Setting: ED
CC: “My leg is red and swollen.”
VS: BP: 134/88 mm Hg; P: 96 beats/minute; T: 102°F; R: 18 breaths/minute
HPI: A 49-year-old generally healthy man with several days of increasing redness and warmth of his right lower extremity presents at the ED. The leg is painful. He has been “feeling warm” for a few days as well. He denies injury to the leg, cancer, long flights, knee surgery, or immobility. He has had no previous episode of skin infection and no recent hospitalizations.
PMHX: none
Medications: none
PE:
General: well-groomed, alert, and friendly
Extremities: right leg has an area of redness in the skin over the medial half of the lower leg and the calf (Figure 10-4). Redness is warm to touch. There are no ulcerations. Tinea pedis is found in between the toes.
CCS allows the artificial distinction between choosing tests or treatments to disappear. In this respect, CCS is similar to real life. This patient needs several things simultaneously, and it would be artificial to ask a student to choose only one of them.
Initial Orders:
Cefazolin IV
Lower-extremity duplex US
Blood cultures
Figure 10-4. Cellulitis in an older man with venous stasis dermatitis. (Reproduced with permission from Richard P. Usatine, MD.)
Cellulitis Organisms
Number 1 is S. aureus.
Number 2 is beta-hemolytic streptococci.
Sensitive and resistant S. aureus cannot be distinguished by appearance.
Exclude clot in all leg-related cellulitis.
Beta-Hemolysis = Complete Hemolysis
Which of these are considered “standard” in this patient with cellulitis?
a. Potassium hydroxide (KOH) prep of interdigital web space
b. Biopsy of skin
c. Infuse sterile saline into skin and aspirate for culture
d. X-ray of leg
e. Swab surface
Answer a. Potassium hydroxide (KOH) prep of interdigital web space
Skin breakdown and tinea pedis was seen on examination. You should always look for an entry point of skin breakdown in people who have cellulitis. Healthy skin should not develop cellulitis. You also need to correct any point of entry or the infection will recur. Biopsy of skin is virtually never done. Patients are treated empirically with antistaphylococcal and streptococcal antibiotics such as cefazolin, nafcillin, or oxacillin for sensitive organisms. If there is methicillin-resistant Staphylococcus aureus (MRSA) suspected, use vancomycin, linezolid, ceftaroline, or daptomycin.
Move the clock forward to obtain the results of the duplex US of the leg and the KOH prep.
Leg duplex US is >95% sensitive and specific for deep venous thrombosis (DVT).
Reports:
Lower extremity duplex US: negative, no clot
KOH: fungal hyphae visible
Fungi do not dissolve in KOH.
Chitin are
• In the fungal cell wall
• Not dissolvable by KOH
• Same as lobster or crab shell
Ceftaroline is the only cephalosporin to cover MRSA.
Orders:
Apply terbinafine topically to feet.
Continue cefazolin.
Cellulitis and tinea pedis do not have a clear length of therapy that you can determine in advance. Move the clock forward a day at a time and see if there is improvement in the temperature and examination. Most patients should markedly improve in 2 to 3 days and be discharged.
Oral MRSA Drugs
• Doxycycline
• Trimethoprim-sulfamethoxazole (TMP-SMZ)
• Clindamycin
Move the clock forward 1 day to reassess the patient’s temperature and examination. Because we rarely ever aspirate and culture out a specific organism for cellulitis, we are stuck treating empirically and looking for a response in 24 to 48 hours.
Antibiotics needs at least 12 to 24 hours even to begin to work.
Interval History: “Feet are less itchy. Leg is less painful.”
PE:
T: 100.6°F
Extremities: less red and warm
Molds such as Epidermophyton and Trichophyton cause tinea pedis. What is the major difference between molds and yeast?
a. Response to topical nystatin
b. Formation of spores at room temperature
c. Causing human disease
d. Nothing
Answer b. Formation of spores at room temperature
Both molds and yeast are fungi. Yeasts are organisms like Candida. Candida only grows at body temperature (98.6°F or 37°C). Yeasts do not form spores at room temperature. Molds are organisms that cause skin or nail infections. Also like Aspergillus, blastomycosis, and coccidioidomycosis, they form spores at room temperature that can exist at temperatures much colder than room temperature for an indefinite period of time. That is why you can inhale mold spores in the environment, but cannot obtain yeast growth such as Candida in the same way.
When improved, a patient with cellulitis can be sent home on an oral version of the medication used intravenously in the hospital. This is easy for cefazolin. The oral equivalent of cefazolin is cephalexin. It is essentially identical to cefazolin. Treatment with oral equivalents of antistaphylococcal medication against resistant organisms, such as MRSA, is much more difficult. There is no direct oral equivalent of vancomycin.
Oral vancomycin is not absorbed.
Orders:
Stop cefazolin.
Transfer the patient to home.
Schedule a follow-up office appointment in 7 days.
Continue topical terbinafine (or clotrimazole or nystatin).
Give oral cephalexin.
Treatment of cellulitis is empiric.
No specific organism is identified.
Look for response to treatment, and switch if there is none.