Screening of Zoonotic Listeria spp. in Milk and Dairy Products by Conventional Method and PCR

Abstract

The present study was conducted to study the prevalence of zoonotic Listeria monocytogenes in milk and dairy products. About 567 samples comprising of milk and dairy products were collected randomly from several retail outlets and supermarkets in different zones of Chennai, India. Out of 567 samples, 9 (1.58%) were positive for Listeria spp. by conventional culture method. The occurrence of Listeria spp. in heat and acid coagulated dairy products, frozen dairy products and other dairy products like butter and cheese was 2 (6.06%), 3 (9.37%) and 4 (8.69%) respectively, while Listeria spp. was not detected from other dairy products analysed. Further, confirmation by biochemical characterization revealed 7 isolates of L. welshimeri. Moreover, the polymerase chain reaction targeting the virulent hlyA gene of Listeria monocytogenes revealed that none of the samples screened were positive for L. monocytogenes.