Abstract

The aim of this study was to investigate the virulence potential of the isolated bovine STEC for humans in Iran. In this study a collection of STEC strains (n = 50) had been provided via four stages, including sampling from feces of cattle, E. colt isolation, molecular screening of Shiga toxin (stx) genes, and saving the STEC strains from various geographical areas in Iran. The STEC isolates were subjected to stx-subtyping, O-serogrouping, and phylo-grouping by conventional polymerase chain reaction (PCR). Occurrence of stx1 (52) and stx2 (64) was not significantly different (p = 0.1), and 16 of isolates carried both stx1 and stx2, simultaneously. In addition, 36 and 80 of the isolates were positive for eae and ehxA, respectively. Molecular subtyping showed that stx1 a (52), stx2a (44), stx2c (44), and stx2d (30) were the most prevalent subtypes; two combinations stx2a/stx2c and stx2c/stx2d coexisted in 18 and 10 of STEC strains, respectively. Three important non-O157 serogroups, including O113 (20), O26 (12), and 0111 (10), were predominant, and none of the isolates belonged to O157. Importantly, one 026 isolate carried stxl, stx2, eae and ehxA and revealed highly virulent six subtypes. Moreover, all the 21 sero-grouped strains belonged to the B1 phylo-type. Our study highlights the significance of non-O157 STEC strains carrying highly pathogenic virulence genes in cattle population as the source of this pathogen in Iran. Since non-O157 STEC strains are not routinely tried in most diagnostic laboratories, majority of the STEC-associated human infections appear to be overlooked in the clinical settings. (C) 2017 Published by Elsevier Ltd.