Objective: The aim of the present study was to isolate E.coli O157:H7 from cattle carcasses in Mashhad abattoir, Iran by conventional culture method and confirmation by a serogroup-specific multiples-PCR assay,. Method & Materials: In this study, during the spring of 2006 totally 120 swab samples were taken from brisket region of bull carcasses aging 2-4 years slaughtered in Mashhad abattoir. The samples were obtained from the post-chilling stage. For isolation of the bacteria at first, the samples were enriched in modified trypticase soy broth containing novobiocin followed by plating on sorbitol Mac Cankey agar supplemented with cifixime and potassium tellurite. The suspected non sorbitol fermenting (NSF) colonies were confirmed as Escherichia coli using biochemical tests (IMViC). Results & Conclusion: In this study a number of 10 NSF Escherichia coli colonies were isolated, and in multiplex-PCR assay 8(6.6%) of samples confirmed as Escherichia coli O157:H7. The second multiplex PCR assay showed that two isolates were harboring the Shiga toxin (stx2) producing gene. The m-PCR assays employed in this study might be considered as a possible alternative for immunological assays detecting somatic and flagellar antigens. Besides it detects the potential of toxin production. The presence of E. coli O157:H7 in cattle carcasses indicated employing improper hygienic practices in Mashhad abattoir and urgent need for implementation of HACCP system.

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