David M. Cline
EPIDEMIOLOGY
Foodborne disease is an illness that occurs in two or more people after the consumption of common food source. Contamination can come from bacteria, viruses, or protozoans.
Viruses are the most common source, including Norwalk-type (58% overall, United States), astrovirus, rotaviruses, and enteric adenoviruses.
Bacterial sources include nontyphoidal Salmonella (11% overall, most common cause for hospitaliza-tion and associated death in the United States), Clostridiumperfringens, Campylobacter spp., Listeria monocytogenes, Shigellaspp., Shiga toxin-producing Escherichia coli (STEC), and Staphylococcus aureus.
Parasitic causes include Giardia lamblia, Toxoplasma gondii, Entamoeba histolytica, and Cryptosporidium.
The most common associated foods are poultry, leafy vegetables, and fruits/nuts.
In addition, after eating reef fish that feed on certain dinoflagellates (algae), patients may experience scombroid or ciguatera poisoning, which is a toxin-induced syndrome.
Waterborne diseases occur from ingestion of or contact with contaminated water from swimming pools, hot tubs, spas, or naturally occurring fresh or salt water.
Symptoms of waterborne diseases can be either GI or dermatologic. Common organisms include the majority of those associated with foodborne illness plus Vibrio species, Aeromonas species, Pseudomonas aeruginosa, Yersiniaspecies, hepatitis A, nontuber-culous Mycobacterium, and less frequent organisms.
PATHOPHYSIOLOGY
Foodborne pathogens are responsible for >200 known diseases and can cause illnesses through a variety of mechanisms.
Some pathogens, such as S. aureus, Bacillus cereus, and Clostridium botulinum (botulism), produce toxins capable of causing illness.
Preformed toxins are present in the food before ingestion and result in the rapid onset (1–6 hours) of vomiting.
Other pathogens, such as Vibrio, Shigella, and STEC, produce toxins after ingestion, causing diarrhea and lower GI symptoms (cramping and sometimes bloody diarrhea) with onset at approximately 24 hours.
Some of the most common pathogens, such as the enteric viruses, Salmonella, Campylobacter, and Shigella, directly invade the intestinal epithelial barrier. These pathogens often cause systemic symptoms such as fever and upper and lower GI symptoms lasting from 24 hours to weeks.
Alteration of the gastrointestinal tract’s protective mechanisms by medications, chronic systemic diseases, surgery, age, or the pathogen itself can increase susceptibility to foodborne disease.
Proton pump inhibitors, histamine-2 (H2) blockers, and antacids reduce gastric pH.
Recent antibiotic use, chemo- or radiation therapy, and recent surgery alter the intestinal flora.
Decreased intestinal motility from narcotics, antiperi-staltic drugs, and surgery may encourage pathogen growth and migration.
CLINICAL FEATURES
Symptoms of both foodborne and waterborne illness include vomiting, diarrhea, abdominal cramping, fever, dehydration, malaise, and in some, bloody stool.
Physical examination may be remarkable for features of dehydration, and in some, stool positive for frank or occult blood.
Prolonged illness beyond 2 weeks suggests protozoan parasites.
STEC may be complicated by hemolytic uremic syndrome (decreased urine output, symptoms of anemia), especially after antibiotic treatment. STEC classically presents with vomiting, moderate to marked stomach cramps, diarrhea (often bloody), and mild fever, not over 101°F/38.5°C.
Patients with scombroid fish poisoning or ciguatera poisoning have symptoms similar to foodborne illness described immediately above, 1 to 24 hours after ingestion of reef fish. In addition, patients with scombroid poisoning frequently have flushing and headache due to histamine reaction.
Those with ciguatera poisoning may have headaches, muscle aches, paresthesias, or a burning sensation on contact with cold, due to sodium channel-mediated nerve depolarizations.
Neurologic symptoms may be prolonged beyond the ED visit.
The skin manifestations of waterborne illness vary from simple cellulitis, the painful indurated plaque of Mycobacterium marinum, to necrotizing infections, which may include hemorrhagic bulla with Vibrio vulnificus.
Patients with Aeromonas hydrophila skin infections often have a history of trauma associated with freshwater exposure, and may have foul-smelling wounds.
DIAGNOSIS AND DIFFERENTIAL
Bedside testing for fecal occult blood is the most commonly indicated test; otherwise most patients need no laboratory testing, unless significantly dehydrated or other significant diagnoses are being considered.
For those more acutely ill, consider fecal leukocytes, the neurophil marker lactoferrin, electrolytes, and complete blood count.
Stool Gram stain may reveal Campylobacter. Stool cultures are more likely to be positive in those with positive fecal leukocytes or lactoferrin.
STEC and Vibrio cultures require specific procedures (check local laboratory guidelines).
Reserve ova and parasite testing for those patients with chronic symptoms, immunocompromised, or patients with a confirmed source of parasite.
Other considerations include Rotavirus antigen testing in children from daycare settings, daycare workers, or older adults.
Clostridium difficile antigen testing may be indicated in those with prolonged symptoms, recent antibiotic use, significant comorbidities, or extremes of age.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Most cases are self-limited and improve with nonspecific treatment.
Initiate oral rehydration fluids initially if tolerated. Intravenous rehydration with normal saline will benefit those significantly dehydrated, or those with continued vomiting.
Antiemetics, such as metoclopramide 10 milligrams PO or IV, or ondansetron 4 milligrams PO or IV may facilitate oral rehydration.
Antihistamines, such as diphenhydramine 25 milligrams PO or IV, may improve the symptoms of scombroid fish poisoning.
Loperamide 4 milligrams initially and then 2 milligrams after every unformed stool up to a maximum of 16 milligrams/d is indicated in mild to moderate, non-bloody diarrhea in adults without fever (do not use in patients with STEC).
Antibiotics are favored only in those patients with an increasing number of the following features: significant abdominal pain, bloody diarrhea, fever over 101°F/38.5°C, symptom duration >48 hours, impaired host, positive fecal leukocytes, or lactoferrin; however, antibiotics are contraindicated in patients with STEC.
When treatment is indicated, recommended agents include ciprofloxacin 500 milligrams PO twice per day, or trimethoprim-sulfamethoxazole double-strength twice daily, for 3 to 5 days.
Organism-specific antibiotic recommendations can be found in the parent text cited at the end of this chapter.
Vibrio vulnificus skin infections are treated with doxycycline 100 milligrams IV or PO twice daily, plus ceftazidime 2 grams IV every 8 hours.
Aeromonas skin infections are treated with ciprofloxacin 500 milligrams twice daily (mild cases) or with piperacillin-tazobactam 3.375 grams IV every 6 hours in severe cases.
Necrotizing infections require emergent surgical debridement.
Most patients can be treated as outpatients, and admission is indicated in those appearing toxic, those in whom vomiting cannot be controlled, the immunocompromised, or those at the extremes of age with significant symptoms.
For further reading in Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7th ed., see Chapter 154, “Foodborne and Waterborne Diseases,” by Patrick L. McGauly and Simon A. Mahler.