[Virulence genes of verotoxigenic E. coli isolated from raw milk and unpasturized cheese]

ABSTRACT

Verotoxigenic strains of E. coli mostly contain one or both of stx1 and stx2 genes. Both of these genes play a role in pathogenicity of the bacteria. These strains cause bloody diarrhea, uremic haemolytic syndrome and purpura thrombocytopenia. Because of a high probability of the presence of verotoxigenic strains of E. coli in various foods, especially milk and cheese, and due to the importance of these strains to human health, we aimed to determine the presence of verotoxigenic strains of E. coli in unpasteurized milk and cheese by PCR. In this study, 200 samples of raw milk and 80 samples of unpasteurized cheese were collected, and verotoxigenic E. coli were isolated using selective media. PCR was used to determine some virulence genes including stx1, stx2, eaeA and hlyA. Thirty-eight and 14 E. coli samples were isolated from raw milk and unpasteurized cheese, respectively. The isolates were examined by PCR in order to find the O157H7 specific DNA and stx1, stx2, eae and hlyA genes. Two out of 38 isolates originating from raw milk were typed as O157H7, both of them containing stx2, eaeA and hlyA genes. Another isolate, which was not O157H7, also contained the stx2 gene. No isolates possessed the stx1 gene. None of the isolates originating from unpasteurized cheese samples contained any of the virulence genes