Molecular-genetic characteristics of strain Escherichia coli serogroup O26 causing diarrheal diseases in children

Abstract

Aim. To determine the serotype and virulence factors of the E. coli serogroup O26 isolated from children with diarrheal syndrome. Materials and methods. Fifty-three strains of E. coli O26 isolated in 2014-2016 from the stool of children with clinical manifestations of acute intestinal infection in Saint Petersburg were studied. Phenotypic (enzymatic and antigenic properties), molecular genetic [detection of virulence genes of enteropathogenic (EPEC - eae, bfp, hlyA), and enterohemorrhagic (EHEC - eae, stx1, stx2, ehxA), genes encoding O- and H-antigens (rfb and fliC), genes, defining phylogenetic group (chuA, yjaA и TspE)] methods were used. The phylogenetic group and the production Shiga toxins were determined. Results. All strains were identical to the antigen characteristics of serotype O26:H11 and phylogenetic group B1. Two pathogroups were created based on the set of virulence genes: a-EPEC (64.2%) and EHEC (35.8%). Strains EHEC produced Shiga-toxin 1, encoding gen stx1. No differences in enzymatic activities were found between the strains of E. coli О26:H11 for EPEC and EHEC strains. Conclusion. In the population of E. coli O26:H11, which caused acute intestinal infection in children in Saint Petersburg, more than 30% of the strains belonged to the highly virulent group EHEC. Molecular-genetic methods should be used for reliable detection of pathogens.