EPIDEMIOLOGIC STUDIES OF ESCHERICHIA-COLI DIARRHEAL INFECTIONS IN A LOW SOCIOECONOMIC LEVEL PERIURBAN COMMUNITY IN SANTIAGO, CHILE

The incidence of diarrhea due to sir: categories of diarrheogenic Esch erichia coli was determined in two pediatric cohorts in a low socioeco nomic level community in Santiago, Chile, with access to chlorinated w ater. An age cross-sectional cohort of 340 children aged birth to 47 m onths was assembled. A newborn cohort was assembled by enrolling 10-12 newborns monthly for 12 months. Episodes of diarrhea were detected by twice weekly household visits. E. coli from stool cultures of cases a nd matched controls were hybridized with DNA probes specific for enter otoxigenic, enteroinvasive, enteropathogenic, enterohemorrhagic, enter oaggregative, and diffuse adherence E. coli. Overall, the incidence of diarrhea was low (2.1 episodes/infant/year). Nevertheless, a putative E. coli enteropathogen was found in a large proportion of diarrheal e pisodes, particularly during the summer. In both cohorts, enterotoxige nic E. coli were important pathogens. Enteropathogenic E. coli were in criminated during the first year of life in the newborn cohort, where they were found significantly more often in cases (p = 0.021) than in controls; beyond this age, isolation rates were similar. In contrast, the relative risk of isolation of diffuse adherence E. coli increased with age in the age cross-sectional cohort, where, overall, the differ ence in rate of isolation between cases and controls was significant ( p = 0.0024). Enteroinvasive and enterohemorrhagic E. coli were isolate d infrequently. Enteroaggregative E. coli were encountered equally in cases and controls. Facile transmission of E. coli enteropathogens is occurring in this community despite the availability of potable water.