Resumo

Enteropathogenic Escherichia coli (EPEC) are an important cause of gastroenteritis in children less than two years of age. The EPEC pathotype is sub-divided into typical EPEC (tEPEC), which carry the large virulence EAF (EPEC adherence factor) plasmid, and atypical EPEC (aEPEC), which lack this plasmid. The chromosomal pathogenicity island (PAI) termed locus of enterocyte effacement or LEE region encodes several proteins that play a major role in typical and atypical EPEC pathogenesis. Besides the LEE region, other PAIs have been found on prophages and on integrative elements in the chromosome of EPEC strains. Recent studies have shown that the effector repertoire of EPEC is much larger than previously thought and is not restricted to the LEE-encoded proteins. In the present study, we examined a total of 107 EPEC strains (44 typical and 63 atypical), isolated from 71 diarrheic and 36 non-diarrheic children in Brazil for the presence of six non-LEE-encoding genes (cif, espI/nleA, nleB, nleC, nleD, and nleE) by colony hybridization under stringent conditions, using as probes fragments of these genes obtained by PCR and labeled with [³²P] dCTP. Regarding the prevalence of the non-LEE genes, nleC and espI/nleA were the most prevalent, followed by cif, nleB, nleE and nleD. Three of the six non-LEE-encoding genes examined (nleC, cif and nleB) were significantly more prevalent in tEPEC than in aEPEC strains. The only gene found in association with diarrhea was espI/nleA in tEPEC strains. To note, none of the non-LEE-encoding genes investigated was found in association with diarrhea among the aEPEC strains studied. Even though the non-LEE-encoding genes were more prevalent in tEPEC than in aEPEC, a higher diversity of combinations of these genes (genetic profiles) was observed in aEPEC. The varied repertoire of the non-LEE effector genes found between distinct EPEC serotypes may suggest that different isolates can employ distinct infection strategies. The heterogeneity of aEPEC strains studied makes it difficult to identify the truly pathogenic isolates in the group bringing direct implications in the diagnostic strategies.