Virulence genes and pulsed-field gel electrophoresis profiles of Shiga toxin-producing Escherichia coli isolated from different food samples and patients with acute diarrhea.

ABSTRACT

Background and Objectives: Escherichia coli O157 H7 is one of the most important causes of hemorrhagic colitis, and hemolytic uremic syndrome. The present study aimed to isolate E. coli O157 H7 from foods and patients with hemorrhagic colitis, and identify Shiga toxin genes, phylogenetic comparison, and antibiotic resistance of the isolates. Materials and Methods: In total 400 samples, including patients stool and food were taken in Isfahan-Iran province. Phenotypic tests and PCR were performed to identify Shiga toxin-producing E. coli. The isolated strains were compared phylogenetically by PFGE. Agar disk diffusion was performed to identify the antibiotic resistance of the isolates. Results: Totally, 5 isolates of fecal samples were E. coli O157, but only 2 isolates carried H7 gene. Also, 9 isolates of E. coli O157 were isolated from food samples that 3 isolates were E. coli O157 H7. The isolates carried stx1, stx2, hlyA and eaeA genes. Also, E. coli non-O157 H7 identified from samples that contained stx1, stx2, hlyA genes. The highest susceptibility to imipenem and the highest resistance to ampicillin and ciprofloxacin were observed. There was a similarity of 100% between the E. coli O157 H7 strains isolated from patients and raw milk and minced beef samples. Conclusion: Serotypes other than the O157 of E. coli are more prevalent in patients and food. The E. coli O157 H7 isolates from patients had 100% genetic similarity with minced meat and cow milk isolates, which indicates cattle are the most important reservoir of this bacterium in Iran.