Etiologia da diarréia infantil na região metropolitana do Rio de Janeiro: caracterização de possíveis marcadores de virulência em Escherichia coli enteropatogênica (EPEC) e de uma adesina relacionada ao fenótipo agregativo em amostras que coexpressam adesão localizada

Abstract

In this study, we have demonstrated the participation of enteroaggregative Escherichia coli (EAEC) as the main enteropathogen presently associated with infant diarrhea in Rio de Janeiro city. In addition, we have demonstrated a reduction in occurrence of typical enteropathogenic Escherichia coli (EPEC) in comparison with studies conducted in the early 90s in the same area. A detailed analysis of the EPEC strains identified revealed the occurrence of some strains belonging to non-classic EPEC serogroups and/ or expressing a peculiar pattern of adherence characterized by coexpression of the localized (LA) and aggregative (AA) pattern of adherence. Strains presenting AL/AA were able to form biofilms in both biotic and abiotic surfaces. In one particular strain, we have demonstrated that this hybrid phenotype (LA/AA) was surprisingly associated with the expression of the EPEC fimbrial adhesin BFP (bundleforming pilus). The additional ability to form biofilms may lead to the emergence of a new EPEC pathotype, which could be more adapted to colonize and persist in the intestinal tract. The occurrence of E. coli strains co-expressing LA/AA might be further analyzed and monitored in other geographic regions. Furthermore, in this study, we observed a large variety of atypical EPEC serotypes and different combinations of virulence markers were also found; some of these atypical EPEC strains were associated with persistent diarrhea and possibly with dysentery (bloody diarrhea). Finally, some typical EPEC (three) and atypical EPEC (two) strains isolated and characterized in the present study showed the AA phenotype and were isolated from patients co-infected by EAEC, thus suggesting that this phenotype was acquired by horizontal transmission from the EAEC strains which were found co-inhabiting the gut of these patients.