acquired immunodeficiency syndrome (AIDS) and CNS lesions, up to 25% of brain biopsy specimens reveal toxoplasmosis. Thallium-201 (SPECT) or PET scans may provide useful information in that a “cold” lesion revealed by SPECT or hypometabolic lesions seen on PET scanning are consistent with infection. However, false-positive and false-negative results can occur with these functional imaging studies. Pyrimethamine plus sulfadiazine or clindamycin is considered first-line therapy for toxoplasmosis. The addition of corticosteroids may be useful in the treatment of increased intracranial pressure. However, this antiinflammatory effect may make interpretation of clinical and radiographic responses difficult.
Answer
A
9 Which of the following statements regarding the collection of blood for culture is false?
A The optimal timing for drawing blood for culture is approximately 1 hour before the onset of fever.
B Blood collected via intravascular devices for culture should be paired with blood obtained by peripheral venipuncture.
C At least two sets of blood cultures should be obtained for any patient with suspected bacteremia.
D A minimum of 10 mL of blood should be collected for each set of cultures.
E Blood collected via intravascular devices for culture does not need to be paired with blood obtained by peripheral venipuncture.
Ref.: 9
Comments
Early studies demonstrated that rigors and fever often follow bacteremia by 30 to 90 minutes. Since circulatory phagocytes are generally effective in removing bacteria from the bloodstream, collection of blood for culture should occur as early as possible in the course of a febrile episode. Good data document that two or three sets of blood cultures containing at least 10 mL of blood per set are sufficient for demonstrating most episodes of bacteremia or fungemia. After adequate skin antisepsis, peripheral venipuncture sites are preferred for blood collection for culture. Central venous catheters are frequently used for blood collection but should be paired with a peripheral blood draw to aid in the interpretation of a positive test result. A positive blood culture result obtained from intravenous catheters combined with a negative result from a blood culture obtained from a peripheral site may represent only colonization of the line and not true bacteremia.
Answer
E
10 Which of the following statements regarding anaerobic bacterial infections is true?
A Anaerobic bacteria are common inhabitants of the skin and mucous membranes.
B Bacteroides spp. are the most common isolates in intraabdominal anaerobic infections.
C If appropriate cultures are obtained, anaerobes are found in more than 75% of intraabdominal abscesses.
D Proper treatment of anaerobic infections consists of surgical drainage, débridement of necrotic tissue, and appropriate antibiotic therapy.
E All of the above.
Ref.: 1
Comments
Anaerobic bacteria are normal inhabitants of the skin, mucous membranes, and gastrointestinal tract. In fact, anaerobic bacteria outnumber aerobic organisms by more than 10 : 1 in the oral cavity and by more than 1000 : 1 in the colon. Therefore, it is not surprising that anaerobes are cultured from up to 90% of intraabdominal abscesses. The most common pathogens in this group are Bacteroides spp. Bacteroides fragilis is an important co-pathogen in the pathogenesis of intraabdominal abscesses. As with most serious infections, proper treatment involves appropriate drainage of abscesses and débridement of devitalized tissue when present, as well as appropriate antibiotic therapy. Antibiotics with excellent broad-spectrum anaerobic activity include the carbapenems (imipenem, meropenem, and ertapenem), β-lactam/β-lactamase combinations (ampicillin/sulbactam, ticarcillin/clavulanate, and piperacillin/tazobactam), and metronidazole. Although the second-generation cephalosporins (i.e., cefoxitin and cefotetan) and clindamycin also provide anaerobic coverage, over the past decade an increase in resistance of Bacteroides organisms to these agents has been observed. For example, as many as 30% of B. fragilisisolates are resistant to clindamycin.
Answer
E
11 The use of tigecycline is not indicated for which of the following?
A Methicillin-resistant S. aureus (MRSA) bacteremia
B Community-acquired pneumonia
C Ventilator-associated pneumonia caused by vancomycin-resistant enterococci (VRE)
D Enterobacter cultured from an intraabdominal abscess
E Klebsiella pneumonia soft tissue infection
Ref.: 10
Comments
Tigecycline is part of a new class of antibiotics called the glycylcyclines and has a broad spectrum of activity against gram-positives, gram-negatives, aerobes, and anaerobes, including MRSA. It has no activity against Pseudomonasor Proteus. It is indicated in the treatment of complicated skin and soft tissue infections, complicated intraabdominal infections, and community-acquired pneumonia. Treatment of infections caused by VRE with tigecycline has not been well studied in clinical trials.
Answer
C
12 Which of the following statements regarding tetanus prophylaxis is false?
A A patient has a minor, clean wound. His second tetanus shot was 4 years ago. He requires a dose of tetanus toxoid. Antitetanus immunoglobulin is not required.
B A patient has a minor, clean wound. His third tetanus shot was 5 years ago. He does not require any additional prophylaxis.
C A patient has a dirty wound. He completed three tetanus shots when he was a child but has not had a tetanus booster in 20 years. He is immune and does not require additional toxoid or antitetanus immunoglobulin.
D A patient has a dirty wound. He does not remember when and how many tetanus shots he received in the past. He requires a toxoid dose. Antitetanus immunoglobulin is also required.
E A hematopoietic stem cell transplant (HSCT) recipient should begin reimmunization with tetanus toxoid 12 months after transplantation.
Ref.: 11
Comments
Approximately 100 cases of tetanus occur in the United States annually. Tetanus develops in nonimmune individuals after a penetrating injury is inoculated with spores of Clostridium tetani. With appropriate local anaerobic conditions, these spores germinate and produce a neurotoxin, tetanospasmin, that is responsible for the signs and symptoms of tetanus. The majority of cases of tetanus occur in older adults (>60 years) who have waning immunity. The need for active immunization with tetanus toxoid or passive immunization with human tetanus immunoglobulin (or both) depends on the nature of the wound and the immune status of the patient. Tetanus toxoid and immunoglobulin are indicated for patients with dirty (tetanus-prone) wounds who have received fewer than three doses of tetanus toxoid in the past or whose immunization status is unknown. Dirty wounds include those contaminated with feces, saliva, or soil and wounds related to punctures, gunshots, crush injury, burns, or frostbite. Tetanus toxoid is indicated only for patients with dirty wounds who have received three doses of toxoid more than 10 years ago and have not received a booster within 5 years of the injury. Patients with clean, minor wounds require tetanus toxoid if they have received fewer than three doses of toxoid less than 10 years ago and have not received a booster or the patient’s immune status is unknown. Immunocompromised patients undergoing chemotherapy and HSCT recipients may be at increased risk for tetanus. HSCT recipients should begin reimmunization with tetanus toxoid 12 months after transplantation.
Answer
C
13 Match each agent in the left-hand column with one or more mechanisms of antimicrobial action in the right-hand column.
|
A. Carbapenems |
a. Impairment of bacterial DNA synthesis |
|
B. Aminoglycosides |
b. Inhibition of cell wall synthesis |
|
C. Quinolones |
c. Disruption of ribosomal protein synthesis |
|
D. Cephalosporins |
d. Disruption of cell wall cation homeostasis |
|
E. Vancomycin |
e. Disruption of the cytoplasmic membrane |
Ref.: 12
Comments
All the antimicrobial agents listed are bactericidal agents (i.e., their associated mechanisms of action result in bacterial death). Bacteriostatic agents (e.g., tetracyclines, chloramphenicol, erythromycin, clindamycin, and linezolid) act by preventing bacterial growth but do not result in bacterial death. They work primarily through inhibition of ribosomal protein synthesis. Both carbapenems and cephalosporins are β-lactam antibiotics and hence have a similar mode of activity. Enzymes located within the bacterial cytoplasmic membrane are responsible for peptide cross-linkage. These enzymes are called penicillin-binding proteins (PBPs) and are the site at which β-lactam drugs bind. Such binding interferes with bacterial cell wall synthesis and eventually results in cell lysis. Gram-negative bacteria contain a variable number of various PBPs. Each β-lactam antibiotic has various affinities for the various PBPs. Vancomycin is a glycopeptide that also inhibits bacterial cell wall synthesis and assembly. Vancomycin complexes to cell wall precursors and prevents elongation and cross-linkage, thereby making the cell susceptible to lysis. This antibacterial activity is limited to gram-positive organisms. Aminoglycosides bind irreversibly to the 30S bacterial ribosome and interfere with protein synthesis. For this activity to take place, they must penetrate the cell wall, which occurs optimally under aerobic conditions. Unlike other antibiotics that inhibit protein synthesis, aminoglycosides are bactericidal. This feature is due to their disruptive effect on calcium and magnesium homeostasis within the cell wall. Quinolones inhibit topoisomerase II (DNA gyrase) and topoisomerase IV, which impairs DNA synthesis in bacteria. Appreciation of the mechanism of action of antimicrobials may have a bearing on the selection of alternative therapies when bacterial resistance to the drug of choice develops.
Answer
A-b; B-c,d; C-a; D-b; E-b
14 Which of the following statements concerning cephalosporins is not correct?
A Cefazolin is a reasonable choice for nosocomial urinary tract infection.
B Cefoxitin monotherapy is effective for the treatment of hospital-acquired intraabdominal sepsis.
C Ceftriaxone is effective against Pseudomonas aeruginosa.
D Cefepime is effective against enterococci.
E Cefepime is effective against Enterobacteriaceae and S. aureus.
Ref.: 1
Comments
Cephalosporins are chemically similar to penicillins and have similar mechanisms of action and toxicities. Because cephalosporins are more stable in the presence of bacterial β-lactamases, they have a broader spectrum of antibacterial activity than do penicillins. Cephalosporins are loosely classified into four major groups, or generations, based mainly on the spectrum of antimicrobial activity. In general, first-generation cephalosporins have better coverage for gram-positive organisms, and later generations exhibit improved activity against gram-negative bacteria. Cefazolin is a first-generation cephalosporin that has good coverage of gram-positive cocci. It is also effective against some community-acquired gram-negative bacteria, such as Escherichia coli, but its gram-negative coverage is not adequate, and resistance to it is common. Cefazolin is not appropriate treatment of nosocomial urinary tract infection. Cefoxitin is a second-generation cephalosporin that has demonstrated efficacy in the treatment of intraabdominal, pelvic, and gynecologic infections. These infections are generally due to facultative gram-negative bacilli and anaerobic organisms, especially B. fragilis. However, approximately 15% of B. fragilis isolates may be resistant. Nosocomially acquired organisms, such as Enterobacteriaceae and S. aureus, may be resistant to cefoxitin, thus making cefoxitin monotherapy a poor choice for nosocomial intraabdominal infections. Ceftriaxone is a third-generation cephalosporin that is widely used for community-acquired pneumonia and meningitis. It has excellent coverage against Streptococcus pneumoniae. This cephalosporin does not cover P. aeruginosa, but other third-generation cephalosporins such as ceftazidime do. Cefepime is a fourth-generation cephalosporin that combines the spectra of first- and third-generation cephalosporins. This agent has broad activity against Enterobacteriaceae, P. aeruginosa, and methicillin-susceptible S. aureus. However, cefepime has poor activity against enterococci and B. fragilis.
Answer
D
15 Adverse events associated with the use of quinolones include all of the following except:
A Tendinitis and possible tendon rupture
B Seizures
C Arthropathy in children
D Clostridium difficile colitis
E Narrowing of the QT interval
Ref.: 1
Comments
The quinolones are antibiotics that exert their bactericidal effect by inhibiting topoisomerase II (DNA gyrase) and topoisomerase IV, thereby impairing DNA synthesis. These antibiotics have a broad spectrum of activity that covers many gram-positive cocci, but they are not active against MRSA, and some of them, such as ciprofloxacin, may not adequately treat infections with S. pneumoniae, gram-positive bacilli (anthrax), and many gram-negative species. Gatifloxacin and moxifloxacin have anaerobic activity. Most quinolones also have activity against Mycobacterium tuberculosis and atypical respiratory pathogens such as Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella spp. Adverse effects of quinolones include gastrointestinal intolerance, antibiotic-associated colitis, cutaneous reactions, hepatotoxicity (trovafloxacin was withdrawn from the market for this reason), prolongation of the QT interval (leading to ventricular arrhythmias), and Achilles tendon rupture. Quinolone use is generally avoided in children because animal studies suggest that these drugs cause cartilage erosion. However, children receiving quinolones have rarely experienced joint symptoms, and they appear to be reversible. Results of MRI studies performed to identify subclinical cartilage damage have been negative.
Answer
E
16 Which of the following is not characteristic of aminoglycosides?
A Active against a broad spectrum of gram-negative aerobes and useful for synergy against some gram-positive cocci
B Emergence of resistant bacterial strains
C Narrow margin between therapeutic and toxic blood levels
D Nephrotoxicity, ototoxicity, and neuromuscular paralysis
E Excellent activity in abscesses in which gram-negative organisms are involved
Ref.: 1
Comments
Until the mid-1980s, aminoglycosides were the only reliable empirical treatment of serious gram-negative infections. However, the introduction of third-generation cephalosporins, extended-spectrum penicillins, carbapenems, and quinolones has reduced the frequency of aminoglycoside use. The mechanism of action of aminoglycosides involves irreversible binding to the 30S bacterial ribosome. However, aminoglycosides must first penetrate the cell wall, and since this step is oxygen dependent, it does not occur under anaerobic conditions. For this reason, aminoglycosides have no activity against anaerobic bacteria or facultative bacteria in an anaerobic environment (e.g., an abscess). Aminoglycosides are useful against gram-negative aerobes, including P. aeruginosa, and they are effective as synergistic agents (usually in combination with a β-lactam or vancomycin) against Staphylococcus epidermidis, S. aureus, and enterococci. Resistance to aminoglycosides does occur. Selection of an aminoglycoside should be based on local patterns of resistance. Aminoglycosides are difficult to use clinically because of their low therapeutic-to-toxic level ratio. Monitoring of serum concentrations of aminoglycosides is usually required to achieve safe and therapeutic blood levels. The two major toxic side effects are nephrotoxicity and ototoxicity. The ototoxicity, both auditory and vestibular, is potentially more significant because it is nonreversible and cumulative. The auditory toxicity affects the response to higher frequencies, which makes early detection difficult. The nephrotoxicity is usually a dose-dependent, reversible, acute tubular necrosis that produces nonoliguric renal failure. Paralysis can occur after the administration of aminoglycosides and is due to inhibition of presynaptic release of acetylcholine and postsynaptic blockade of acetylcholine receptors at the neuromuscular junction. Neuromuscular blockade is a rare but potentially lethal event. This risk is increased in patients receiving tubocurarine, succinylcholine, or similar agents and in patients with myasthenia gravis. This effect is reversible with the intravenous administration of calcium carbonate.
Answer
E
17 For which of the following conditions are perioperative antibiotics not indicated?
A Perforated appendix
B Open fracture of the humerus
C Mastectomy
D Traumatic colonic perforation
E Cholecystectomy for acute cholecystitis
Ref.: 13
Comments
Surgical wounds can be classified according to their risk for infection. Clean wounds are defined as nontraumatic in origin. No evidence of inflammation is encountered during surgery, and no breaks in surgical technique occur. There must also not be a breach of the respiratory, alimentary, or genitourinary tract. A good example of a clean surgical wound is a mastectomy wound. Generally, antibiotic prophylaxis is not needed for such procedures. However, in cases of clean-contaminated or contaminated wounds, the use of perioperative antibiotics is indicated. A clean-contaminated wound is a nontraumatic wound in which a minor break in surgical technique occurs or in which the respiratory, gastrointestinal, or genitourinary tract has been entered without significant spillage. Examples include transection of the appendix or cystic duct in the absence of acute inflammation or entrance into the biliary or genitourinary tract without evidence of infected bile or urine. Some debate exists regarding antibiotic prophylaxis for elective open and laparoscopic cholecystectomy. Several studies suggest that wound infection rates are similar in patients regardless of whether they receive prophylactic antibiotics. However, patients considered to be at high risk for infectious complications, including those 60 years or older and those undergoing procedures with evidence of acute inflammation, common bile duct stones, or jaundice, probably benefit from perioperative antibiotics. Patients who have previously undergone biliary tract operations or endoscopic retrograde cholangiopancreatography should also receive perioperative antibiotics. Contaminated wounds include traumatic wounds (e.g., open fractures) and wounds from operations involving a major break in surgical technique, such as gross spillage from the gastrointestinal tract or entrance into the genitourinary or biliary tract in the presence of acute infection. This category also includes dirty wounds, defined as old traumatic wounds with devitalized tissue and those involving existing clinical infections, such as perforated appendix.
Answer
C
18 Which of the following statements regarding clostridial infections is true?
A The presence of clostridial organisms in a surgical or traumatic wound does not warrant immediate antibiotic administration and surgical intervention.
B The oxidation-reduction potential in contaminated tissues is a significant factor in the development of a clostridial infection.
C Despite the potentially fulminant course of clostridial infections, the skin overlying clostridial cellulitis may not be discolored or edematous.
D Clostridial myonecrosis (gas gangrene) should be treated with immediate surgical débridement, antibiotics, and hyperbaric oxygenation.
E A frozen section of soft tissue without polymorphonuclear infiltrates rules out the diagnosis of clostridial myonecrosis.
Ref.: 1
Comments
Clostridial organisms are ubiquitous and are a common contaminant of traumatic wounds. In most wounds, however, the high oxidation-reduction potential of the surrounding healthy tissues prevents colonization and invasion of these tissues. In such cases, the presence of clostridia is clinically insignificant. When colonization with clostridia occurs in the presence of necrotic tissue, proliferation and invasion of other tissue can occur and lead to clostridial cellulitis. This form of clostridial infection is confined to the superficial fascial planes, and although it may spread rapidly, systemic effects may be mild and the skin of normal color. Clostridial myonecrosis occurs when the deeper muscular compartments are invaded, usually by Clostridium perfringens. The inaccessibility of systemic antibiotics to this ischemic, necrotic tissue, coupled with the low oxidation-reduction potential of such wounds, permits rapid dissemination of clostridia through the muscular compartments. Symptoms of clostridial myonecrosis are variable: pain out of proportion to the findings on physical examination; systemic toxicity; a rapidly spreading zone of cellulitis; bronzing of the skin; and a thin, watery, brown discharge. Gram staining reveals large numbers of gram-positive rods and an absence of neutrophils. In the appropriate clinical setting, an innocuous appearance of the postoperative wound does not exclude the possibility of clostridial sepsis. Therapy should include immediate surgical débridement and antibiotic therapy (penicillin G plus clindamycin). Adjuvant hyperbaric oxygen treatment may be helpful, but it has not been evaluated in a randomized, controlled trial.
Answer
E
19 Which of the following statements regarding diabetic foot infections is false?
A Acute diabetic foot infections are often caused by gram-positive organisms.
B Chronic diabetic foot infections are polymicrobial.
C To diagnose an infection in a patient with a chronic wound, a foul odor and redness must be present.
D MRSA infections are associated with a worse outcome.
E Impaired host defenses allow low-virulence colonizers such as coagulase-negative staphylococci and Corynebacterium spp. to become pathogens.
Ref.: 1
Comments
See Question 20.
Answer
C
20 Which of the following regarding the treatment of diabetic foot infections is true?
A Acute diabetic foot infections are caused by monomicrobial gram-negative aerobes.
B The use of antibiotics for an uninfected chronic wound facilitates wound closure and prevents future infection.
C Sharp débridement of necrotic or unhealthy tissue facilitates wound healing and removes a potential reservoir for bacteria.
D Avoiding direct pressure on the wound facilitates healing.
E The administration of granulocyte-stimulating factors (GSFs) results in faster resolution of the infection.
Ref.: 14
Comments
Diabetic patients have a higher risk for foot infections because of factors such as vascular insufficiency, decreased sensation, hyperglycemia, and impairment of the immune system, particularly neutrophil dysfunction. Deep tissue biopsy of the infected foot is the preferred method of culture. Acute diabetic foot infections are often caused by monomicrobial aerobic gram-positive cocci (S. aureus and β-hemolytic streptococci, especially group B), whereas patients with chronic wounds and those who have recently received antibiotic therapy generally have polymicrobial gram-positive and gram-negative aerobes and anaerobes within their wound, including enterococci, Enterobacter, obligate anaerobes, and P. aeruginosa. Initial therapy is usually empirical and based on the severity of infection and available microbiology data (culture results or Gram stain). A majority of mild infections can be treated with orally dosed antimicrobials directed against aerobic gram-positive cocci. In patients with more severe infections or extensive chronic infections, parenteral broad-spectrum antibiotics with activity against gram-positive cocci (including MRSA) and gram-negative and obligate anaerobic organisms is warranted. The diagnosis of infection in patients with chronic wounds includes the presence of purulent secretions (pus) and two or more of the following: redness, warmth, swelling or induration, and pain or tenderness. MRSA infections are associated with worse outcomes, and impaired host defenses allow low-virulence colonizers such as coagulase-negative staphylococci and Corynebacterium spp. to become pathogens. In addition to antibiotics, early incision and drainage of abscesses with débridement of devitalized tissue, immobilization, and supportive care are important in the total management of a diabetic foot. In the presence of significant vascular insufficiency, revascularization of the distal end of the lower extremity may improve healing and prevent amputation. Radioactive studies using technetium-99 (bone scan) or gallium citrate or indium-labeled leukocyte scans have poor specificity and should not be performed routinely. MRI has become the imaging study of choice for diagnosing osteomyelitis (OM).
Continued used of antimicrobials is not warranted for the entire time that the wound is open or for the management of clinically uninfected ulceration either to enhance wound healing or as prophylaxis against infection. Local wound care with sharp débridement of necrotic or unhealthy tissue promotes wound healing and removes a potential reservoir of pathogens. Avoiding direct pressure on the wound and providing off-loading devices facilitate wound healing. Administration of granulocyte colony-stimulating factors (G-CSFs) does not accelerate the resolution of infection but may significantly reduce the need for operative procedures.
Answer
D
21 Which of the following clinical situations or laboratory results require systemic antifungal therapy?
A A single positive blood culture result obtained from an indwelling intravascular catheter
B Candida identified from a drain
C Oral candidiasis
D Candida isolated from a drain culture in a patient who recently underwent surgery for colonic perforation
E Mucocutaneous candidiasis
Ref.: 1
Comments
Candidemia is associated with significant morbidity (e.g., endocarditis, septic arthritis, and ophthalmitis) and mortality (approximately 40%). Management of candidemia, particularly in patients with intravascular devices, remains controversial. Although some patients—usually immunocompetent patients—spontaneously clear the bloodstream after removal of the intravascular device, other patients—particularly those who are immunosuppressed—have disseminated disease and require systemic antifungal therapy. There are no accurate diagnostic tests or methods for selecting high-risk patients to determine those who require systemic antifungal therapy. Therefore, all patients with at least one positive blood culture result for Candida should be treated with an antifungal agent. All nonsurgically implanted lines should be removed, and if continued central venous access is required, a new line should be placed at a new site (not exchanged over a guidewire). Some would attempt to sterilize the bloodstream without the removal of tunneled catheters or subcutaneous ports. However, in patients with persistent candidemia or septic shock, these devices should also be removed. Amphotericin B and fluconazole appear to have similar efficacy in the treatment of candidemia. Voriconazole and caspofungin are new antifungal agents that are also effective against Candida. These agents may be particularly useful for non-albicans species such as Candida krusei or Candida glabrata, which are less susceptible to fluconazole. All patients with candidemia should be evaluated for manifestations of disseminated disease, such as ocular involvement or OM. Candida identified from a surgical drain most likely represents colonization and does not require systemic antifungal therapy. Mucocutaneous candidiasis can be treated with local nystatin or clotrimazole.
Answer
A
22 Which of the following statements regarding antifungal agents is false?
A Voriconazole is at least as effective as amphotericin B against invasive aspergillosis.
B Intravenous voriconazole is relatively contraindicated in patients with renal failure.
C Voriconazole causes irreversible changes in vision.
D Caspofungin is at least as effective as amphotericin B for the treatment of invasive candidiasis and, more specifically, candidemia.
E Caspofungin is not effective in the treatment of cryptococcal meningitis.
Ref.: 15, 16
Comments
Voriconazole is a broad-spectrum triazole that is active against Aspergillus spp. It is a selective inhibitor of the fungal cytochrome P-450 system used in the production of ergosterol for synthesis of the cell membrane. A randomized trial comparing voriconazole with amphotericin B for primary treatment of invasive aspergillosis showed that initial therapy with voriconazole led to better responses and improved survival. The survival rate at 12 weeks was 70.8% in the voriconazole group and 57.9% in the amphotericin B group, and voriconazole resulted in fewer severe side effects than did amphotericin B. In patients with a creatinine clearance rate of less than 50 mL/min, voriconazole should be given orally (not intravenously) since the intravenous vehicle (cyclodextrin) may accumulate and cause liver failure. Patients receiving voriconazole may experience episodes of visual changes, which are reversible.
Caspofungin is an echinocandin with an antifungal spectrum that includes Candida and Aspergillus spp., but not Cryptococcus neoformans. Caspofungin inhibits the synthesis of β-(1-3)-D-glycan, an essential component of the cell wall that is present in susceptible organisms. A recent study showed that the clinical outcome with caspofungin was similar to that with amphotericin B for the primary treatment of invasive candidiasis and candidemia.
Answer
C
23 Match each clinical characteristic or agent in the left-hand column with the correct infecting organism or organisms in the right-hand column.
|
A. Fibrosing mediastinitis |
a. Candida albicans |
|
B. Amphotericin |
b. Nocardia asteroides |
|
C. Intertrigo |
c. Actinomyces israelii |
|
D. Brain abscess |
d. C. neoformans |
|
E. Pelvic mass |
e. Histoplasma capsulatum |
Ref.: 1, 17
Comments
Amphotericin B remains an important agent for the treatment of systemic mycotic infections, including candidiasis, mucormycosis, cryptococcosis, histoplasmosis, coccidioidomycosis, sporotrichosis, and aspergillosis. Amphotericin B is a fungicidal agent. Binding of amphotericin B to ergosterol in the fungal cell membrane alters permeability, with leakage of intracellular ions and macromolecules leading to cell death. Adverse events such as infusion reactions and nephrotoxicity are common with the conventional (deoxycholate) form of the drug. New lipid formulations of amphotericin B have been developed and are associated with a reduction in toxicity without sacrificing efficacy. Newer triazoles (voriconazole and posaconazole) and echinocandins (caspofungin, micafungin, and anidulafungin) are emerging as alternative broad-spectrum antifungal agents. Histoplasmosis is predominantly a pulmonary infection caused by H. capsulatum, a dimorphic fungus endemic to the Mississippi and Ohio River valleys and along the Appalachian Mountains. Histoplasmosis has been associated with massive enlargement of the mediastinal lymph nodes secondary to granulomatous inflammation. During the healing process, fibrotic tissue can cause postobstructive pneumonia or constriction of the esophagus or superior vena cava and result in dysphagia or superior vena cava syndrome (or both). Actinomycosis is caused by a group of gram-positive higher-order bacteria that are part of the normal flora found in the oral cavity, gastrointestinal tract, and female genital tract. Typically, infections with Actinomyces spp. often occur after disruption of mucosal surfaces and lead to oral and cervical disease, pneumonia with empyema, and intraabdominal or pelvic abscesses. Placement of intrauterine devices has been associated with pelvic abscess secondary to this organism. Sinus tract formation is common as these organisms extend, unrestricted, through tissue planes. High-dose penicillin and surgical drainage are generally required for cure. Nocardia spp., other higher-order bacteria, are found in soil, organic matter, and water. Human infection occurs after inhalation or skin inoculation. Chronic pneumonia can occur, usually in immunocompromised patients. Skin lesions and brain abscesses are common with disseminated infection.
Prolonged treatment with sulfonamides in combination with other antibiotics is required for cure. C. neoformans causes meningitis and pulmonary disease. Infection is common in the setting of immunodeficiency, such as organ transplantation and AIDS, but it may also occur in immunocompetent hosts. C. albicans is a common inhabitant of the mucous membranes and gastrointestinal tract. Intertrigo is one form of cutaneous candidiasis that occurs in skinfolds where a warm moist environment exists. Vesiculopustules develop, enlarge, rupture, and cause maceration and fissuring. Obese and diabetic patients are at risk for the development of candidal intertrigo. Local care, including nystatin powder, is usually effective.
Answer
A-e; B-a,d,e; C-a; D-b; E-c
24 Which of the following statements is correct regarding spontaneous bacterial peritonitis (SBP; primary peritonitis) in a cirrhotic patient?
A Infection is usually polymicrobial.
B Ascitic fluid culture results are always positive.
C The most likely pathogenic mechanism is translocation from the gut.
D Twenty-one days of antibiotic treatment may be adequate.
E Infection-related mortality has declined to less than 10%.
Ref.: 18, 19
Comments
Spontaneous bacterial peritontis is a monomicrobial infection, with enteric gram-negative rods accounting for 60% to 70% of episodes of SBP. E. coli is the most frequently recovered pathogen, followed by K. pneumoniae. Streptococcal species, including pneumococci and enterococci, are also important pathogens. Ascitic fluid culture results are negative in many cases, but inoculation of blood culture bottles at the bedside yields bacterial growth in approximately 80% of cases. SBP most likely develops from the combination of prolonged bacteremia secondary to abnormal host defense, intrahepatic shunting, and impaired bactericidal activity of ascetic fluid. Transmural migration of gut flora and transfallopian spread of vaginal bacteria to the peritoneal space may also occur. Initial antimicrobial treatment should include coverage against aerobic gram-negative organisms. A third-generation cephalosporin, such as cefotaxime or ceftriaxone, is a reasonable choice. The duration of antibiotic treatment is unclear. Two weeks has been suggested, but shorter courses (5 days) may have similar efficacy. Although the in-hospital mortality rate approaches 40%, infection-related mortality has declined significantly (10%). Unfortunately, the probability of recurrence is 70% at 1 year, with 1- and 2-year survival rates being 30% and 20%, respectively.
Answer
E
25 Which of the following patients with cirrhosis benefit from prophylactic antibiotic therapy to decrease the risk for SBP?
A Patients awaiting liver transplantation
B Patients hospitalized with acute gastrointestinal bleeding
C Patients with ascitic fluid protein levels of greater than 1 g/100 mL
D Patients who have recovered from a previous episode of SBP
E Patients with ascitic fluid protein levels of less than 1 g/100 mL
Ref.: 19
Comments
Randomized trials have demonstrated that secondary prophylaxis with oral norfloxacin, 400 mg/day, or trimethoprim/sulfamethoxazole, one double strength tablet five times per week decreases the risk for recurrent spontaneous bacterial peritontis from 68% to 20%. However, overall mortality in these patients is unchanged in comparison to those not receiving secondary prophylaxis. Another observation is that long-term quinolone use has been associated with the development of infection with quinolone-resistant bacteria. In approximately 30% to 40% of patients with cirrhosis hospitalized for acute gastrointestinal bleeding, infection develops during the hospitalization. Norfloxacin (400 mg a day for 7 days) decreased the incidence of infective episodes involving gram-negative bacteria. The risk for SBP increases tenfold in patients with an ascitic fluid protein concentration of less than 1 g/100 mL fluid. Norfloxacin, 400 mg/day, during hospitalization decreases the incidence of SBP in these patients as well. Patients hospitalized while awaiting liver transplantation are probably at risk for SBP and may therefore benefit from antibiotic prophylaxis. Active infection is a contraindication to liver transplantation.
Answer
C
26 Which of the following statements regarding secondary peritonitis is false?
A It usually occurs as a result of perforation of an intraabdominal viscus.
B Carbapenems, aminoglycosides, and fourth-generation cephalosporins have equal efficacy in treatment studies.
C Increased age, cancer, cirrhosis, and systemic illness are factors that increase the mortality rate.
D Sequestration of bacteria within fibrin clots leads to intraabdominal abscess formation.
E The most common organism cultured from the abdomen is E. coli.
Ref.: 1, 13
Comments
Secondary peritonitis usually occurs as a result of perforation of an intraabdominal viscus: perforated peptic ulcer, appendix, or diverticulum or penetrating gastrointestinal trauma. The infection is polymicrobial, with facultative aerobes and anaerobes acting synergistically. One study revealed an average of 2.5 anaerobes and 2 facultative aerobes identified per case of secondary peritonitis. E. coli is the most common isolate in culture. Bacteroides spp. are the most frequent anaerobes cultured from abdominal infections. About 1012 bacteria reside in the colon per gram of feces, with 90% of these bacteria being anaerobic organisms. Any process that impairs immunologic function or is associated with general debilitation increases mortality. Age, cancer, hepatic cirrhosis, and the presence of a systemic illness have been shown to increase mortality. One of the defense mechanisms of the peritoneal cavity is the production of fibrin to sequester bacteria for limiting systemic spread. Such sequestration leads to the formation of intraabdominal abscesses, which generally require drainage for cure. Treatment of secondary peritonitis requires surgical intervention for removal of the source of infection and systemic antibiotics for eradication of residual bacteria. Antibiotics selected should include agents with broad-spectrum coverage for facultative aerobes, gram-negative bacilli, and anaerobes. Carbapenems are a good empirical choice for treatment. Aminoglycosides and fourth-generation cephalosporins lack anaerobic activity.
Answer
B
27 A 32-year-old HIV-positive intravenous drug user is admitted to the hospital following a seizure. Examination reveals a right pronator drift. MRI of the brain reveals two ring-enhancing lesions. All of the following diagnoses should be considered except:
A Progressive multifocal leukoencephalopathy (PML)
B Glioblastoma multiforme
C Toxoplasmosis
D Lymphoma
E Bacterial endocarditis
Ref.: 8
Comments
With the widespread use of highly active antiretroviral therapy, the incidence of neurologic disease in HIV-infected individuals has declined. Major human immunodeficiency virus-related central nervous system diseases include the AIDS-dementia complex, meningitis, myelopathy, opportunistic infections (e.g., cryptococcosis, PML secondary to JCpoly omavirus, cytomegalovirus [CMV], herpes, and toxoplasmosis), and neoplasms (primary CNS lymphoma). For patients with advanced HIV disease (CD4+ T-cell count <100 cells/mm3) who have focal neurologic disease and ring-enhancing lesions on brain imaging, the two major diagnostic considerations are toxoplasmosis and primary CNS lymphoma. PML is also a possibility in AIDS patients, but CNS lesions are not usually associated with cerebral edema. In addition, one should consider non–HIV-associated conditions, including primary brain tumors such as glioma and bacterial brain abscesses, which may occur in the setting of bacterial endocarditis and intravenous drug abuse. Current management recommendations for HIV-infected patients with focal brain lesions include approximately 2 weeks of empirical therapy for toxoplasmosis, followed by brain biopsy if radiographic or clinical deterioration occurs.
Answer
A
28 Persistent Salmonella bacteremia has been diagnosed in a 68-year-old man with a history of diabetes, hypertension, and peripheral vascular disease. The patient’s only complaints are fever and back pain. Transesophageal echocardiography showed normal findings. Which of the following tests should be recommended to confirm the clinical suspicion?
A CT scan of the chest and abdomen
B Duplex ultrasound of the lower extremities
C Explorative laparotomy
D Bone marrow culture and stool culture
E No further tests warranted
Ref.: 1
Comments
The patient has persistent bacteremia without evidence of cardiac involvement. However, an endovascular infection, such as an infected aortic atherosclerotic aneurysm, is a probable diagnosis in this patient. S. aureus and Salmonella spp. are common pathogens infecting preexisting atherosclerotic vessels. MRI, CT scanning, and sonographic studies may reveal the presence of an aneurysm but often do not provide adequate preoperative detail. Nuclear studies, such as gallium- or indium-labeled leukocyte scans, may help localize intraarterial infection, but they have low sensitivity (<30%). Although antibiotic therapy is needed for this disease, the vascular lesion is rarely sterilized, and aneurysmal enlargement with rupture is the rule. A high index of suspicion is required for early diagnosis since mortality rates exceed 80% if rupture recurs. If possible, perioperative angiography is usually performed to better delineate the extent of the aneurysm and operative approach.
Answer
A
29 Which of the following regarding complicated intraabdominal infections is true?
A They can be treated with intravenous antibiotics to eliminate the need for more invasive interventions.
B Isolated bacteria from colonic perforations are often aerobic gram-negative organisms.
C The infectious isolates from acute necrotizing pancreatitis and colonic perforation are similar.
D Bowel injuries secondary to penetrating, blunt, or iatrogenic trauma repaired within 12 hours of injury require no more than 72 hours of antibiotics.
E Single-agent therapy is often inadequate.
Ref.: 20
Comments
Complicated intraabdominal infections are defined as infections that extend beyond the hollow viscus of origin into the peritoneal space and result in either peritonitis or abscess formation. These infections require either operative or percutaneous intervention in addition to the administration of antibiotics for resolution. For community-acquired infections, the pathogen isolated varies according to the location of the perforation along the gastrointestinal tract. More proximal infections are due to facultative and aerobic gram-positive and gram-negative organisms. Terminal ileum/colonic perforations result from facultative and obligate anaerobes such E. coli, enterococci, and streptococci. Infections resulting from necrotizing pancreatitis are due to pathogens similar to those found in colonic perforation infections. Bowel injuries caused by penetrating, blunt, or iatrogenic trauma and repaired within 12 hours of injury are adequately treated with 24 hours or less of antibiotics. Randomized prospective trials have demonstrated that single-agent therapies with β-lactam/β-lactamase inhibitor combinations, carbapenems, or cephalosporins are adequate in the treatment of complicated intraabdominal infections.
Answer
C
30 A patient with AIDS who has never been treated with antiretroviral therapy is admitted to the hospital after 2 weeks of fever with postprandial right upper quadrant pain. His serum alkaline phosphatase level is elevated, and a sonographic study of the gallbladder reveals a thickened gallbladder wall with pericholecystic fluid but no evidence of gallstones. Which of the following organisms is not commonly responsible for this clinical syndrome?
A CMV
B Cryptosporidium
C Campylobacter spp.
D Mycobacterium avium
E Rhodococcus equi
Ref.: 8
Comments
AIDS-associated cholangiopathy is a condition characterized by pain and cholestasis along with bile duct stenosis, similar to the clinical picture seen with sclerosing cholangitis. The condition may be idiopathic or associated with opportunistic biliary infection, most commonly with cryptosporidia. Other infectious causes include CMV, Microsporida, and Cyclospora. Treatment consists of antimicrobial drugs and relief of mechanical obstruction, usually by endoscopic methods (sphincterotomy, dilation, and stenting). Hepatic disease and elevated levels of liver enzymes are common in patients with HIV infection, particularly those with late-stage disease. Patients often have coexisting chronic infection with hepatitis B virus (HBV) or hepatitis C virus (HCV). A multitude of opportunistic infections may affect the liver, including Mycobacterium avium-intracellulare, CMV, and Candida albicans. These patients may have clinical findings similar to those with cholangiopathy but do not have the ductal changes detected on ultrasound or endoscopic retrograde cholangiographic studies.
Answer
E
31 A 45-year-old man infected with HIV is evaluated for a persistently symptomatic posterior anal fissure with associated edematous tags. His CD4+ T-cell count is 100 cells/mm3. Which of the following statements regarding surgical treatment are true?
A Wound healing is unaffected by the stage of HIV disease.
B Internal anal sphincterotomy is unlikely to cause incontinence.
C Internal anal sphincterotomy is contraindicated in HIV-positive patients.
D Operative morbidity is correlated with the CD4+ T-cell count.
E Unlike the general population, anal fissures in HIV-positive patients tend to be anterior rather than posterior.
Ref.: 21
Comments
Anorectal surgery in HIV-positive patients should be approached with caution and concern regarding wound healing during the postoperative period. A distinction should be made among HIV-negative patients, asymptomatic HIV-positive patients, and patients with AIDS. In the first two categories, wound healing can be expected to occur within the usual 6 weeks following the operation. A patient with symptomatic HIV disease, particularly those with CD4+T-cell counts of less than 200 cells/mm3, may have very poor healing. Only 12% are healed within the first month, and a third may take longer than 6 months to heal. Furthermore, if a sphincterotomy is performed, most patients will have some impairment of continence postoperatively. In light of these factors, a thorough evaluation of potential risk factors and, if possible, determination of HIV status are advised before proceeding with anorectal surgery in groups at high risk of becoming infected. CD4+ counts have been shown to be correlated with morbidity. Sixty-five percent morbidity rates have been seen in patients with CD4+ counts of less than 200 cells/mm3, as opposed to 7% morbidity rates in patients with counts greater than 200 cells/mm3. In summary, cautiously performed anorectal surgery in an asymptomatic HIV-positive patient is appropriate. Anorectal surgery in a patient with AIDS, however, may be followed by prolonged wound healing and functional impairment.
Answer
D
32 Which of the following previously healthy patients scheduled for an operation should undergo HIV antibody testing?
A A 35-year-old man seen for removal of a lipoma in the anterior triangle of the neck. A routine preoperative complete blood count reveals a white cell count of 4500 cells/mL with a normal differential, hemoglobin level of 13 g/dL, and platelet count of 81,000/mL.
B A 40-year-old man seen for repair of an inguinal hernia. Physical examination reveals white, adherent, nonremovable plaques on the lateral aspect of his tongue.
C A 28-year-old woman seen for removal of a breast lump in whom a painful vesicular rash along the T8-10 dermatomes develops on the right side.
D A 20-year-old man undergoing nephrectomy for living related donor transplantation.
E All of the above.
Ref.: 1
Comments
Several risk groups have been identified in whom human immunodeficiency virus testing is indicated, including persons with sexually transmitted diseases and persons in high-risk categories, such as injected drug users, homosexual and bisexual men, hemophiliacs, patients with active tuberculosis (TB), and pregnant women. Donors of blood or organs should be tested. Certain clinical or laboratory findings should also prompt HIV testing. Such findings include idiopathic thrombocytopenia, oral hairy leukoplakia, reactivation varicella-zoster virus infection involving more than one dermatome, unexplained oral candidiasis, persistent vulvovaginal candidiasis, and herpes simplex virus infection resistant to treatment.
Answer
E
33 Which of the following statements about HIV-positive patients with gastrointestinal bleeding is incorrect?
A The most common cause of lower gastrointestinal bleeding is CMV colitis.
B Ganciclovir therapy prevents rebleeding in patients with documented CMV disease.
C Kaposi sarcoma is the most frequent AIDS-associated cause of upper gastrointestinal bleeding.
D Upper gastrointestinal bleeding is usually secondary to infection.
E Lower gastrointestinal bleeding is less common than upper gastrointestinal bleeding.
Ref.: 22
Comments
Gastrointestinal bleeding is a relatively infrequent complication in human immunodeficiency virus-infected individuals. Upper gastrointestinal bleeding is more frequent than lower gastrointestinal hemorrhage and is usually unrelated to HIV infection (e.g., caused by peptic ulcer disease, esophageal varices secondary to portal hypertension, or a Mallory-Weiss tear). However, in patients with advanced HIV infection, AIDS-associated causes such as Kaposi sarcoma become more common. Cytomegalovirus infection can produce disease at all levels of the gastrointestinal tract and is the most common cause of colitis and lower gastrointestinal hemorrhage in AIDS patients. Ganciclovir is effective therapy for CMV disease of the gastrointestinal tract and prevents recurrent hemorrhage. Significant bone marrow suppression with neutropenia is a frequent side effect of ganciclovir therapy. In stable patients, endoscopy with biopsy is the initial diagnostic procedure of choice for HIV-infected patients with gastrointestinal bleeding.
Answer
D
34 Patient factors that have been shown to increase the risk for postoperative infection include all of the following except:
A Diabetes mellitus
B Nicotine use
C Prolonged hospitalization before surgery
D Obesity
E S. aureus carrier status
Ref.: 23, 24
Comments
Patients with elevated hemoglobin A1c levels have an increased incidence of surgical site infections after cardiac surgery. Nicotine impedes wound healing, which is thought to increase the risk for SSIs. Current smoking is an independent risk factor for mediastinal or sternal wound infections following cardiac surgery. Postoperative infections are at least twice as likely to develop in carriers of S. aureus as in noncarriers. Other important factors are advanced age, ischemia secondary to vascular disease, previous radiation exposure, and obesity. The length of the preoperative hospital stay is a much less significant problem than in previous years.
Answer
C
35 Which of the following statements regarding CMV infection and solid organ transplantation is false?
A Symptomatic infection occurs 2 to 6 months after transplantation.
B Patients being treated for acute rejection are at increased risk for the development of symptomatic CMV infection.
C Transmission can occur through the donor organ.
D Reactivation of latent infection is associated with the greatest risk for the development of severe disease.
E CMV infection may be associated with premature atherosclerosis in cardiac transplant patients.
Ref.: 25, 26
Comments
Cytomegalovirus is the most important pathogen affecting recipients of solid organ transplants. Symptomatic CMV disease may develop in as many as 50% of allograft recipients, usually 2 to 6 months after transplantation. CMV-seronegative recipients who are primarily infected are at greatest risk for the development of severe CMV disease. Primary infection can occur through the donor organ, unscreened blood products, or intimate contact with a viral shedder. Reactivation of latent infection is less likely to cause severe disease. Patients receiving Muromonab CD-3 (OKT3)/antilymphocyte globulin (ALG) therapy for acute rejection also appear to be at risk for the development of CMV disease. In addition to clinical disease directly attributable to CMV infection, CMV has indirect immunomodulatory activity. Symptomatic CMV infections are associated with an increased incidence of bacterial infections and opportunistic infections such as aspergillosis and Pneumocystis carinii pneumonia. In heart transplant patients, acute rejection and accelerated atherosclerosis are associated with CMV infection. Ganciclovir is the most commonly used agent for the prevention of CMV infection and disease; however, there is growing concern regarding the emergence of ganciclovir resistance.
Answer
D
36 A 28-year-old man who sustained closed head trauma in a motor vehicle accident a month earlier comes to the emergency department with a 3-day history of progressive headache, fever, and confusion. His wife reports the recent onset of clear drainage from his left naris. Physical examination reveals a temperature of 102° F (38.9° C), a stiff neck, and no rash. Which of the following statements concerning the patient is true?
A He most likely has bacterial meningitis secondary to S. aureus.
B Antiretroviral prophylaxis has been beneficial in preventing bacterial meningitis after head trauma.
C Empirical antibiotics should include an extended-spectrum cephalosporin and vancomycin.
D Corticosteroid administration with antibiotics is not indicated.
E He requires immediate surgical intervention for repair of cerebrospinal fluid leakage.
Ref.: 27, 28
Comments
The patient probably sustained a basilar skull fracture and a dural rent, with subsequent development of a dural fistula from the subarachnoid space and nasal cavity or paranasal sinuses. Cerebrospinal fluid rhinorrhea may occur and can easily be diagnosed by detecting the presence of β2-transferrin in nasal secretions. In patients with known basilar skull fracture, cerebrospinal fluid rhinorrhea develops in approximately 10%. Of these patients, bacterial meningitis develops in up to 30%. S. pneumoniae is the most common pathogen (65% of cases). Other organisms, such as H. influenzae, Neisseria meningitidis, and S. aureus, account for the remaining cases. Empirical treatment should include an extended-spectrum cephalosporin (ceftriaxone, cefotaxime, or cefepime) and vancomycin since the incidence of β-lactam–resistant pneumococci is increasing. Prophylactic antibiotics have no proven benefit and may predispose to meningitis from antibiotic-resistant gram-negative bacteria. A recent prospective study demonstrated a survival advantage in patients with pneumococcal meningitis who received corticosteroids before or at the time of antibiotic administration. Spontaneous closure of the dural fistula is less likely in patients with a delayed manifestation of cerebrospinal fluid leakage with meningitis, and surgical repair is indicated. Diagnostic studies to identify the site of the fistula and treatment of any CNS infection should be completed before surgical intervention.
Answer
C
37 A large painful swelling in the right inguinal area has developed in a 25-year-old man who recently returned from Southeast Asia. He admits to having unprotected sex during his visit, and a small painless ulcer had developed on his penis and healed without a scar 2 weeks earlier. Physical examination reveals a temperature of 102° F (38.9° C) and firm right inguinal adenopathy with areas of fluctuance. Which of the following is appropriate in the management of this patient?
A Obtain an incisional biopsy specimen of the inguinal nodes.
B Perform serologic tests for Chlamydia trachomatis, syphilis, and HIV.
C Start oral penicillin.
D Perform a CT scan of the chest and abdomen for staging of the disease.
E Perform a PET scan to rule out lymphoma.
Ref.: 1
Comments
Few sexually transmitted diseases are characterized by inguinal lymphadenopathy with or without associated ulcers involving the genitalia. These diseases include lymphogranuloma venereum (LGV), syphilis, granuloma inguinale, chancroid, and sometimes herpes simplex. The findings in this patient are classic for LGV, which is caused by C. trachomatis serovars L1 to L3. LGV has three stages. Initially, there is a small, painless ulcer that heals without scarring, followed (in days to weeks) by discrete inguinal lymphadenopathy that is generally unilateral (in two thirds of cases). The swollen lymph nodes may coalesce to form abscesses and sinus tracts if untreated. Incisional biopsy is contraindicated in these patients because of the potential for sinus tract formation. Healing can occur without treatment as hardened inguinal masses develop and slowly involute. Relapse occurs in approximately 20% of untreated patients. The disease, which is endemic in Southeast Asia, Africa, India, South America, and the Caribbean Islands, is diagnosed by serologic testing and resolves with doxycycline, 100 mg twice daily for 21 days. The differential diagnosis of inguinal lymphadenopathy in this age group includes the sexually transmitted diseases mentioned earlier and sometimes lymphoma, but a CT scan is clearly not warranted at this stage.
Answer
B
38 Which of the following statements regarding HCV infection is false?
A The prevalence of HCV infection in health care workers (HCWs) is similar that in the general population.
B Chronic HCV infection occurs in 75% to 85% of patients after acute infection.
C Hepatic failure as a result of chronic HCV infection is the most common indication for liver transplantation.
D Pegylated interferon plus ribavirin is effective therapy for the majority of patients with chronic HCV infection.
E Factors associated with the development of cirrhosis include male gender, alcohol use, and coinfection with HIV.
Ref.: 1, 29
Comments
Persons with acute hepatitis C virus infection are typically asymptomatic (60% to 70%) or have mild clinical illness. Fulminant hepatitis is rare. Chronic HCV infection develops in approximately 75% to 80% of persons with acute HCV infection. Cirrhosis develops in 10% to 20% of chronically infected individuals, usually after more than 20 years of infection. Liver failure from chronic HCV infection has become the leading indication for liver transplantation. Increased alcohol use, male gender, HIV coinfection, and HCV genotype 1 are associated with more severe liver disease. Hepatocellular carcinoma can be a late complication in 1% to 2% of patients with cirrhosis. Antiviral therapy is recommended for individuals at increased risk for progressive liver disease, as demonstrated by persistently elevated serum transaminase levels, detectable HCV RNA levels, and moderate inflammation in liver biopsy specimens. The combination of pegylated interferon and ribavirin is the most effective regimen to date.
However, up to 60% of patients receiving this treatment fail to achieve a sustained virologic response. Predictors of a poor response include HCV genotype 1 (most frequent genotype in the United States), more extensive fibrosis in liver biopsy specimens, and high baseline HCV RNA levels. Adverse events (e.g., bone marrow suppression and fatigue) are common and significant and lead to discontinuation of combination therapy in 20% of patients. The prevalence of HCV infection is highest in injected drug users and patients undergoing hemodialysis. Overall, nearly 2% of the U.S. population has persistent HCV infection. Although transmission of HCV to HCWs occurs after approximately 3% of needlestick exposures involving HCV-infected patients, the prevalence of HCV infection in HCWs, including surgeons, is similar to that in the general population.
Answer
D
39 Which of the following markers is clinically useful for predicting progression to AIDS in persons infected with HIV-1?
A CD4+ T-cell count greater than 600 cells/mm3
B p24 antigen level
C HIV-1 RNA plasma viral load
D Serum neopterin level
E Serum β2-microglobulin level
Ref.: 1
Comments
The human immunodeficiency virus plasma viral load strongly predicts the rate of decrease in CD4+ T lymphocytes and progression to AIDS and death. Progression to AIDS within 6 years occurs in 80% of HIV-infected individuals with viral loads greater than 30,000 copies/mL, as compared with 55.2%, 31.7%, 16.6%, and 5.4% of individuals with viral loads of 10,000 to 30,000, 3001 to 10,000, 501 to 3000, and less than 500 copies/mL, respectively. The baseline viral load is a stronger predictor of progression of disease and outcome than is the CD4+ T-cell count. However, the combination of HIV load and CD4+T-cell count gives the best prognostic estimate for HIV-infected individuals. The CD4+ T-cell count reflects the degree of immunocompromise and is most useful for determining the risk for opportunistic infection. The normal CD4+ T-cell count is greater than 600 cells/mm3. Symptomatic HIV infection usually begins when CD4+ T-cell counts fall below 350 cells/mm3. Opportunistic infections, such as P. carinii pneumonia, occur when CD4+ T-cell counts fall below 200 cells/mm3. Without antiretroviral treatment, the median time from infection to the development of AIDS is approximately 11 years. p24 antigen is one of the major core proteins of HIV. It can be detected during the acute phase of HIV infection and during late symptomatic disease. Serum neopterin produced by macrophages stimulated by interferon and β2-microglobulin levels reflect lymphocytic turnover. Although both may be found in HIV-infected individuals, neither is specific for HIV infection.
Answer
C
40 Which statement about M. tuberculosis treatment and prophylaxis is true?
A Two-drug treatment with isoniazid (INH) and rifampin (RIF) for 9 months is standard therapy for active pulmonary TB.
B Treatment failure can be due to drug resistance or nonadherence.
C HIV-infected individuals require prolonged therapy for active TB.
D INH prophylaxis for latent TB is given for at least 12 months.
E INH prophylaxis should not be given to individuals with recent conversion from purified protein derivative (PPD)-negative to PPD-positive status.
Ref.: 30
Comments
Recent Centers for Disease Control and Prevention (CDC) guidelines recommend that all patients with active pulmonary tuberculosis receive four-drug therapy consisting of INH, RIF, pyrazinamide, and ethambutol for the initial 2 months of treatment. For patients with drug-susceptible TB and negative sputum test results after 2 months of therapy, treatment can be completed with 4 months of INH and RIF. Extrapulmonary disease requires 6 to 9 months of treatment, except for meningitis, which is treated for 1 year. HIV-infected individuals are treated similar to non–HIV-infected patients with TB. However, significant drug-drug interactions may occur with antiretroviral agents and TB drugs and may alter therapeutic decisions. Treatment failures are generally due to nonadherence by patients to multidrug regimens. Currently, local health departments have directly observed therapy programs to improve compliance with and completion of anti-TB medication regimens. Another cause of treatment failure is infection with multidrug-resistant strains of Mycobacterium tuberculosis. Conditions associated with a higher rate of resistance include TB in those known to have a higher prevalence of drug resistance, such as Asians or Hispanics and previously treated individuals; persistence of culture-positive sputum after 2 months of therapy; and known exposure to drug-resistant TB.
Certain individuals are at considerable risk for the development of active TB once infected (latent TB). TB skin testing (Mantoux/PPD) is useful for identifying latent TB in high-risk individuals. Three cut points have been recommended for defining a positive tuberculin reaction: greater than 5 mm, greater than 10 mm, and greater than 15 mm of induration. Persons considered at highest risk (>5 mm of induration) include individuals with HIV infection, recent contacts with TB patients, and organ transplant patients. Individuals also at risk (>10-mm induration) include injected drug users, residents of nursing homes and prisons, hospital employees, and recent immigrants from countries with a high prevalence of TB. These individuals, who are at considerable risk for the development of active TB once infected, should receive 9 months of INH therapy.
Answer
B
41 A 50-year-old woman with a history of severe dilated cardiomyopathy and placement of a left ventricular assist device (LVAD) is admitted to the hospital with fever and S. aureus bacteremia. Which of the following statements regarding LVAD-associated infection is not true?
A LVAD-associated infection is a common event that occurs in up to 50% of LVAD recipients.
B LVAD-associated bacteremia is a contraindication to cardiac transplantation.
C The majority of LVAD-associated infections occur within 1 month of implantation.
D Gram-positive bacteria are responsible for most LVAD-associated bacteremias.
E The optimal duration of antibiotic therapy for LVAD-associated bacteria is poorly defined.
Ref.: 31
Comments
Left ventricular assist device implantation has become an effective means of treating severe heart failure in patients awaiting cardiac transplantation. Unfortunately, device-related infection is common and occurs in nearly 50% of LVAD recipients. Localized infections involving the drive line exit site or LVAD pocket occur but are frequently associated with bacteremia. The majority (60%) of LVAD-associated infections occur within 30 days of implantation. Gram-positive bacteremia accounts for more than 75% of infections, with staphylococci being the most frequent blood isolate. Although short courses of systemic antibiotics for localized infections may be curative, the optimal duration of antibiotic therapy for LVAD-associated bacteremia is unclear. Relapse is common, and systemic antibiotics should generally be continued through transplantation.
Transplantation is not contraindicated in patients with recent LVAD-associated bacteremia. Posttransplant outcomes, such as length of hospitalization and 1-year survival rates, are not different in infected and noninfected LVAD patients.
Answer
C
42 Suspicion of OM in a diabetic foot ulcer should be raised in all of the following except:
A Deep ulcer that overlies a bony prominence
B An ulcer that does not heal after 2 weeks of appropriate therapy
C A patient with a swollen foot and a history of foot ulceration
D Unexplained high white blood cell count or inflammatory markers in a patient with a diabetic foot ulcer
E Evidence of cortical erosion and periosteal reaction on plain radiography
Ref.: 14
Comments
See Question 43.
Answer
B
43 Which of the following is true regarding OM in a diabetic foot?
A A nuclear medicine tagged white blood cell scan is the best way to diagnose OM.
B The only reported successful treatment of OM includes resection of the infected bone.
C A presumptive diagnosis of OM cannot be made even if bone destruction is seen on plain film underneath an ulcer.
D Bone biopsy is often difficult to perform and invasive and should be avoided.
E Selected patients may benefit from implanted antibiotics, hyperbaric oxygen therapy, or revascularization.
Ref.: 14
Comments
Osteomyelitis impairs healing of the wound and acts as a nidus for recurrent infection. It should be suspected in any deep or extensive ulcer, in one that overlies a bony prominence, and in an ulcer that does not heal after 6 weeks of appropriate therapy. In addition, concern for OM is raised in a patient with a swollen foot and a history of foot ulceration, the presence of a “sausage toe” (red, swollen digit), unexplained high white blood cell count, or inflammatory markers. Bone destruction underneath an ulcer seen on radiographs or probing of an ulcer down to bone is OM until proved otherwise. MRI is the most useful available imaging modality to diagnose OM, as well as to characterize any underlying soft tissue infection. The “gold standard” for diagnosis of OM remains isolation of bacteria from a bone sample with concomitant histologic findings of inflammatory cells and osteonecrosis.
When treating a diabetic foot infection, if there are no hard signs to indicate the presence of OM and plain radiographs do not demonstrate any evidence of bone pathology, the patient should be treated for about 2 weeks for the soft tissue infection. If there is persistent concern for OM, plain films should be repeated in 2 to 4 weeks to look for evidence of cortical erosion, periosteal reaction, or mixed radiolucency and sclerosis. Radioisotope scans are more sensitive than plain radiographs for diagnosis but are expensive and can be time consuming. If findings on plain films are only consistent with but not characteristic of OM, the clinician should consider the following: (1) additional imaging studies—MRI is preferred but nuclear medicine scans with leukocyte or immunoglobulin techniques would be the second choice; (2) empirical treatment for an additional 2 to 4 weeks with repeated radiographs to look for progression of bone changes; and (3) bone biopsy (operative or percutaneous fluoroscopic or CT guidance), especially if the etiologic pathogen or susceptibilities need to be established. Some physicians would perform biopsies for midfoot or hindfoot lesions because these are more difficult to treat and lead to higher-level amputations.
Traditionally, resection of a bone with chronic OM was necessary for cure; however, some nonrandomized case series report clinical success in 65% to 80% of patients treated nonoperatively with prolonged (3 to 6 months) antibiotic therapy. When treatment of OM fails, the clinician should consider whether the original diagnosis was correct, whether there is any remaining necrotic or infected bone or surgical hardware that needs to be removed, and whether the antimicrobials selected were appropriate, achieved an effective concentration within the bone, and were used for a sufficient duration. Selected patients may benefit from implanted antibiotics, hyperbaric oxygen therapy, revascularization, long-term or intermittent antibiotic administration, or amputation.
Answer
E
44 Which of the following regarding hospital-acquired pneumonia (HAP), ventilator-associated pneumonia (VAP), and health care–associated pneumonia (HCAP) is false?
A They are the most common nosocomial infection.
B They are usually caused by aerobic gram-negative bacilli.
C They are rarely due to viral or fungal pathogens in immunocompetent patients.
D Infection resulting from aspiration is usually due to anaerobes.
E Gram-positive coccal isolates are more common patients with head trauma.
Ref.: 32
Comments
See Question 45.
Answer
A
45 Which of the following are risk factors for HAP, VAP, or HCAP caused by multidrug-resistant pathogens?
A Hospitalization for 5 or more days
B Antimicrobial therapy or hospitalization in the preceding 90 days
C Home wound care
D Immunosuppressive disease or therapy
E All of the above
Ref.: 32
Comments
HAP, HCAP, and VAP are the second most common nosocomial infections after urinary tract infection. They result in significant morbidity and mortality. They are due to a wide spectrum of bacterial pathogens and are often polymicrobial, especially in patients with acute respiratory distress syndrome. They are rarely due to viral or fungal agents in immunocompetent patients. Isolation of Candida from endotracheal aspirates of immunocompetent patients usually represents colonization.
Common pathogens include aerobic gram-negative bacilli, including P. aeruginosa, E. coli, K. pneumoniae, and Acinetobacter spp. There has been an emergence of pneumonia associated with gram-positive cocci (S. aureus, particularly MRSA), and it is more commonly seen in diabetics, patients with head trauma, and those hospitalized in the intensive care unit. Infection with anaerobic organisms may follow aspiration in nonintubated patients but is rare in VAP.
Early-onset HAP or VAP occurring within the first 4 days of hospitalization carries a better prognosis than does late-onset infections (5 days or more), which are more likely to be due to multidrug-resistant bacterial pathogens and result in increased morbidity and mortality. Additional risk factors for multidrug-resistant bacterial pathogens such as Pseudomonas, Acinetobacter spp., MRSA, and K. pneumoniaeinclude antimicrobial therapy or hospitalization in the preceding 90 days, a high frequency of antibiotic resistance in the community or in the specific hospital unit, and immunosuppressive disease or therapy. Risk factors for multidrug-resistant pathogens in patients with HCAP include residence in a nursing home or long-term care facility, home infusion therapy, chronic dialysis within 30 days, home wound care, and a family member with a multidrug-resistant pathogen.
P. aeruginosa is the most common gram-negative bacterial pathogen that causes multidrug-resistant HAP/VAP, with some isolates being susceptible only to polymyxin B. Most MRSA infections are treated successfully with linezolid, although MRSA isolates resistant to linezolid are emerging.
Early administration of a broad-spectrum antibiotic in adequate doses and deescalation of the initial antibiotic therapy on the basis of cultures and clinical response are essential. Failure to adequately treat the infection because of delayed initiation of appropriate therapy has been associated with increased mortality. Guidelines have been established by the American Thoracic Society and the Infectious Disease Society of America for empirical therapy in immunocompetent adults with bacterial causes of HAP, VAP or HCAP; treatment should include either ceftriaxone, a fluoroquinolone, ampicillin/sulbactam, or ertapenem if there is no suspicion of a multidrug-resistant pathogen.
Answer
E
References
1 Mandell GL, Bennett JE, Dolin R. Principles and practice of infectious diseases, ed 5. Philadelphia: Churchill Livingstone; 2000.
2 Chen SC, Wu WY, Yeh CH, et al. Comparison of Escherichia coli and Klebsiella pneumonia liver abscesses. Am J Med Sci. 2007;334:97-105.
3 Suerbaum S, Michetti P. Helicobacter pylori infection. N Engl J Med. 2002;347:1175-1186.
4 Bernard GR, Vincent JL, Laterre PF, et al. Efficacy and safety of recombinant human activated protein C for severe sepsis. N Engl J Med. 2001;344:699-709.
5 ASHP therapeutic guidelines on antimicrobial prophylaxis in surgery. American Society of Health-System Pharmacists. Am J Health Syst Pharm. 1999;56:1839-1888.
6 Barie PS. Surgical site infections: epidemiology and prevention. Surg Infect (Larchmt). 2002;3(Suppl 1):9-21.
7 Wilson W, Taubert KA, Gewitz M, et al. Prevention of infective endocarditis: guidelines from the American Heart Association. J Am Dent Assoc. 2007;138:739-745.
8 Dolin R, Masur H, Saag MS. AIDS therapy, ed 2. Philadelphia: Churchill Livingstone; 2003.
9 Magadia RR, Weinstein MP. Laboratory diagnosis of bacteremia and fungemia. Infect Dis Clin North Am. 2001;15:1009-1024.
10 Karageorgopoulos DE, Falagas ME. New antibiotics: optimal use in current clinical practice. Int J Antimicrob Agents. 2009;34(Suppl 4):S55-S62.
11 Kretsinger K, Broder KR, Cortese MM, et al. Preventing tetanus, diphtheria, and pertussis among adults: use of tetanus toxoid, reduced diphtheria toxoid and acellular pertussis vaccine. MMWR Recomm Rep. 2006;55(RR-17):1-37.
12 Katzung BG. Basic and clinical pharmacology, ed 8. New York: McGraw-Hill; 2001.
13 Anaya DA, Dellinger EP. Surgical infections and choice antibiotics. In Townsend CM, Beauchamp RD, Evers BM, et al, editors: Sabiston textbook of surgery: the biological basis of modern surgical practice, ed 18, Philadelphia: WB Saunders, 2008.
14 Lipsky BA, Berendt AR, Deery HG, et al. Diagnosis and treatment of diabetic foot infections. Clin Infect Dis. 2004;39:885-910.
15 Mora-Duarte J, Betts R, Rotstein C, et al. Comparison of caspofungin and amphotericin B for invasive candidiasis. N Engl J Med. 2002;347:2020-2029.
16 Herbrecht R, Denning DW, Patterson TF, et al. Voriconazole versus amphotericin B for primary therapy of invasive aspergillosis. N Engl J Med. 2002;347:408-415.
17 Garrett HEJr, Roper CL. Surgical intervention in histoplasmosis. Ann Thorac Surg. 1986;42:711-722.
18 Bhuva M, Ganger D, Jenssen D. Spontaneous bacterial peritonitis: an update on evaluation, management, and prevention. Am J Med. 1994;97:169-175.
19 Such J, Runyon BA. Spontaneous bacterial peritonitis. Clin Infect Dis. 1998;27:669-674.
20 Solomkin JS, Mazuski JE, Baron EJ, et al. Guidelines for the selection of anti-infective agents for complicated intra-abdominal infections. Clin Infect Dis. 2003;37:997-1005.
21 Beck DE, Wexner SD. Fundamentals of anorectal surgery. New York: McGraw-Hill; 1992.
22 Chalasani N, Wilcox CM. Gastrointestinal hemorrhage in patients with AIDS. AIDS Patient Care STDs. 1999;13:343-346.
23 Arnold MA, Barbul A. Surgical site infections. In Cameron JL, editor: Current surgical therapy, ed 9, Philadelphia: CV Mosby, 2008.
24 Cheadle WG. Risk factors for surgical site infection. Surg Infect (Larchmt). 2006;7:S7-S11.
25 Simon DM, Levin S. Infectious complications of solid organ transplantations. Infect Dis Clin North Am. 2001;15:521-549.
26 Razonable RR: Infections in solid organ transplant recipients. Conference report: highlights from the 40th annual meeting of Infectious Diseases Society of America, October 24–27, 2002.
27 de Gans J, van de Beek D. Dexamethasone in adults with bacterial meningitis. N Engl J Med. 2002;347:1549-1556.
28 Chawdhury MH, Tunkel AR. Antibacterial agents in infections of the central nervous system. Infect Dis Clin North Am. 2000;14:391-408.
29 Centers for Disease Control and Prevention. Recommendations for prevention and control of hepatitis C virus infection and HCV-related chronic disease. MMWR Recomm Rep. 1998;47(RR-19):1-39.
30 American Thoracic Society; CDC; Infectious Diseases Society of America. Treatment of tuberculosis. MMWR Recomm Rep. 2003;52(RR-11):1-77.
31 Argenziano M, Catenese KA, Moazami N, et al. The influence of infection on survival and successful transplantation in patients with left ventricular assist devices. J Heart Lung Transplant. 1997;16:822-831.
32 Guidelines for the management of adults with hospital-acquired, ventilator-associated, and healthcare-associated pneumonia. Am J Respir Crit Care Med. 2005;171:388-416.
B Transmissible Diseases and Surgeons
1 Which of the following is not considered standard precautions for reducing the spread of transmissible diseases?
A Hand washing before contact with a patient
B Hand washing after glove removal
C Wearing gloves during contact with a patient
D Negative pressure airflow
E Eye protection
Ref.: 1
Comments
Standard, or universal, precautions are designed to prevent the spread of transmissible disease by contact with blood, body fluids, or any other potentially infected material. These precautions apply to allpatients all of the time. Hand washing is fundamental and should be performed before and between each contact with a patient and after glove removal. Gloves are worn when contacting a potentially contaminated area. Surgical masks and eye protection are required if mucous membrane or eye exposure is possible. Gowns are part of standard precautions when more extensive blood or fluid exposure may occur. Specific engineering controls for airflow and processing of air are integral to preventing spread of certain airborne pathogens and as such are not a component of basic standard precautions. Specific procedures for infection control are mandated by federal regulatory agencies. Surgeons and all health care workers (HCWs) must be familiar with the specific infection control policies and procedures established at their places of work.
Answer
D
2 A 68-year-old woman is admitted to the hospital for neurosurgery after being found comatose at home. The patient lives alone, but her neighbor states that she has been “acting strangely” for the last several weeks. No additional history is available. MRI of the brain reveals evidence of focal cerebritis and enlarged ventricles along with enhancement of the basilar meninges. A chest radiograph shows upper lobe consolidation. Results of a rapid HIV test are positive. The patient is taken to the operating room for placement of a ventricular drain. Which type of isolation would be needed for this patient in the postoperative period?
A Standard and airborne precautions
B Airborne precautions
C Droplet precautions
D Contact precautions
E Reverse isolation
Ref.: 2
Comments
This human immunodeficiency virus-infected patient has evidence of meningitis, cerebritis, and upper lobe pneumonia. The unifying diagnosis is pulmonary and cerebral tuberculosis. This patient requires airborne precautions.
A variety of infection control measures are implemented to decrease the risk for transmission of microorganisms in hospitals. Standard precautions are used for the care of all patients. Hand washing between patient contact and the use of barrier protection, such as gloves, gowns, and masks, to minimize exposure to potentially infectious body fluids (e.g., blood, feces, wound drainage) are important components of standard precautions and all infection control programs.
In addition to standard precautions, airborne precautions are used for patients with known or suspected illness transmitted via small airborne droplets (≤5 µm). TB, measles, smallpox, and varicella (chickenpox) are examples of diseases requiring airborne precautions. Because these organisms can be dispersed widely by air currents and may remain suspended in the air for long periods, special air handling and ventilation are necessary. Patients requiring airborne precautions are placed in “negative pressure” rooms, and all persons entering the room require an N95 mask.
In addition to standard precautions, droplet precautions are used for patients with suspected or proven invasive disease caused by H. influenzae or N. meningitidis (e.g., pneumonia, meningitis, or sepsis) or other respiratory illnesses such as diphtheria, pertussis, pneumonic plague, influenza, mumps, and rubella. The droplets produced by these illnesses are usually generated by coughing but are larger than the droplets described earlier (>5 µm), travel only short distances (<3 feet), and do not remain suspended in air. Patients require a private room, and persons entering the room require a surgical mask.
In addition to standard precautions, contact precautions apply to specific patients infected or colonized with epidemiologically important organisms spread by direct contact with a patient or contact with items in the patient’s environment. These organisms may demonstrate antibiotic resistance and include MRSA, vancomycin-resistant S. aureus, VRE, and multidrug-resistant gram-negative bacilli. Enteric pathogens such as C. difficile and skin infections such as impetigo (group A streptococci), herpes simplex, and scabies also require contact precautions.
Answer
A
3 Which of the following statements regarding MRSA is false?
A MRSA is a common nosocomial pathogen, but it can also be detected in the community.
B The treatment of choice is vancomycin.
C Treatment of surgical patients with intranasal mupirocin decreases wound infection rates with MRSA.
D Hospitalized patients colonized with MRSA require contact isolation.
E MRSA is less virulent than methicillin-sensitive S. aureus.
Ref.: 3-5
Comments
Staphylococci are the most common cause of nosocomial infections in surgical patients. Recent reports suggest that carriage of methicillin-resistant S. aureus ™in the community has increased, and more infections with this organism are being seen in persons without health care–associated risks (nosocomial risks).
At the beginning of the antibiotic era, S. aureus was susceptible to penicillins. Resistance developed to penicillin via β-lactamase production, and new antibiotics were discovered, including the penicillinase-resistant penicillins (methicillin, oxacillin, nafcillin, etc). MRSA is by definition resistant to methicillin. Methicillin is not used in clinical practice because it induces interstitial nephritis, but it is still used in the laboratory to differentiate methicillin-susceptible S. aureus (MSSA) from MRSA. Vancomycin or linezolid can be used to treat MRSA. S. aureus strains with intermediate susceptibility to vancomycin and vancomycin-resistant S. aureus have been reported in the United States.
Although some studies suggest that mortality after MRSA infection is higher that that after methicillin-susceptible S. aureus infection, the increased death rate is most likely due to comorbid conditions and not to differences in virulence between MSSA and MRSA. Hospitalized patients colonized with MRSA require contact isolation to avoid spread of the bacteria to other patients. A recent prospective, randomized, placebo-controlled study showed that intranasal mupirocin did not significantly reduce S. aureus SSIs. However, it did significantly reduce the rate of all nosocomial S. aureus infections in the patients who were S. aureus carriers.
Answer
C
4 Which of the following statements regarding hand hygiene is false?
A HCWs should clean their hands with an antiseptic-containing agent before and after each contact with a patient.
B The use of soap and water for hand washing is required when hands are visibly soiled with blood or body fluids.
C Adherence to hand hygiene guidelines by HCWs is generally poor.
D Alcohol-based hand rubs are inferior to antimicrobial soaps for hand decontamination.
E VRE and MRSA are frequently isolated from the hands of HCWs.
Ref.: 6
Comments
Hand washing by HCWs may be the single most effective measure for preventing nosocomial infection. The spread of bacteria, particularly antibiotic-resistant organisms such as MRSA and VRE, from contaminated HCWs to patients is well documented. Despite recommendations to wash hands before and after all contact with patients, adherence to such policies by HCWs has been poor. Although hand washing with soap and water is required when hands are visibly soiled with blood, the widespread use of alcohol-based hand rubs by HCWs between patient contacts may decrease the spread of resistant bacteria to patients. Alcohol-based products are superior to antimicrobial soaps for standard hand decontamination. Alcohol-based hand rubs have the broadest spectrum of antimicrobial activity among the available hand hygiene products, and their use results in a rapid reduction in microbial skin counts. The ability to make these rubs available at the entrance to patients’ rooms, at the bedside, or in pocket-sized containers to be carried by HCWs may improve compliance with hand hygiene policies. The CDC has recently published guidelines for hand hygiene in heath care settings that include recommendations for hand-washing antisepsis, hand hygiene techniques, and surgical hand antisepsis.
Answer
D
5 Current CDC recommendations concerning HCWs and H1N1 virus include all of the following except:
A All HCWs should be vaccinated for H1N1 virus.
B If H1N1 develops, the HCW must stay out of work for a total of 9 days.
C If H1N1 develops, the HCW must stay out of the hospital for at least 24 hours after fever is no longer present (without fever-reducing medication).
D If in contact with a patient suspected of having H1N1, the HCW should follow standard precautions and wear an N95 respirator.
E All persons coming in and out of the hospital should be screened for flulike symptoms unless they have been vaccinated.
Ref.: 7
Comments
All HCWs should be vaccinated for H1N1. If symptoms of the virus develop, the CDC recommends that the HCW should stay out of work for 7 days from the onset of symptoms or for 24 hours after becoming afebrile without any fever-reducing medication, whichever is shortest. All persons coming in contact with a person suspected or proved to have H1N1 should wear an N95 respiratory mask in addition to following standard precautions. Moreover, it is now recommended that everyone coming in and out of the hospital, including visitors, be screened for flulike symptoms unless they have been vaccinated for H1N1.
Answer
B
6 Contraindication to receiving the attenuated live nasal vaccine for H1N1 virus include all of the following except:
A Age younger than 2 years
B Age 50 years or older
C Pregnancy
D Age younger than 3 years
E Children/adolescents who take aspirin
Ref.: 7
Comments
Currently, the CDC states that the attenuated live H1N1 nasal vaccine is safe for all healthy individuals aged 2 to 49. Contraindications include children 2 years or younger, adults 50 years or older, pregnant patients, and patients with a preexisting medical condition that places them at high risk for complications from influenza (chronic heart or lung disease, diabetes, or kidney failure; illnesses that weaken the immune system; or patients who take medications that can weaken the immune system). The nasal vaccine is also contraindicated in children younger than 5 years with a history of recurrent wheezing, in children or adolescents who take aspirin, in anyone with a history of Guillain-Barré syndrome occurring after receiving influenza vaccine, and in anyone with a severe allergy to eggs.
Answer
D
7 A nonvaccinated surgical resident is exposed to a patient with H1N1, and fevers and upper respiratory symptoms subsequently develop. Which is the correct treatment?
A Amantadine
B Rimantadine
C Fever-reducing medications and supportive care
D Oseltamivir
E None of the above
Ref.: 7
Comments
H1N1 has been shown to be resistant to the adamantane class of drugs (including amantadine and rimantadine) and susceptible to oseltamivir (oral) and zanamivir (nasal). It is recommended that in addition to treating the symptoms and supportive care, persons suspected of having H1N1 should start either oseltamivir or zanamivir therapy. If the symptoms worsen, patients may require hospitalization and more invasive support.
Answer
D
8 Which type of hepatitis virus has a DNA genome?
A Hepatitis A
B Hepatitis B
C Hepatitis C
D All of the above
E None of the above
Ref.: 8
Comments
Five viruses (hepatitis A, B, C, D, and E) are recognized as causes of acute hepatitis. They have some similar and some dissimilar features in how they are transmitted and in the potential consequences of infection. HBV contains partially double-stranded DNA. All the other types are RNA viruses. Hepatitis D (delta hepatitis) is an incomplete virus or virus particle with small, circular RNA. It must coexist with HBV to replicate and produce infection. The diagnosis of hepatic viral infection and determination of disease status depend on the detection of viral proteins encoded by these genomes or the presence of antibodies to them.
Answer
B
9 Worldwide, which of the following is the most common mode of transmission of HCV?
A Fecal-oral
B Sexual
C Parenteral
D Vertical (childbirth)
E Contaminated water
Ref.: 8, 9
Comments
HCV is primarily spread by parenteral routes. Sexual transmission can also occur but is less common than with HBV. Injected drug use currently accounts for most HCV transmission in the United States. Injected drug use leads to transmission of HCV by direct transfer of infected blood on shared needles or syringes and by contamination of drug preparation equipment. Blood transfusions were an important method of spread before the availability of screening. Routine testing of donors for evidence of HCV infection was initiated in 1990, and multiantigen testing was implemented in 1992 and has reduced the risk for infection to 0.001% per unit transfused.
Answer
C
10 What is the prevalence of HCV infection in the United States?
A 0.2%
B 2%
C 5%
D 10%
E 20%
Ref.: 9, 10
Comments
The prevalence of HCV infection in the United States is approximately four times greater than the prevalence of HIV infection. The rate in HCWs, including general, orthopedic, and oral surgeons, is no higher. As would be expected, some populations have a much higher prevalence, including hemophiliacs (60% to 90%), injected drug users (60% to 90%), and chronic hemodialysis patients (up to 60%).
Answer
B
11 The clinical course of the majority of patients with HCV infection is characterized by which one of the following?
A Acute constitutional symptoms and jaundice
B Acute fulminant hepatic failure
C Development of chronic hepatitis
D Progression to cirrhosis
E Development of hepatocellular carcinoma
Ref.: 8, 9
Comments
The incubation period for HCV infection is about 5 to 10 weeks. Most acute infections are asymptomatic, but about 25% of patients may have constitutional symptoms and elevated aminotransferase levels. Fulminant, acute hepatic failure is rare. Infection with HCV is particularly serious, however, because patients with chronic HCV infection can progress to cirrhosis (20%), liver failure (10%), and hepatocellular carcinoma (1% to 5%). Chronic HCV infection may be associated with more severe or progressive liver disease in patients with concurrent hepatopathy, especially alcoholics. Chronic HCV infection is now the leading indication for liver transplantation. In comparison, chronic infection develops in only about 10% of individuals infected with HBV.
Answer
C
12 A surgical resident is stuck with an HCV-contaminated hollow-bore needle. Which of the following tests should be done initially?
A Detection of HCV RNA
B Detection of HCV surface antigen
C Detection of HCV antibodies by enzyme immunoassay
D Measurement of viral load
E Detection of HCV core antigen
Ref.: 9
Comments
The initial screening test for HCV is an antibody immunoassay. The person stuck with the contaminated needle should have baseline testing performed. Since it can take up to 6 months for a person to seroconvert, called the window period, people who have been stuck with a contaminated needle not only require baseline testing but will also need follow-up testing in 6 months.
Answer
C
13 Which of the following blood tests confirm HCV infection?
A Detection of HCV RNA
B Detection of HCV surface antigen
C Detection of HCV antibodies by enzyme immunoassay
D Detection of HCV antibodies and alanine aminotransferase levels of 500 to 1000
E Measurement of HCV viral load
Ref.: 9
Comments
The screening test for HCV is an immunoassay for anti-HCV antibodies. Although the results are positive in 90% of patients infected with HCV, the predictive value of the test is limited when the prevalence of infection is low. In addition, anti-HCV antibodies may not be detectable for up to 18 weeks following exposure. Their presence does not differentiate the state of infection. Qualitative reverse transcriptase polymerase chain reaction (RT-PCR) for detection of HCV RNA is confirmatory. Infection may also be confirmed by recombinant immunoblot assay for HCV antibody.
Answer
A
14 Which of the following is an important risk factor for transmission of HIV to the surgeon after a percutaneous injury?
A The source patient has advanced HIV infection with a CD4+ T-cell count of less than 50 cells/mm3.
B The surgeon sustains a deep puncture injury.
C Blood was visible on the sharp object causing the injury.
D The injury was caused by a device that had entered a blood vessel of the source patient before injury.
E All of the above.
Ref.: 11
Answer
E
Comments
See Question 15.
15 What is the approximate probability of transmission of HCV to an HCW through a needlestick injury from an infected source?
A 0.3%
B 3%
C 5%
D 30%
E 50%
Ref.: 8, 9
Comments
The risk for transmission of HIV after percutaneous exposure to HIV-infected blood is about 0.3%. This risk is influenced by several factors, including depth of the injury and the presence of undiluted blood on the device causing the injury. Exposure to blood from patients in the terminal stages of AIDS, which probably reflects high titers of circulating virus, also increases the risk to HCWs. Although no prospective study demonstrating benefit from postexposure prophylaxis with antiretroviral agents has been completed, a retrospective case-control study suggests that in those who receive zidovudine prophylaxis after exposure, the odds of HIV infection were reduced significantly (by approximately 80%). Postexposure prophylaxis, which now includes at least two antiretroviral agents, should be started immediately (within 72 hours) in HCWs with high-risk injuries.
HCWs are at risk for contracting transmissible viral disease when stuck by needles with contaminated blood or by exposure of mucosal membranes to blood or other body fluids. The risk for documented seroconversion is approximately 3% to 10% for HCV. The risk for HBV infection after needlestick injury is 5% to 30%. The risk of for HCV infection following mucous membrane or other cutaneous exposure has not been defined. The risk for HIV infection with mucous membrane exposure is about 0.1%. When exposure occurs, the infected area should be washed thoroughly with soup and water. The source should be tested for infection with HBV, HCV, and HIV. The risk of contracting HIV infection is greatest with hollow needles, with deep intramuscular injury, or when the exposure involves a greater amount of virus (i.e., from a larger amount of blood or a source with late-stage HIV infection).
Answer
C
16 The operating surgeon is stuck with a needle while performing elective repair of an inguinal hernia. The patient is known to be HIV negative, but his HCV status is unknown. The patient has a known history of intravenous drug abuse. In addition, the operating surgeon is hepatitis B immune because of previous vaccination. Which one of the following measures is appropriate?
A Prophylactic antiviral treatment
B Administration of HCV vaccine and immunoglobulin if the surgeon is HCV antibody negative
C Baseline testing of the surgeon and patient for HCV and follow-up testing of the surgeon at 4 to 6 months
D No testing for the surgeon indicated if the patient tests negative for HCV
E Prophylactic administration of HCV immunoglobulin in addition to baseline testing of both the surgeon and patient and follow-up testing of the surgeon in 4 to 6 months
Ref.: 7, 9
Comments
Anytime that someone is inadvertently stuck with a needle from a patient with unknown HCV status, both the patient and the person stuck should undergo baseline testing for HCV. In addition, the person stuck should have follow-up testing at 4 to 6 months. There is no treatment that has proven efficacy in reducing the risk for seroconversion with HCV; therefore, no prophylaxis for HCV infection is currently indicated.
Answer
C
17 During an emergency appendectomy, a surgical resident sustains an injury from a contaminated hollow-bore needle with spontaneous bleeding. Which one of the following blood-borne organisms is most likely to be transmitted, assuming that the patient was infected with all of them?
A HIV
B HBV
C HCV
D Plasmodium spp. (malaria)
E Treponema pallidum (syphilis)
Ref.: 12
Comments
All the organisms mentioned are potentially transmissible through the exposure described. After significant exposure to blood-borne pathogens, the risk is about 30% for acquiring hepatitis B, 3% for hepatitis C, and 0.3% for HIV disease. Malaria and syphilis may be acquired through blood transfusion, and acquisition through a needlestick is theoretically possible. Because of the high risk associated with hepatitis B exposure, it is recommended that all HCWs be vaccinated against HBV. In the event that a nonimmune HCW is exposed to HBV, it is recommended that the HCW receive hepatitis B immune globulin (HBIG) within 7 days of the exposure and also start a vaccination series. Postexposure prophylaxis with antiretroviral drugs may be indicated after exposure to HIV-infected blood. There is no postexposure prophylaxis available against HCV.
Answer
B
18 A surgical resident sustains a needlestick with a hollow-bore needle contaminated with the blood of a patient who is hepatitis B antigen positive. The resident completed a series of three hepatitis B vaccines 1 year ago, but his antibody response was not checked. Which of the following statements best describes management of this case?
A Observation only is indicated since the source does not have active HBV infection.
B The resident needs a booster of hepatitis B vaccine.
C The resident should receive HBIG immediately.
D The resident should receive HBIG and a hepatitis B vaccine booster immediately.
E The resident needs to be tested for anti–hepatitis B antibody immediately. If the test result is negative, proceed as in alternative D.
Ref.: 13
Comments
HCWs who sustain injuries from needles contaminated with blood containing hepatitis B virus have a risk for the development of serologic evidence of HBV infection as high as 62%. The source patient is hepatitis B antigen positive, which is an indication of active HBV infection. The resident has been vaccinated against HBV, but his immune status is unknown and should be determined. If the resident is anti–hepatitis B antibody positive, no intervention is necessary. However, if anti–hepatitis B antibody negative, HBIG (which can be given up to 7 days after the exposure) and a hepatitis B vaccine booster should be administered. If the resident was never vaccinated, HBIG should be administered immediately and the hepatitis B vaccination series begun.
Answer
E
19 Which of the following clinical conditions is identified by the presence of antibodies in the serum against hepatitis B surface antigen (anti-HBs) in the absence of hepatitis B core antigen (anti-HBc) and hepatitis B surface antigen (HBsAg)?
A The patient is susceptible to HBV infection.
B The patient is immune because of HBV vaccination.
C The patient has an active acute infection with HBV.
D The patient has chronic active hepatitis with HBV.
E The patient has recovered from an HBV infection with subsequent natural immunity.
Ref.: 8, 14
Comments
Testing for hepatitis B surface antigens will be positive in both patients who have been immunized against HBV and those who were previously infected. To distinguish the two clinical situations, one must use other testing. HBsAg positivity indicates an active infection, either acute or chronic. Anti-HBc–positive results indicates that a person either currently has an active infection or has been infected with HBV in the past. If both are negative in the setting of positive anti-HBs, the person has been vaccinated but never infected with HBV.
Answer
B
20 A nonimmune surgical resident is stuck by a contaminated needle from an HBsAg-positive source. Which of the following is the correct initial treatment?
A None because the patient does not have active HBV infection and is immune to HBV
B Interferon
C Vaccination against HBV
D HBIG
E Vaccination against HBV and administration of HBIG
Ref.: 8
Comments
The best method of preventing occupational hepatitis B virus infection is to vaccinate all HVWs at risk if they do not have natural immunity from previous infection. When exposure occurs, the affected area should be immediately and thoroughly washed with soap and water. The source is tested for HBV, HCV, and HIV. If the source tests positive for HBV, nonimmune individuals are given HBIG for passive prophylaxis and are vaccinated. If a previously vaccinated individual incurs a needle injury, titers should be checked and a dose of vaccine given if titers are not detected. Interferon is not used for prophylaxis following acute exposure but may be useful for some patients with chronic HBV or HCV infection.
Answer
E
21 A surgical resident is placing a central venous catheter in a patient who is HIV positive and is stuck with the needle. Which of the following regarding postexposure prophylaxis is true?
A No prophylaxis necessary; however, the surgical resident should have a baseline HIV test performed and follow-up tests in 3 and 6 months.
B The resident should have a baseline HIV test performed and follow-up testing in 3 and 6 months and, in addition, begin combined triple antiretroviral therapy.
C The resident should have a baseline HIV test performed and follow-up testing in 3 and 6 months and, in addition, begin single antiretroviral therapy.
D The resident should have a baseline HIV test performed and follow-up testing in 3 and 6 months and, in addition, begin therapy with two antiretroviral drugs.
E The resident should begin combined triple antiretroviral therapy and have an HIV test performed in 6 months.
Ref.: 7, 9
Comments
Most occupationally acquired human immunodeficiency virus infection has been documented in nurses or laboratory technicians. Postexposure drug prophylaxis should be initiated as soon as possible, ideally within 2 hours. In cases in which the status of the source is unknown, standard serologic testing (enzyme immunoassay and Western blot) is indicated, but the results may take several days. A rapid HIV test can now give results within 1 hour. However, serologic test results may be negative in infected individuals for 3 to 12 weeks following acquisition of the virus. The decision to start postexposure drug prophylaxis must therefore consider any known risk factors that the source may have, regardless of the serologic results. Postexposure prophylaxis consists of multidrug therapy with a combination of nucleoside and protease inhibitors. Adverse side effects are frequent and sometimes severe. Recommendations for postexposure prophylaxis continue to evolve. The most effective method of reducing the risk for transmission of HIV in a person stuck with a needle from a known HIV-positive patient is to begin combined triple antiretroviral therapy. The first dose should be given as soon after exposure as possible. Besides a baseline HIV test, this person should undergo additional follow-up testing at both 3 and 6 months.
Answer
B
22 Which of the following markers is the most clinically useful for monitoring the course of a person infected with HIV?
A Viral load
B CD4+ T-cell count
C Serum neopterin
D Serum oligoclonal immunoglobulins
E Serum p24 antigen level
Ref.: 7, 15
Comments
The CD4+ T-cell count, although somewhat imperfect, is the most useful determination for monitoring the course of an HIV infection. The normal CD4+ count is greater than 600 cells/mm3 with most counts ranging from 800 to 1200 cells/mm3. Symptomatic disease usually begins when the CD4+ count falls below 300 to 400 cells/mm3. Opportunistic infections begin to occur when the CD4+ cell count is less than 200 cells/mm3. The time course of this decline in CD4+ T-cell count is prolonged and may take more than 10 years. Direct quantification of viral load with plasma viremia shows increasing viral titers as the disease progresses. β2-Microglobulin is shed into the serum in HIV-infected patients and reflects increased lymphocyte turnover. Neopterin is produced by macrophages stimulated by interferon. Although both are found in increasing amounts as HIV infection progresses, neither of these two determinations is specific for HIV infection, and they are generally used in a research setting. Determination of p24 antigen is specific for HIV but not very sensitive.
Answer
B
23 The chance of an HIV-infected individual transmitting infection best correlates with which of the following?
A CD4+ T-cell count
B Viral load
C Absolute lymphocyte count less than 1000 cells/mm3
D Active opportunistic infection
E Whether the patient is currently receiving antiretroviral therapy
Ref.: 7, 9, 16
Comments
Blood measurements of viral load reflect the risk for transmission of HIV by any route: parenteral, sexual, or perinatal. The risk of acquiring HIV infection through occupational exposure also correlates with the viral load in the source. Both viral load and the CD4+ count reflect the stage of the disease in that patients with late viral infection have low CD4+ levels and high viral counts. Opportunistic infections are also more prevalent as CD4+ counts fall and immunodeficiency worsens. Clinical acquired immunodeficiency syndrome is defined in patients with positive HIV serologic findings when CD4+ counts are less than 200 cells/mm3 or when one of a number of defined associated conditions exists. The list of these AIDS-defining conditions includes specific opportunistic infections, neoplasms, and degenerative conditions.
Answer
B
24 A 36-year-old man with HIV infection and a CD4+ count of less than 500 cells/mm3 has an incarcerated ventral hernia. In addition to standard precautions, which one of the following is recommended?
A Avoidance of prosthetic mesh
B Broader preoperative prophylactic antibiotic coverage than for a patient who is HIV negative
C Prophylactic trimethoprim/sulfamethoxazole in addition to standard preoperative antibiotics
D Disposable surgical instruments
E None of the above
Ref.: 9
Comments
Beyond the universal precautions that are used for all patients, there are no specific recommendations regarding the preoperative or intraoperative management of patients with human immunodeficiency virus infection. Operative treatment should be performed according to the surgical condition and antiretroviral drug therapy administered according to the status of the HIV disease. Prophylactic antibiotics or prosthetic materials are used for the same indications as for non–HIV-infected individuals. Trimethoprim/sulfamethoxazole is used for the prophylaxis of P. carinii pneumonia in patients with clinical AIDS but has nothing to do with surgical prophylaxis. Standard surgical instruments and sterilization techniques are appropriate. The use of disposable instruments is often convenient and simple when performing minor procedure outside the main operating room.
Answer
E
25 A 28-year-old woman with AIDS has right upper quadrant pain and on ultrasound examination is found to have acute cholecystitis. Which of the following is the appropriate therapy?
A The patient should begin antibiotic therapy but should undergo no surgical intervention because of her immune status.
B The patient should begin antibiotic therapy and have a percutaneous cholecystostomy tube placed.
C The patient should begin antibiotic therapy and undergo open cholecystectomy.
D The patient should begin antibiotic therapy and undergo laparoscopic cholecystectomy.
E None of the above.
Ref.: 17
Comments
AIDS and human immunodeficiency virus infection are not contraindications to laparoscopy. These patients should be managed according to routine general surgery principles. A patient with AIDS and acute cholecystitis should be treated with appropriate antibiotics and laparoscopic cholecystectomy unless the patient is not stable enough or has other comorbid conditions that make surgery too dangerous.
Answer
D
26 The operative mortality rate after laparotomy in patients with AIDS has most closely been associated with which of the following?
A Total lymphocyte count less than 1000 cells/mm2
B CD4+ T-cell count less than 500/mm3
C Active opportunistic infection
D Duration of HIV infection
E Emergency surgery
Ref.: 18
Comments
Prognostic factors in acquired immunodeficiency syndrome patients undergoing abdominal operations have not been extensively analyzed. The cumulative operative mortality rate after major abdominal procedures is approximately 20%. Most deaths are related to the patient’s underlying disease and not to specific operative complications. Emergency operations have been associated with higher mortality rates than have elective procedures, particularly in patients with intestinal perforations because of opportunistic infections such as CMV. However, there is no convincing evidence that patients with HIV infection without AIDS-defining criteria have an inordinate risk for death or complications after abdominal surgery.
Answer
E
27 Laparotomy is performed on a 26-year-old, HIV-positive man who has been hospitalized with abdominal pain, intractable diarrhea, and a perforated viscus. He has a 2-cm cecal perforation, and the colon is dilated throughout. Select the most appropriate therapy.
A Primary repair of the perforation with placement of a drain
B Primary repair of the perforation with a diverting ileostomy
C Ileocecal resection with primary anastomosis
D Ileocecal resection with primary anastomosis and a diverting ileostomy
E Abdominal colectomy with ileostomy and a Hartmann procedure
Ref.: 14, 19
Comments
Infection of the gastrointestinal tract with CMV is one of the most common causes of intestinal perforation in human immunodeficiency virus-infected patients and is an AIDS-defining condition. The diagnosis is based on demonstration of intranuclear inclusion bodies on a biopsy specimen. Initial treatment consists of antiviral agents and support. Surgery is indicated for perforation, bleeding, or obstruction as a result of stricture formation. CMV perforations are most frequently ileocolic in location. They can involve the small intestines, stomach, or duodenum. Operative management of colon perforations is resection without anastomosis. Determination of the extent of resection has various considerations, but since the entire colon is typically involved, total abdominal colectomy is often advisable. Such patients are often desperately ill, and appropriate and timely surgical intervention and aggressive support are necessary for survival.
Answer
E
28 A 30-year-old HIV-positive man undergoes repair of an incarcerated inguinal hernia. His CD4+ T-cell count is 300 cells/mm2. Postoperatively, a wound infection develops at his incision site. Which of the following organisms is most likely responsible?
A CMV
B Staphylococcus
C Candida spp.
D E. coli
E None of the above
Ref.: 9
Comments
Even in a patient with a low CD4+ T-cell count, the most likely source of a wound infection will be from the same flora that affects patients with normal immune systems. In patients undergoing inguinal hernia repair, the most likely cause of a wound infection is Staphylococcus.
Answer
B
29 A 32-year-old, HIV-positive injected drug user is admitted following a seizure. Examination reveals a pronator drift. A CT scan of the head with intravenous contrast material shows two ring-enhancing lesions. Which of the following statements is true?
A Primary CNS lymphoma is the most likely diagnosis.
B Biopsy should be performed on all enhancing lesions in HIV-infected patients.
C Toxoplasmosis is the most likely diagnosis.
D Pyrimethamine is an effective agent for primary prophylaxis of this condition, but it is not very effective for its treatment.
E The neurologic symptoms are unrelated to AIDS.
Ref.: 7, 15, 20
Comments
Ten percent of AIDS patients experience a neurologic symptom as the first sign of their illness, and one or more neurologic deficits eventually develop in 40% of AIDS patients. Major human immunodeficiency virus-related central nervous system diseases include HIV encephalopathy, meningitis, myelopathy, opportunistic infections (PML caused by papovavirus, CMV, herpes, Toxoplasma gondii, and C. neoformans), neoplasms (primary CNS lymphoma), and cerebrovascular complications. T. gondii, the protozoan that causes toxoplasmosis, accounts for 50% to 70% of focal brain lesions in these patients and is the most common cause of focal enhancing lesions on CT. Ten percent to 25% of focal lesions are central nervous system lymphomas. Primary CNS lymphoma is a rare intracranial tumor in the general population, in whom it accounts for only 1.5% of primary brain tumors. However, it is significantly more common in HIV-infected patients, even when compared with other immunosuppressed populations. Current management recommendations for HIV-infected patients with focal brain lesions include 2 to 3 weeks of empirical treatment of toxoplasmosis, followed by biopsy if the radiologic or clinical condition deteriorates.
Answer
B
30 Select the true statement regarding splenectomy in HIV-infected patients.
A The laparoscopic approach is contraindicated.
B HIV-associated thrombocytopenia is the primary indication.
C It is associated with a 30% risk for overwhelming postsplenectomy infection.
D Splenectomy may accelerate progression to AIDS.
E All of the above.
Ref.: 9, 14, 21
Comments
Thrombocytopenia similar to but immunologically distinct from classic idiopathic thrombocytopenic purpura develops in approximately 10% to 20% of patients with asymptomatic human immunodeficiency virus disease. Initial treatment with corticosteroids produces a response in most (80%) patients. Those who fail to respond or who relapse when steroid use is tapered are appropriate candidates for splenectomy. Splenectomy yields a favorable result in 80% of patients. Neither the morbidity of splenectomy nor the risk for overwhelming postsplenectomy infection appears to be increased in HIV-infected patients. Likewise, there is no evidence that absence of the spleen worsens HIV disease. In fact, it has been suggested that splenectomy may actually slow disease progression in some patients. Other occasional indications for splenectomy in HIV-related conditions include opportunistic infections, abscesses, and malignancies.
Answer
B
31 A 60-year-old immigrant from China is admitted to the hospital with fevers and a cough productive of bloody sputum. A chest radiograph demonstrates a right upper lobe infiltrate. The patient’s TB exposure is unknown. Which of the following precautions is appropriate?
A No precautions are necessary.
B The patient should be admitted to a shared room but be required to wear a mask.
C The patient should be admitted to a private room but does not need a mask during transport.
D The patient should be admitted to a private room and should wear a mask during transport.
E The patient should be admitted to a negative pressure private room and wear a mask during transport.
Ref.: 7
Comments
Airborne precautions are necessary to reduce the exposure of staff and other patients to individuals with suspected pulmonary or laryngeal tuberculosis. Early recognition of patients at risk for TB is critical, including patients with possible symptoms of TB and those at higher risk for active disease. Typical symptoms include persistent cough, bloody sputum, fever, night sweats, and weight loss. A chest radiograph may show a cavitary lesion or upper lobe infiltrate. Individuals at higher risk include the homeless, elderly, known contacts of TB cases, injected drug users, foreign-born individuals, and patients with HIV infection, renal failure, malignancy, or immunosuppression. The largest growing proportion of new TB cases is in the HIV-infected and immunosuppressed population. Persons with suspected TB must have their face covered with a surgical mask during transport and should be admitted to a private negative airflow room equipped with engineering controls specifically designed to reduce airborne exposure. Precautions must be implemented promptly for any suspected case and should not be delayed to wait for confirmation by acid-fast bacillus (AFB) culture results, which may take weeks. Staff entering the patient’s room must wear special particulate filter respirators (fit testing required) or equivalent respirator systems. Use of appropriate respiratory equipment for protection of HCWs is mandated by the Occupational Safety and Health Administration (OSHA) and the National Institute of Occupational Safety and Health (NIOSH).
Answer
E
32 The patient described in Question 31 is scheduled for bronchoscopy. Which of the following statements is correct?
A The endoscopy staff should wear a powered air-purifying respirator (PAPR) during bronchoscopy.
B The endoscopy staff should take prophylactic INH for 3 days after the procedure.
C Bronchoscopy should be performed with the patient under general anesthesia and the use of endotracheal intubation.
D Bronchoscopy should be deferred if the patient’s tuberculin skin test result is positive.
E Bronchoscopy is contraindicated until the result of the PPD test is available.
Ref.: 1
Comments
Health care providers are at increased risk for exposure to tuberculosis during cough-inducing or aerosolizing procedures, such as bronchoscopy, endotracheal intubation, or suctioning. Respiratory protection requires use of a particulate filter respirator or a PAPR. The latter device provides filtered air to a hood that is worn. Use of a PAPR may be recommended when prolonged exposure is possible, such as during bronchoscopy. The risk for infection depends on the concentration of droplet nuclei and the duration of exposure. The diagnosis of pulmonary TB is made presumptively on the basis of the tuberculin skin test and chest radiograph results and confirmed by AFB smear and culture results. Bronchoscopy is indicated for the diagnosis of patients with undiagnosed pulmonary infection and for the exclusion of cancer, regardless of the skin test results.
Answer
A
33 A surgical resident performs endotracheal intubation of a patient. The patient is unknown to the resident, and the resident had not worn a mask during intubation. Subsequently, the resident is informed that the patient has active TB. The resident has had previous negative PPD tests. The appropriate measure for the resident is:
A No intervention is necessary.
B The resident should have a PPD test performed and prophylactic INH started regardless of the result.
C The resident should have a PPD test performed and prophylactic INH started only if the result is positive and the resident does not have symptoms of active infection.
D The resident should have a PPD test performed and INH started only if the result is positive and symptoms develop in the resident.
E The resident does not need a PPD test but should have chest radiography performed.
Ref.: 7
Comments
Exposure to M. tuberculosis is determined by skin testing. If there is any concern for exposure to active disease, especially in a high-risk situation such as intubation in which the resident is directly exposed to respiratory secretions, the patient should have a PPD test performed. If the PPD results are positive, the resident should begin treatment with INH. A chest radiograph should not be performed in place of the PPD test. If symptoms develop, a chest radiograph is warranted. Infection develop in less than 10% of exposed individuals. Skin testing is performed at least annually in HCWs. The majority of PPD-positive individuals have old exposures. When PPD test results are positive, however, a chest radiograph and sputum for AFB smear and culture are obtained. Isoniazid prophylaxis is indicated for persons younger than 35 years with positive skin test results and those older than 35 years with high-risk conditions (i.e., HIV infection, injected drug use, contact with a known TB source, from a medically underserved population, foreign born, or those with abnormal chest radiograph results). The duration of prophylaxis is 6 to 12 months. Active pulmonary TB is diagnosed by sputum AFB smear or culture analysis (or both). The standard treatment of active disease involves a multidrug regimen with INH, RIF, and other drugs (pyrazinamide, ethambutol, or streptomycin) for months. Surgical therapy (usually resection) is occasionally necessary for patients who fail medical therapy or for those in whom persistent problems develop, such as a residual lung cavity or destruction, bronchiectasis, or hemoptysis.
Answer
C
34 A 60-year-old woman with a history of multiple soft tissue abscesses has a recurrent abscess on her right thigh. This patient had a recent hospitalization for exacerbation of congestive heart failure, during which she was in the hospital for 5 days. Because of her history of previous MRSA abscesses, vancomycin therapy is started. On morning rounds all of the following precautions should be taken except:
A Washing hands before examining the patient
B Wearing gloves while examining the patient
C Wearing a mask while examining the patient
D Wearing a gown while examining the patient
E Washing hands after examining the patient
Ref.: 1
Comments
Contact precautions are indicated in this patient and include washing one’s hands both before and after leaving the patient’s room and donning both a gown and gloves while in the patient’s room. Wearing a mask is not indicated for patients who are on contact precautions.
Answer
C
35 An 80-year-old woman who lives in a nursing home and who had just finished a 10-day course of antibiotics has abdominal pain and profuse diarrhea. Her stool is tested and comes back positive for C. difficile. What is the most appropriate initial management?
A Oral vancomycin
B Intravenous vancomycin
C Metronidazole
D Vancomycin enemas
E Supportive treatment only
Ref.: 14
Comments
The most appropriate initial treatment of C. difficile colitis is metronidazole. If the patient is not improving, it is appropriate to try oral vancomycin. In refractory severe cases it is also appropriate to use vancomycin enemas.
Answer
C
36 All of the following precautions are appropriate for the patient in Question 35 except:
A The physician should wear both gloves and a gown when examining the patient.
B If possible, there should be a disposable stethoscope dedicated to that patient in the room.
C The patient should be placed in a private room.
D All visitors should wear gloves, a gown, and a mask.
E Hands should be washed before entering and after leaving the patient’s room.
Ref.: 1, 14
Comments
This patient is on contact precautions because of C. difficile colitis since it is spread by direct contact. Appropriate precautions include donning a gown and gloves and washing hands both before entering and after leaving the patient’s room. There is no indication for anyone to wear a mask in this patient’s room. In addition, the patient should be placed in a private room. It is also ideal to have a disposable stethoscope dedicated to that patient to avoid spreading C. difficile. If not available, the stethoscope must be cleaned after use.
Answer
D
References
1 Centers for Disease Control and Prevention (CDC). Healthcare-associated infections (HAIs). Available at www.cdc.gov/hai
2 Garner JS. Guidelines for isolation precautions in hospitals. The Hospital Infection Control Practices Advisory Committee. Infect Control Hosp Epidemiol. 1996;17:53-80.
3 Perl TM, Cullen JJ, Wenzel RP, et al. Intranasal mupirocin to prevent postoperative Staphylococcus aureus infections. N Engl J Med. 2002;346:1871-1877.
4 Salgado CD, Farr BM, Calfee DP. Community-acquired methicillin-resistant Staphylococcus aureus: a meta-analysis of prevalence and risk factors. Clin Infect Dis. 2003;36:131-139.
5 Centers for Disease Control and Prevention (CDC). Vancomycin-resistant Staphylococcus aureus—Pennsylvania, 2002. MMWR Morb Mortal Wkly Rep. 2002;51:902.
6 Boyce JM, Pittet D. Guidelines for hand hygiene in healthcare settings: recommendations of the Healthcare Infection Control Practices Advisory Committee and the HICPAC/SHEA/APIC/IDSA Hand Task Force. Society for Healthcare Epidemiology of America Association for Professionals in Infection Control/Infectious Diseases Society of America. MMWR Recomm Rep. 2002;51(RR-16):1-45.
7 Centers for Disease Control and Prevention website www.cdc.gov.
8 Dellinger EP. Surgical infections. In Mulholland MW, Lillemoe KD, Doherty GM, editors: Greenfield’s surgery: scientific principles and practice, ed 4, Philadelphia: Lippincott Williams & Wilkins, 2006.
9 Bartlett JG. Occupational exposure to HIV and other blood-borne pathogens. In Cameron JL, editor: Current surgical therapy, ed 9, Philadelphia: CV Mosby, 2008.
10 Recommendations for prevention and control of hepatitis C (HCV) virus and HCV-related chronic disease. Centers for Disease Control and Prevention. MMWR Recomm Rep. 1998;47(RR-19):1-39.
11 Dolin R, Masur H, Saag MS. AIDS therapy, ed 2. Philadelphia: Churchill Livingstone; 2003.
12 Mandell GL, Bennett JE, Dolin R. Principles and practice of infectious diseases, ed 5. Philadelphia: Churchill Livingstone; 2000.
13 U.S. Public Health Service. Updated U.S. Public Health Service guidelines for the management of occupational exposures to HBV, HCV, and HIV and recommendations for postexposure prophylaxis. MMWR Recomm Rep. 2001;50(RR-11):1-52.
14 Anaya DA, Dellinger EP. Surgical infections and choice antibiotics. In Townsend CM, Beauchamp RD, Evers BM, et al, editors: Sabiston textbook of surgery: the biological basis of modern surgical practice, ed 18, Philadelphia: WB Saunders, 2008.
15 Public Health Service guidelines for the management of health care worker exposures to HIV and recommendations for postexposure prophylaxis. Centers for Disease Control and Prevention. MMWR Recomm Rep. 1998;47(RR-7):1-33.
16 1993 Revised classification system for HIV infection and expanded surveillance case definition for AIDS among adolescents and adults. MMWR Recomm Rep. 1992;41(RR-17):1-19.
17 HIV InSite website by the University of California San Francisco, Section of Surgery in Patients with HIV http://hivinsite.ucsf.edu
18 Deziel DJ, Hyser MJ, Doolas A, et al. Major abdominal operations in acquired immunodeficiency syndrome. Am Surg. 1990;56:445-450.
19 Beck DE, Wexner SD. Fundamentals of anorectal surgery. New York: McGraw-Hill; 1992.
20 . HIV InSite website by the University of California San Francisco, Section of Toxoplasmosis and HIV. Available at http://hivinsite.ucsf.edu
21 Tsoukas CM, Bernard NF, Abrahamowicz M, et al. Effect of splenectomy on slowing human immunodeficiency virus disease progression. Arch Surg. 1998;133:25-31.