Presence and virulence characterization of Listeria monocytogenes from fish samples in the Black Sea, Turkey

Listeria monocytogenes, characterized by a high mortality rate in humans, is a bacterium that causes listeriosis and is found in various aquatic products. The aim of this research was to investigate the presence, serotype distribution, virulence factor genes, and antibiotic susceptibility of L. monocytogenes strains isolated from a total of 500 fish samples of whiting (Merlangius merlangus euxinus) (n:243) and striped red mullet (Mullus surmuletus) (n:257) caught in the Black Sea between the years 2013-2014. Only one (0.2%) L. monocytogenes strain (striped red mullet) was isolated according to the cultural method (EN ISO 11290-1) and confirmed by PCR analysis. The L. monocytogenes strain was identified as serogroup 4b-4d-4e. Furthermore, the strain harboured hlyA, inlA, inlC, inlJ, plcA, plcB, prfA, mpl, actA, monoA-B, flaA, lip 1-2a, fri, iap, and gtcA genes except the dltA gene. On the other hand, L. monocytogenes strain susceptibility to ampicillin, meropenem, erythromycin, trimetophrim/sulfamethoxazole, and penicillin G was evaluated with the disc-diffusion method. According to the results, serogroup 4b-4d-4e isolated from striped red mullet was found to be unique to raw fish and susceptible to all tested antibiotics. In addition, it is considered that carrying out this research in different seas and with different fish species would be appropriate for determining the prevalence and virulence characteristics of L. monocytogenes.