Isolation and identification of Listeria spp. in chicken carcasses marketed in northeast of Iran

The aim of the present study was to evaluate the contamination of chicken carcasses with Listeria spp. Also, the antibiotic susceptibility of the Listeria monocytogenes isolates were investigated. In this study, 200 fresh chicken carcasses were examined for the presence of Listeria spp. Presumptive isolated Listeria colonies were confirmed by m-PCR. From 200 fresh chicken carcasses samples which were collected randomly from different supermarkets and butcheries, 80 samples (40%) were detected as contaminate with Listeria spp. and 18% of the isolates identified as Listeria monocytogenes (L. monocytogenes) using multiplex PCR assay. Conventional methods were used to differentiate other species of the Listeria genus. The results showed the most prevalent isolates is L. monocytogenes (18%). Other isolates were detected as Listeria innocua (11.5%), Listeria grayi subspp. murrayi (8%), Listeria grayi subspp. grayi (1.5%) and Listeria welshimeri (1%). The Majority of the isolates had multidrug resistance to commonly used antibiotics. Most of them were resistant to erythromycin (52.77%), followed by Tetracycline (44.44%), Clindamycin (41.66%), and Trimethoprim (25%). Some of them showed resistance to chloramphenicol (16.66%). The results indicate the noticeable contamination of fresh chicken carcasses with Listeria spp. Resistance of the L. monocytogenes isolates to antimicrobials commonly used to treat human listeriosis, which could be a potential health hazard for consumers.