Abstract

Enteropathogenic Escherichia coli (EPEC) strains are important agents of infantile diarrhea all over the world. In contrast to other diarrheagenic Escherichia, EPEC does not produce any classic protein toxin but induces diarrhea by intimate binding to intestinal cells. Diarrhea is the result of a series of signals triggered by the pathogen-host membrane interaction, which in turn provokes reorganization of the cytoskeleton of the affected cell, with a consequent loss in microvillus structure and effacement of intestinal villi. This lesion is called attaching and effacing (A/E).³

EPEC infections undertake greater importance in developing countries since the rate of infection and consequent infantile mortality reaches higher level. With respect to animals, EPEC have been isolated from various species but most isolates belong to serotypes that differ from those recovered from man. Furthermore, human serotypes isolated from animals usually exhibit different phenotypic and/or genotypic characteristics when compared with human strains, receiving the denomination of atypical EPEC.

Recently we demonstrated that in the case of nonhuman primates, several isolates belong to serogroups and/or serotypes related to those implicated in human disease, such as the traditional EPEC serogroups O127, O128, O142, and O26. In addition, the nonhuman primate strains showed genotypic and phenotypic characteristics similar to those of human typical EPEC serotypes indicating that not only man, as has been postulated, but also those animals, may represent a natural reservoir and source of infection of these bacteria for both, human and nonhuman primates.²

The objective of this study was to evaluate genetic differences among strains isolated from nonhuman primates compared with human collection strains, through the analysis obtained by the random amplified polymorphic DNA (RAPD). This method has been considered as an appropriated molecular tool in epidemiologic analyses of E. coli. The study included a total of 18 EPEC strains isolated from healthy and sick nonhuman primates, being phenotypic and genotypic strain characteristics described elsewhere.² Thirteen human EPEC strains recovered from sick children were obtained from culture collections kept at Instituto Adolfo Lutz, São Paulo, Brazil, a reference center for E. coli serotyping. The assay was performed using three different primers as described before¹ and the analysis done at a Numerical Taxonomy and Multivariate Analysis System-pc program (1.7 version) generated a dendrogram.

Dendrogram analysis showed that there was not clustering between human and monkey strains. Two main groups were distinguished. The first one included all human and nonhuman primate strains belonging to serogroup O26, all of them recovered from sick individuals. In the second group, two subgroups were defined, one mostly composed of strains isolated from healthy nonhuman primates besides human isolates, and the other composed of strains obtained from sick individuals. In this last cluster the nonhuman primate strains showed genotypic characteristics of typical human EPEC,² even when they did not belong to classic human serotypes. Human and nonhuman isolates of the EPEC serotypes O127:H40 and O128:H2 shared, respectively, 85% and 80% of their bands indicating strong genetic similarity between the strains, allowing for speculation that they have arisen from the same pathogenic clone.

The results of this study provide further evidence that monkey EPEC (MEPEC) are correlated to human EPEC as pointed out in prior research.² Due to nonhuman primates phylogenetic proximity to man and their similar susceptibility to human pathogens, they could represent important experimental models for the study of EPEC infection. The potential risk of transmission between human and nonhuman primates should be considered in order to minimize the impact these bacteria may have on the health of colonies of animals held in captivity.

Acknowledgment

This work was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) and by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq).

Literature Cited

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2.  Carvalho, V.M., C.L. Gyles, K. Ziebell, M.A. Ribeiro, J.L. Catão-Dias, I.L. Sinhorini, J. Otman, R. Keller, L.R. Trabulsi, and A.F. Pestana de Castro. 2003. Characterization of monkey enteropathogenic Escherichia coli (EPEC) and human typical and atypical EPEC serotype isolated from neotropical nonhuman primates. J Clin Microbiol. 41:1225–1234.

3.  Trabulsi, L R., R. Keller, T.A.T. Gomes. 2002. Typical and atypical enteropathogenic Escherichia coli. Emerg Infect Dis. 8:508–513.