Isolation and PCR identification of Listeria spp. from fishes of Cochin area

Abstract

Listeria spp, a Gram positive and non-spore forming bacteria, are widely distributed in nature and different food products. Among Listeria spp., only Listeria monocytogenes is considered as potential human pathogen. In this study, we have screened fish samples procured from local markets of Cochin for the presence of Listeria spp. including L. monocytogenes. 25.7 % of the samples tested were found to harbour Listeria spp. The incidence rate of Listeria spp. in finfish, prawn and clam were found to be 26.8 %, 10 % and 37.5 %, respectively. But L. monocytogenes has not been detected in any of the fish samples tested. Listeria innocua was found to be the most prevalent species of Listeria. The isolates were characterized by Listeria genus specific PCR as well as L. monocytogenes, L. innocua & L. ivanovii species specific PCR. All of our L. innocua isolates have been confirmed by both genus and species specific PCR. For confirmation of species of Listeria, PCR has been shown to be an effective tool.