SUMMARY: Diarrheagenic Escherichia coli (DEC) is an important agent of endemic and epidemic diarrhea worldwide, particularly in developing countries. DEC cannot be differentiated from commensal E. coli on selective media, although there are a few exceptions. Most studies use the colony isolation method, which cannot detect low numbers of DEC, and therefore, these studies might underestimate the incidence of DEC. In the present study, we employed a colony sweep method with real-time PCR targeting virulence genes of 5 categories of DEC; this technique can detect very low numbers of DEC among hundreds of commensal E. coli. DEC was detected in 171 (55.9z) of 306 children with diarrhea in Kenya. The prevalence of DEC in Kenya was notably higher than that (30 in 143, 21.0z) in Indonesia. Occurrences of multiple DEC infection in Kenya were frequent (69 in 306, 23.2z), suggesting that the source of DEC infection may be related to grossly contaminated food and water. In contrast, only 9 (6.0z) of 150 healthy adults in Kenya carried DEC. Considering that healthy adults naturally harbor non-DEC, it is interesting how children exclude DEC but not non-DEC as they grow up. Several mechanisms, such as mucosal immunity and intestinal microbiota, might be involved in the exclusion of DEC.

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