RESUMEN
Childhood diarrheal diseases remain highly endemic in northeastern Brazil. The attributable fraction of all diarrheal diseases among children less than 2 years of age due to Escherichia coli was examined in a 2 year prospective study in two large urban centers of Brazil. Between May 1997 and June 1999, fecal E.coli isolates from 237 children with diarrhea (217 acute and 20 persistent cases) and 231 children without diarrhea (controls) attending two hospitals in Northeast Brazil were tested for their pattern of adherence to HEp-2 cells and for colony hybridization with DNA probes specific for the six pathotypes of diarrheagenic E.coli. Enteroinvasive E.coli, enterotoxigenic E.coli and enterohemorrhagic E.coli were not isolated from any children. Diffusely adherent E.coli (DAEC) and enteroaggregative E.coli (EAEC) were the most frequent isolates with similar frequencies from children with or without diarrhea. Atypical EPEC (EAF-negative) strains were isolated with similar frequency from both cases 5.5 per cente and controls 5.6 per cente. Enteropathogenic E.coli (typical EPEC) strains, characterized by localized adherence pattern of adherence, hybridization with the EAF probe, and belonging to the classical O serogroups, were significantly associated with diarrhea (P=0.03). These E.coli strains associated with diarrhea accounted for 9 per cente of all children with diarrhea. Collectively, in Northeast Brazil, E.coli strains comprise a small proportion of severe diarrhea prevalence in children.