Escherichia coli O157: H7 Infection in Humans

OBJECTIVE: To review the clinical relevance of Escherichia coli O157:H7 infection, including the epidemiology of the infection and its clinical presentations, pathogenesis, microbiology, diagnosis, treatment, and prevention. DATA SOURCES: Articles on E. coli O157:H7 were identified through MEDLINE and the bibliographies of relevant articles. STUDY SELECTION: All articles and case reports describing E. coli O157:H7 and its infection were selected. DATA EXTRACTION: The data were abstracted without judgments about study design. Data quality and validity were assessed by independent author reviews. DATA SYNTHESIS: Infection with E. coli O157:H7 presents with a wide spectrum of clinical manifestations, including asymptomatic carriage, nonbloody diarrhea, hemorrhagic colitis, the hemolytic-uremic syndrome, and thrombotic thrombocytopenic purpura. Not only is E. coli O157:H7 an important agent for hemorrhagic colitis, it is also one of the leading causes of bacterial diarrhea. Patients at extremes of age have an increased risk for infection and associated complications. Transmission of E. coli O157:H7 is primarily food-borne. Undercooked meat is the most common culprit, and secondary person-to-person spread is also important. The organism produces at least two Shiga-like toxins that differ antigenically, physicochemically, immunologically, and in their biological effects. These toxins are thought to have direct pathogenic significance in E. coli O157:H7 infection. This infection is usually diagnosed from a positive stool culture, from the presence of Shiga-like toxins, or both. Timely collection (within 7 days of illness onset) of a stool sample for culture is imperative for a high recovery rate. Treatment is primarily supportive and includes the management of complications as necessary. Antibiotic therapy has not been proved beneficial. Important public health measures include educating the public on the danger of eating undercooked meat, increasing physician awareness of E. coli O157:H7 infection, and mandating case reporting. CONCLUSIONS: Infection with E. coli O157:H7 presents with many clinical manifestations and should be included in the differential diagnosis for any patient with new-onset bloody diarrhea. Development of the hemolytic-uremic syndrome or thrombotic thrombocytopenic purpura should raise strong suspicion of E. coli O157:H7 infection and should lead to prompt evaluation. If infection is confirmed, it should be reported to public health officials.