ESCHERICHIA-COLI O157-H7 DIARRHEA IN THE UNITED-STATES - CLINICAL ANDEPIDEMIOLOGIC FEATURES

Background: Escherichia coli O157:H7 is increasingly recognized as a c ause of bacterial diarrhea in the United States, but the frequency of its isolation and the clinical and epidemiologic features of E. coli O 157:H7 infection in a large, geographically diverse population of pati ents have not been well described. Objective: To determine the frequen cy of isolation of E. coli O157:H7 relative to that of other bacterial enteric pathogens in a nationwide sample of patients and to identify the clinical and epidemiologic features of E. coli O157:H7 infection. Design: Population prevalence study from October 1990 to October 1992. Setting: 10 U.S. hospitals. Patients: Both inpatients and outpatients who had stool samples submitted to 1 of 10 laboratories for routine p athogen identification. Measurements: Clinical, epidemiologic, and lab oratory information was collected for infected and uninfected patients . Isolates of E. coli O157:H7 were tested for production of Shiga toxi n. Patient charts were then reviewed. Results: Escherichia coli O157:H 7 was isolated from 118 (0.39%) of the 30 463 fecal specimens tested. The proportion of fecal specimens with isolates was higher at northern sites (0.57%) than at southern sites (0.13%) (P < 0.001). Escherichia coli O157:H7 was more likely to be isolated from visibly bloody stool specimens than from specimens without visible blood (odds ratio [OR], 59.2 [95% CI, 36.6 to 96.01]) and was the pathogen most commonly isol ated from visibly bloody stool specimens that yielded a bacterial ente ric pathogen (39% of such specimens). The highest age-specific isolati on proportions from fecal specimens for E. coli O157:H7 were in patien ts 5 to 9 years of age (0.90%) and 50 to 59 years of age (0.89%). Clin ical features independently associated with E. coli O157:H7 infection com pared with the other enteric pathogens included a history of blood y diarrhea (OR, 18.6 [CI, 7.4 to 48.6]), visibly bloody stool specimen s (OR, 8.1 [CI, 3.6 to 18.3]), no reported fever (OR, 8.3 [CI, 1.6 to 50.0]), leukocyte count greater than 10 x 10(9)/L(OR, 4.0 [CI, 1.7 to 9.5]), and abdominal tenderness on physical examination (OR, 2.9 [CI, 1.2 to 7.2]). Conclusions: In some geographic areas and some age group s, isolation proportions from fecal specimens for E. coli O157:H7 surp assed those of other common enteric pathogens. One third of isolates o f this organism came from nonbloody specimens. Because person-to-perso n transmission of E. coli O157:H7 is not uncommon and infection with t his organism may cause severe disease, stool specimens from all patien ts with a history of acute bloody diarrhea should be cultured for E. c oli O157:H7.