Escherichia coli O157: H7 Diarrhea in the United States: Clinical and Epidemiologic Features

doi:10.1059/0003-4819-126-7-199704010-00002

Escherichia coli O157: H7 Diarrhea in the United States: Clinical and Epidemiologic Features

for the Escherichia coli O157:H7 Study Group. Acknowledgments: The authors thank Elizabeth Astagneau, MD, and Alexander Rowe, MD, for help with data management; the National Foundation for Infectious Diseases for administrative support; Pro-Lab, Inc. (Round Rock, Texas) for provision of E. coli O157 latex reagents; DiMed Corp. (St. Paul, Minnesota) for supplying sorbitol-MacConkey culture media; Daniel Cameron and Evangeline Sowers for laboratory assistance; and Robert V. Tauxe, MD, for helpful comments. Grant Support: In part by the Committee on Food Microbiology of the International Life Sciences Institute-Nutrition Foundation. Requests for Reprints: Laurence Slutsker, MD, MPH, Foodborne and Diarrheal Diseases Branch, Mailstop A-38, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30333. Current Author Addresses: Drs. Slutsker, Ries, and Griffin, Ms. Greene, and Ms. Wells: Foodborne and Diarrheal Diseases Branch, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30333.

Abstract

Background: Escherichia coli O157:H7 is increasingly recognized as a cause of bacterial diarrhea in the United States, but the frequency of its isolation and the clinical and epidemiologic features of E. coli O157:H7 infection in a large, geographically diverse population of patients have not been well described.

Objective: To determine the frequency 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 pathogen identification.

Measurements: Clinical, epidemiologic, and laboratory information was collected for infected and uninfected patients. Isolates of E. coli O157:H7 were tested for production of Shiga toxin. Patient charts were then reviewed.

Results: Escherichia coli O157:H7 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 96.0]) and was the pathogen most commonly isolated from visibly bloody stool specimens that yielded a bacterial enteric pathogen (39% of such specimens). The highest age-specific isolation proportions from fecal specimens for E. coli O157:H7 were in patients 5 to 9 years of age (0.90%) and 50 to 59 years of age (0.89%). Clinical features independently associated with E. coli O157:H7 infection compared with the other enteric pathogens included a history of bloody diarrhea (OR, 18.6 [CI, 7.4 to 48.6]), visibly bloody stool specimens (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 × 10⁹/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 groups, isolation proportions from fecal specimens for E. coli O157:H7 surpassed those of other common enteric pathogens. One third of isolates of this organism came from nonbloody specimens. Because person-to-person transmission of E. coli O157:H7 is not uncommon and infection with this organism may cause severe disease, stool specimens from all patients with a history of acute bloody diarrhea should be cultured for E. coli O157:H7.