Molecular characterization and prevalence of virulence factor genes of Shiga toxin-producing Escherichia coli (STEC) isolated from diarrheic children

Abstract

BackgroundShiga toxin- producing Escherichia coli (STEC), in addition to severe diarrhea, may cause serious and life-threatening complications such as Hemolytic Uremic Syndrome (HUS) in human infections. However, there is no accurate information about the prevalence of these strains in Iran. So this study aimed to investigate the prevalence of serotypes, virulence factors, and antibiotic resistance patterns in STEC isolated from diarrheic children samples. MethodsA total of 315 Stools diarrhea samples were collected, STEC isolates verified by phenotypic and molecular identification methods. Virulence factors, Shiga toxin (Stx), Stx subtyping, serotyping, and antimicrobial resistance genes were detected by PCR methods and sequencing. Cytotoxicity of the Stx positive isolates was examined on Vero cells. ResultsOverall, 150 (47.6%) E. coli were isolated. 10 (6.7%) isolates were confirmed as STEC and Stx1a was identified as the most common Shiga toxin subtype and all of the Stx2 were Stx2a. Serotype O26 was identified in 4 isolates. Iha (70%), lpfA (50%), and Saa (50%) were the predominant virulence factors. The highest toxicity was related to the strain that carried both Stx1 and Stx2 genes simultaneously. The highest rates of resistance were observed against ampicillin and trimethoprim/sulfamethoxazole and the blaCTX-M-15 was the most dominant gene. ConclusionIn this study, indicated other binding virulence factors played a more important role in pathogenicity than intimin in binding. Moreover, virulence factor profile variation causes differences in STEC pathogenesis. Antibiotic resistance with high cytotoxicity in STEC isolates should be considered as a warning to public health.