Listeria monocytogenes is an important food borne pathogen with a high case fatality rate. Among 13 different serotypes of this bacterium, 4 serotypes (1/2a, 1/2b, 1/2c, and 4b) were considered as the main cause of listeriosis outbreaks. The aim of this study was to identify the major serotypes and virulence genes inListeriamonocytogenes isolated from chicken carcasses which were collected from different supermarkets and butcheries in Mashhad. Among the 80 isolated Listeria spp., most of themidentified as L. monocytogenes (36 out of 80). Most of theL.monocytogenes isolates belonged to IIbserogroup (50%) which contains 1/2b and 3b serotypes. The second and third major serogroupswereIVa (27.77%) and IIa (19.44%).SerogroupIVb (2.77%) which contains 4b serotype was the fourth major isolates.In order to differentiate serotype 1/2a and 3a from 1/2c, amplification of flaAgenewas used. L. monocytogenesisolateswere also examined for the presence of inlC, inlJ and hlyA virulence genes. 26 out of 36 isolates were positive for inlC, and inlJ,whereashlyA gene was detected in 32 isolates.Chicken carcasses may act as a source of infectious listeriosis for human in this area.

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