Serogroup identification and Virulence gene characterization of Listeria monocytogenes isolated from chicken carcasses

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 is to identify the major serotypes and virulence genes in Listeria monocytegenes isolated from chicken carcasses which were collected from different supermarkets and butcheries in Mashhad. Among the 80 isolated Listeria spp., most of them were identified as L. monocytogenes (36 out of 80). Most of the L. monocytogenes isolates belonged to serogroup llb (52.77%) which contains 1/2b and 3b serotypes. The second and third major serogroups were IVa (27.77%) and IIa (16.66%). Serogroup IVb (2.77%) which contains 4b serotype was the fourth major isolate. In order to differentiate serotype 1/2a and 3a from 1/2c, amplification of flaA gene was used. L. monocytogenesis isolates were also examined for the presence of inlC, inlJ and hlyA virulence genes. 26 out of 36 isolates were positive for inlC, and inlJ, whereas hlyA gene was detected in 32 isolates. Chicken carcasses may act as a source of infectious listeriosis for humans living in this area.