In this study a number of 100 swab samples were taken from brisket region of male cattle carcasses in the range of 2-4 years of age, which were slaughtered in Mashhad abattoir. The samples were obtained from the post-chilling stage of processing. For isolation of the bacteria samples were, firstly enriched in modified trypticase soy broth containing novobiocin, followed by plating on sorbitol Mac Cankey agar supplemented with cifixime and potassium tellurite. Consequently the suspected non sorbitol fermenting (NSF) colonies were confirmed by biochemical tests (IMViC) as Escherichia coli and then employed for multiplex-PCR assay, using primers specific for O157 and H7 antigens gene. For antibiotic susceptibility testing nitrofurantoin, streptomycin, cephalothin, kanamycin, neomycin, ceftizoxime and trimethoprim sulfamethoxazol discs were used and disc diffusion method on Muller hinton agar were employed. For testing the antibacterial effects of some essential oils, the essential oils of Trachyspermum ammi L., Thymus vulgaris, Mentha puleguim and Cuminum cyminum L. were added to blank discs and tested using the same method. Isolated bacteria were respectively susceptible to nitrofurantoin, ceftizoxime, neomycin and kanamycin and also to Trachyspermum ammi L., Thymus vulgaris and Cuminum cyminum L. essential oils. The antibacterial effect of tested antibiotics and essential oils were compareable.

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