Characterization and Analysis of the Virulence Profile of atypical enteropathogenic Escherichia coli strains isolated from outbreaks and sporadic cases of diarrhea in different geographical regions of Brazil.
Enteropathogenic Escherichia coli (EPEC) represents an important cause of diarrhea in industrialized areas, but also has been identified in less-developed countries, such as Brazil. So far, the most important mechanism of virulence identified in EPEC strains comprises the establishment of a histopathological lesion termed attaching and effacing (AE). The AE lesion is characterized by intimate bacterial adherence, microvillus effacement and accumulation of polymerized actin and other cytoskeleton elements, resulting in pedestal-like structures underneath adherent bacteria. Since 1995, the EPEC are divided into two subgroups: typical (t-EPEC) and atypical EPEC (a-EPEC), based on the presence of the pEAF (EPEC adherence factor plasmid) in the t-EPEC, and its absence in the a-EPEC. Epidemiological studies performed in Brazil, as well in others less-developed countries from the year 2000, have been reported the isolation of a-EPEC in a significantly higher frequency than the isolation of t-EPEC. However, the a-EPEC has been isolated, in some of these studies, in similar frequency from children with diarrhea, as well as from healthy children, making hard to associate the a-EPEC strains as agent of gastrointestinal tract infections. The difficulty in associating the a-EPEC with the diarrheal disease can be attributed to the heterogeneity of these isolates. Studies focusing in the phenotypic and molecular characterization of a-EPEC isolates, have clearly demonstrated that subpopulations of this pathotype can be isolated more often from individuals with diarrhea, than from healthy individuals. The association of a-EPEC as agent of gastrointestinal tract infections can be reinforced by the involvement of this bacteria in diarrhea outbreaks, involving not only children but also adults. Such observation emphasizes the need to explore the a-EPEC isolates, looking for virulence markers that could contribute in the identification of the potentially pathogenic a-EPEC, in this heterogeneous group of strains. This study aims to characterize and evaluate the presence of important virulence markers in a-EPEC strains isolated from outbreaks and sporadic cases of diarrhea in Brazil.
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