Epidemiologic Studies of Escherichia coli Diarrheal Infections in a Low Socioeconomic Level Peri-Urban Community In Santiago, Chile

Researchers conducted an age cross sectional cohort analysis of 340 0-47 month old children and newborn cohort analysis of 144 newborns to determine the diarrheogenic Escherichia coli incidence in Santa Julia a low socioeconomic community in Santiago Chile. Children in the age cross sectional cohort had age sex and sector matched controls. The newborns had sex matched controls. A public health nurse or nurse auxiliary visited the household of each subject 2 times a week to detect diarrhea episodes. Between December 1986 and February 1990 the age cross sectional cohort had 1178 episodes of diarrhea and the newborn cohort had 674 episodes. The overall diarrhea incidence was only 2.1 episodes/child/year. An E. coli enteropathogen was isolated in many of these episodes especially during the summer (e.g. enterotoxigenic E. coli [ETEC] 2.2 cases/month in summer vs. 0.4 cases/month in winter; p = .00001). Diffuse adherence E. coli (DAEC) and enteropathogenic E. coli (EPEC) infections also peaked in the summer. ETEC contributed greatly to diarrheal episodes in both cohorts. Among newborns EPEC was isolated significantly more often in cases than controls during the 1st 12 months of life (6.7% vs. 2.5%; p = .021). After 1 year however E. coli isolation rates were essentially the same. On the other hand in the age cross sectional cohort the relative risk of isolation of DAEC rose with age (e.g. 1.1 for 0.11 months 1.4 for 36-47 months and 2.1 for = or > 48 months). In the same cohort DAEC infections were much more common in cases than controls (16.6% vs. 11.9%; p = .0024). Enteroinvasive and enterohemorrhagic E. coli were the most rarely isolated E. coli types. No difference in the isolation rate of enteroaggregative E. coli existed between cases and controls. Since most households in Santa Julia have access to potable water (68%) and an indoor toilet (64%) food contamination were likely the vehicles of E. coli transmission because more than 50% of households do not have a refrigerator.