PORTEEN KCHINTA SIVA SWETHATANUVASELANGO ASAMUEL MASILAMONI RONALD BSENTHIL KUMAR TMA2024-01-022024-01-022021https://krishikosh.egranth.ac.in/handle/1/5810205328Listeria monocytogenes is an emerging zoonotic pathogen with widespread distribution, the present study has been contemplated to ascertain the presence of L.monocytogenes in foods of animal origin, environmental interface and to determine the serotype, virulence by molecular assay and genotypic characterization of the isolates. Further, antibiotic resistance patterns of the isolates were determined by both phenotypic and genotypic methods and selected essential oils of plant origin were tested for the antimicrobial activity against L.monocytogenes isolates. A total of 474 samples comprising of 274 milk, fifty of each soil, feed, sewage and beef samples were collected from different bovine farms and slaughter house in and around Chennai City, Tamil Nadu, India were screened for the presence of L.monocytogenes by conventional method viz., cultural and biochemical tests and the presumptive colonies were further confirmed by PCR targeting hlyA gene. The overall occurrence of L.monocytogenes in the present study was 2.1 percent (10/474) with high occurrence rate in raw milk samples (8/274), followed by soil (1/50) and beef samples (1/50) while none of the feed and sewage sample were positive for L.monocytogenes by PCR. Serotyping and lineage studies have shown that all the ten confirmed L. monocytogenes isolates were belonging to a single serogroup viz., 1/2a, 3a serogroup (100%) and falls under type II lineage (L2) viz., 1/2a, 1/2c, 3a, 3c serotypes (100%) by multiplex PCR. Further, all the ten L.monocytogenes were studied for various virulence genes and found that iap gene was present in all ten isolates (100%), while plcA and plcB genes were observed in seven (70%) and eight (80%) isolates respectively.EnglishThesis