Diarrhea from E. coli
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What is E. coli?
E. coli (Escherichia coli) is a bacterium that normally lives in the intestines of humans and animals. Although most E. coli strains re harmless, several are known to produce toxins that cause diarrhea. The classifications of diarrhea-causing E. coli are:
- Enterotoxigenic E. coli (ETEC)
- Enteroinvasive E. coli (EIEC)
- Enteropathogenic E. coli (EPEC)
- Enterohemorrhagic E. coli (EHEC)
- Enteroaggregative E. coli (EAEC)
What are the symptoms of E. coli infection?
ETEC is the most common cause of Traveler's diarrhea. EPEC manifests as severe and protracted diarrhea in neonates and infants. EIEC manifests as bloody mucoid diarrhea with fever, crampy abdominal pain and tenesmus. EHEC manifests as bloody diarrhea with low or no fever at all. Ten per cent of patients with EHEC develop Hemolytic Uremic Syndrome (HUS), most commonly caused by the serotype 0157:H7, characterized by a triad of acute renal failure, hemolytic anemia and thrombocytopenia. Mortality for EHEC is approximately 5%. Except for EIEC and EHEC, the rest of the strains do not cause systemic infection or complication.
How is E. coli infection transmitted?
The route of infection of diarrhea-causing E. coli is fecal-oral. This can be transmitted through contaminated food and water. Person-to-person transmission can occur if infected people do not wash their hands after using the toilet or changing diapers. E. coli 0157:H7 is transmitted by ingestion of beef and other foods contaminated with cattle feces. E. coli is killed by thorough cooking.
How is E. coli diarrhea diagnosed by laboratory methods?
Diarrhea-associated E. coli is difficult to differentiate in most clinical microbiology laboratories from E. coli normally present in the stool. Serotyping with commercially available antisera is needed to identify the different types of E. coli. Most diagnostic laboratories do not perform these studies routinely. For suspected EHEC, stool should be cultured for E. coli 0157:H7 as early as possible during the illness.
How is E. coli diarrhea treated?
In all age groups, the cornerstone of treatment of E. coli diarrhea is replacement of fluids and electrolytes. The disease is self-limited to a week or less in most patients. Practically speaking, in most instances, the clinician is left to make therapeutic decisions without knowing the etiologic agent responsible since routine diagnostic microbiology cannot differentiate pathogenic ones from harmless ones. Empiric antimicrobial therapy is justifiable for immunocompromised hosts, for patients with prolonged or severe illness or a history of significant risk factor (specific food ingestion, travel, exposure to known contacts, etc.) and for cases of inflammatory or dysenteric illness. Treatment of EHEC is mainly supportive. Antibiotic treatment of EHEC is still controversial but generally is not recommended. There is a significantly increased risk of HUS in patients with E. coli 0157:H7 treated with antibiotics.
How can E. coli infections be prevented?
Good hygienic practices in all instances are a must. Avoidance of raw, unpeeled vegetables, tap water and ice while traveling is important. Antimicrobial prophylaxis is not recommended. Meticulous hand washing and appropriate disposal of soiled diapers are necessary. Beef products should be thoroughly cooked before ingestion. Cross contamination may be minimized by washing hands and surfaces after contact with raw ground beef, storing raw beef to ensure that drippings do not contaminate other foods and using different utensils to handle raw and cooked meat. Unpasteurized milk and dairy products and juices should not be consumed. For infants, breastfeeding should be encouraged since breastmilk has protective effect against E. coli. There are no available vaccines for it.
Excerpt from Health Alert, a bulletin from the Infection Control Service, St. Luke's Medical Center.