Toxins of Extraintestinal Escherichia coli Isolated from Blood Culture

Extraintestinal pathogenic Escherichia coli (ExPEC) is one of the main etiological agents of bloodstream infections caused by Gram-negative bacilli. ExPEC pathogenicity is due to the presence of genes, located on plasmids or chromosomes that encode virulence factors. E. coli virulence factors such as adhesins, toxins, invasins are able to modify the metabolism of host cell, contributing to disease. In this study, 80 strains of E. coli were isolated by hemoculture from septicemic patients and examinated by polymerase chain reaction to identify the virulence factors genes encoding toxins and to determine the phylogenetic group. We characterized genes encoding 3 different types of toxins: α-hemolysin (hlyA), cytotoxic necrotizing factor type 1 (cnf1) and five subtypes of cytolethal distending toxins (cdt-I to cdt-V). 23.75% of E. coli strains contained cnf1 gene and 22.5% hlyA. Genes cdt-I and cdt-IV were detected in 1 of 80 strains. Phylogenetic classification showed that E. coli strains fall into 4 groups (A, B1, B2, D) based on PCR detection (chuA and yjaA genes and DNA fragment TSPE4.C2). Virulent ExPEC belong mostly to groups B2 and D. Our results confirmed this fact: 56% of E. coli strains belonged to group B2 and 24% to group D.