Caracterização de amostras de Escherichia coli eae positivas isoladas de crianças com diarreia aguda e sem diarreia em Belo Horizonte: tipagem de intimina e pesquisa de hlyA, iha e toxB

Abstract

Infectious diarrhea is still a main cause of morbidity and mortality among children from the less developed areas of the world. Among several etiologic agents, a group of diarrheagenic Escherichia coli (DEC) named attaching and effacing E. coli (AEEC), associated to the genesis of the intimin-mediated A/E lesion in enterocytes, should be mentioned. AEEC includes typical (tEPEC) and atypical (aEPEC) subgroups of enteropathogenic E. coli (EPEC) and the pathotype enterohemorrhagic E. coli (EHEC) that also expresses shiga toxin. All of them, mainly aEPEC, are genetically diverse, especially in regard to the expression of genetic markers of virulence. For these reasons, we carried out this investigation aiming to evaluate the distribution of intimin types and hlyA, iha, and toxB, that encode bacterial adhesins and toxins, in 561 AEEC strains. The strains were obtained from 110 children aged up to 69 months with acute diarrhea and without diarrhea, who searched for assistance at Hospital Infantil João Paulo II/FHEMIG, Belo Horizonte, MG, from 2004 to 2007. Beta was the most prevalent intimin genotype in both tEPEC and aEPEC. Gamma was the most common type among EHEC. Intimin kappa was not found in the population studied. Temporal shifts in the distribution of intimin genotypes were observed: type beta prevalence decreased steadly and epsilon intimin emerged from 2006 on. A higher prevalence of intimin iota was detected among children aged 13 to 24 months. Around 10% of AEEC strains could not have their intimin identified. Seasonality and association with gender and diarrhea were not observed. hlyA, iha and toxB were found in less than 50% of the AEEC strains, but were found to be harbored by all AEEC pathotypes. Our findings corroborate the existence of differences in geographic distribution of the virulence factors encoded by eae, hlyA, iha, and toxB among AEEC. They also support the hypothesis that this pathotype comprises a genetically diverse DEC group, specially the subtype aEPEC.