Phenotypic and genetic analysis of diarrhea-associated Escherichia coli isolated from children in the United Kingdom

Background: A hospital-based study was performed to (1) compare phenotypic and genotypic diagnostic tests for enteropathogenic Escherichia coli, enter oaggregative E. coli, and diffuse-adhering E. coli (collectively termed adh erent E. coli) and (2) to assess the importance of these different classes of adherent E. coli as causes of infant diarrhea in the United Kingdom in c omparison with other enteropathogens. Methods: E. coli isolated from 1,496 infants with diarrheal disease and fro m 546 age-related controls were screened for enteropathogenic E. coli, ente roaggregative E. coli, and diffuse-adhering E. coli using HEp-2 cell adhere nce assays and DNA probes. Results: Marked discrepancies between the phenotype and genotype of isolate s indicate significant heterogeneity among enteroaggregative E. coli and di ffuse-adhering E. coli strains. Depending on the assay used, adherent E. co li were isolated as the only putative pathogen in 23% to 27% of diarrhea ca ses, a significantly higher incidence than in the control group. Individual ly, enteroaggregative E. coli (8.5-8.6% of cases) and diffuse-adhering E. c oli (10.4-11.3% of cases), but not enteropathogenic E. coli (4.5-7.5%, of c ases), were significantly associated with diarrhea. Conclusions: These studies indicate that adherent E. coli may be an importa nt cause of diarrhea in infants in the United Kingdom; they also emphasize the need for more specific virulence-based tests for these putative classes of "diarrheagenic" (diarrhea causing) E. coli.