Potencial patogênico de cepas de Escherichia coli Enteropatogênicas atípicas (aEPEC) isoladas de cães e humanos com sintomas de diarreia

Abstract

In recent decades, atypical Enteropathogenic Escherichia coli (aEPEC) strains have emerged as an important pathogen associated with childhood diarrhea around the world, incluinding Brazil. aEPEC are commonly found in different animal species, including companion animals such as dogs, where some strains share the same serotype, virulence genes, and exhibit a genetic correlation with human strains. Although, the role of aEPEC as a zoonotic agent is not yet fully elucidated. In the present study, the genotypic and phenotypic characteristics of virulence was evaluated among two groups of aEPEC strains of the O4:H16, O11: H16, O49: H10 and O51: H40 (2) serotypes, isolated from puppies with diarrhea (n = 5) and from cases of childhood diarrhea in Brazil (n = 5), in order to determine the pathogenic capacity of these strains when transmitted to humans. We evaluated: (i) the presence of virulence factors by PCR (ecpA, hcpA, iha, paa, csgAB, saa, pilS, toxB, ehxA, espP and 16 nle genes) and phenotypic tests (expression of curli and T1F fimbrias); (ii) the phylogenetic relationship and the clonality between the strains by MLST and PFGE; (iii) the ability to adhere, invade and survive inside the intestinal cells by “in vitro” assays. The occurrence of virulence genes was similar between canine and human strains and the ecpA, csgAB and hcpA genes were found in most strains, whereas efa-1 and toxB occurred only in O4: H16 and O49: H10 serotypes, respectively. Strains of the same serotype showed a similar nle genes profile, with the presence of nleB and nleE genes in O4:H16 and O51:H40 serotypes. The STs 10 (serotypes O4: H16, O11: H16 and O51: H40) and 206 (O49: H10) were identified and the PFGE dendogram showed clustering between strains of the same ST and serotype, although the occurrence of clones among the canine and human isolates was not observed. Strains of both origins showed the LAL adhesion phenotype in HEp-2, Caco-2 and T84 cells. In addition, all strains demonstrated the ability to invade and survive for at least 48 hours in polarized monolayers of the T84 human intestinal lineage. To date, these findings indicate that puppies carry aEPEC strains potentially pathogenic to humans, which in a poor hygiene environment, can be transmitted to a susceptible population, especially children under 2 years of age, leading to diarrheal disease.