Seventy-six children <2 years old were prospectively followed for 1 year in a peri-urban community of Mexico City to determine asymptomatic infection and acute diarrhea associated with diarrheagenic Escherichia coli pathotypes (DEPs). By use of a pathogen-specific multiplex PCR, DEPs were sought in 795 stool samples, of which 125 (16%) were positive for DEP; of these, 4 represented shedding episodes and 4 parasite coinfections. Most single-DEP infections (85/117) were asymptomatic (P < 0.001), and of the 32 DEP diarrhea episodes, 41% were associated with atypical enteropathogenic E. coli (aEPEC), 37.5% with enterotoxigenic E. coli, 9% with typical EPEC, 9% with enteroinvasive E. coli, and 3% with Shiga toxin-producing E. coli strains. Among the 76 children, 54 had at least one stool positive for DEP, of which 23 experienced a DEP-associated diarrhea episode. In the last group of children, DEP infection was significantly associated with a diarrhea episode (relative risk [RR] ‫؍‬ 2.5; 95% confidence interval [CI], 1.79 to 3.57; P < 0.001), with ETEC (RR ‫؍‬ 2.30; 95% CI, 1.49 to 3.54; P ‫؍‬ 0.003) and aEPEC (RR ‫؍‬ 1.92; 95% CI, 1.23 to 3.0; P ‫؍‬ 0.019) being the pathotypes associated with diarrhea. aEPEC-associated diarrhea episodes were frequently in the <12-month age group (RR ‫؍‬ 2.57; 95% CI, 1.05 to 6.27; P ‫؍‬ 0.04). aEPEC infections were distributed all year round, but associated diarrheal episodes were identified from April to October, with a May-June peak (rainy season). Most ETEC infections and diarrhea episodes characteristically occurred during the summer (rainy season), with a diarrhea peak in August. Of all DEPs, only aEPEC was associated with acute diarrhea episodes lasting 7 to 12 days (P ‫؍‬ 0.019). DEPs are important causes of community-acquired enteric infection and diarrhea in Mexican children.Diarrheal diseases continue to be a health problem worldwide (4, 16), especially in developing countries, where they are estimated to be responsible for 2.5 million infant deaths per year, with an annual mortality rate of 4.9 per 1,000 children and an incidence of 3.2 episodes per child per year among children under 5 years of age (16). Diarrheagenic Escherichia coli pathotypes (DEPs) represent a leading bacterial cause of pediatric diarrhea in developing regions (21), with some responsible for traveler's diarrhea (21, 27), and are also an emerging cause of diarrhea in industrialized countries (6, 29). The DEPs that cause diarrhea include enteropathogenic E. coli (EPEC), enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), Shiga toxin-producing E. coli (STEC), diffusely adherent E. coli, and enteroaggregative E. coli (15,21). These pathotypes are defined by the presence or absence of one or more definable E. coli virulence factors. However, a less well-characterized DEP is atypical EPEC (aEPEC), which carries the attaching and effacing intimin (eaeA) gene of typical EPEC (tEPEC) strains but lacks the plasmid-mediated bundle-forming pilus (bfp) of tEPEC and Shiga toxins 1 and 2 (21, 31).Althoug...

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These results suggest that the effect of vitamin A supplementation on clinical outcomes may be pathogen dependent.

Street-vendors in Mexico City provide ready-to-eat food to a high proportion of the inhabitants. Nevertheless, their microbiological status, general hygienic and trading practices are not well known. During spring and summer 2000, five tianguis (open markets) were visited and 48 vendors in 48 stalls interviewed. A total of 103 taco dressings were sampled for E. coli and Salmonella spp.: 44 (43%) contained E. coli and 5 (5%) Salmonella (2 S. Enteritidis phage type 8, 1 S. Agona, 2 S. B group). Both E. coli and salmonellas were isolated from three samples. Of Salmonella-positive stalls 80% (4/5) had three or more food-vendors and 80% of vendors were males, compared with 37.3% (16/43) and 46.4% (20/43) in the Salmonella-negative stalls respectively. Food-vendors kept water in buckets (reusing it all day), lacked toilet facilities, and prepared taco dressings the day before which remained at the tianguis without protection for 7.8 h on average. Consumption of street-vended food by local and tourist populations poses a health risk.