Probing for virulence and toxigenic genes of Salmonella enterica and Listeria monocytogenes in seafood sold in Rivers State, Nigeria

Abstract

The presence of toxigenic and virulence genes could promote or enhance the degree of pathogenesis in Salmonella enterica and Listeria monocytogenes. This study was conducted to probe for virulence and toxigenic genes of Salmonella enterica and Listeria monocytogenes in seafood sold in Rivers State, Nigeria. A total of 126 raw and parboiled samples of Crassostrea gasar (Oyster) (42), Panaeus monodon (Prawn) (42) and Buccinum undatum (Whelks) (42) were purchased from 3 Local Government Area markets and subjected to standard conventional methods and molecular screening. All Listeria monocytogenes (25) were 100% positive for Dnase, capsule, coagulase, haemolysin and biofilm production (84%); Salmonella enterica (40) were 100% positive for haemolysin, capsule and biofilm production (85%). All isolates were identified molecularly as: Salmonella enterica-AM04528, Salmonella bongori-NCTC12419, Listeria ivanovii-PM-44, Listeria monocytogenes-HN1, Listeria monocytogenes-F6540, Salmonella enterica-19_85, Salmonella enterica-KKP1761, Listeria monocytogenes-NITRR/R1, Salmonella enterica-777SA01, Salmonella enterica-KKP3882, Listeria monocytogenes-HR27 and Listeria monocytogenes-FC3. The toxigenic and virulence genes were present as stn (100%), plcA (100%), hlyA (100%) in all Salmonella enterica and Listeria monocytogenes isolates, and hilA (83.33%) was present in all the Listeria monocytogenes and Salmonella enterica isolates except Listeria monocytogenes-HN1. This study revealed the presence of these genes, which contribute immensely to the pathogenicity of the bacteria posing severe disease conditions. It is necessary to implement regulatory measures to ensure quality control and good hygiene practices in the production, storage and handling of seafood.

Keywords: Seafood, virulence, toxigenic genes, probing, Salmonella enterica, Listeria monocytogenes.