Escherichia coli O157:H7 diarrhea in the United States: clinical and epidemiologic features

Ann Intern Med. 1997 Apr 1;126(7):505-13. doi: 10.7326/0003-4819-126-7-199704010-00002.


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 30463 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 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 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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Campylobacter Infections / diagnosis
  • Campylobacter Infections / epidemiology
  • Child
  • Diarrhea / diagnosis
  • Diarrhea / epidemiology*
  • Diarrhea / microbiology
  • Dysentery, Bacillary / diagnosis
  • Dysentery, Bacillary / epidemiology
  • Escherichia coli Infections / diagnosis
  • Escherichia coli Infections / epidemiology*
  • Escherichia coli O157* / isolation & purification
  • Feces / microbiology
  • Humans
  • Leukocyte Count
  • Logistic Models
  • Mass Screening
  • Middle Aged
  • Prevalence
  • Salmonella Infections / diagnosis
  • Salmonella Infections / epidemiology
  • United States / epidemiology