Prevalence of listeria monocytogenes in ready-to-eat seafood marketed in Thessaloniki (Northern Greece)

Abstract

Aim: In the current study, a contribution to the knowledge on the prevalence and level of contamination of Listeria monocytogenes in ready-to-eat (RTE) seafood marketed in Thessaloniki (Northern Greece) was provided; the serovar identity of the L. monocytogenes isolates was also determined. Materials and Methods: A total of 132 RTE seafood samples consisting of 74 smoked fish products, 18 salted fish products, 16 dried fish products, 9 raw marinated fish products, 10 cooked marinated cephalopods and 5 surimi crab stick products were analyzed. L. monocytogenes were isolated and enumerated based on ISO 11290-1/A1 and ISO 11290-2/A1 protocols, respectively, and identified using a multiplex polymerase chain reaction (PCR) system utilizing genus and species specific primers. For the identification of serotypes a second multiplex PCR assay was used which clusters L. monocytogenes strains into four major serogroups. Results: Of the samples examined, 11 (8.3%) proved positive for Listeria spp. with 8 (6.1%) yielding L. monocytogenes. Only in one sample of smoked mackerel the level of L. monocytogenes exceeded the legal safety limit of 100 cfu/g set out in Commission Regulation (EC) No. 1441/2007. Serotyping showed higher percentages of isolates belonging to PCR serogroup 3:1/2b, 3b, 7 (46.7%) and serogroup 1:1/2a, 3a (40%) followed by serogroup 4:4b, 4d, 4e (13.3%). Conclusion: This study demonstrated that L. monocytogenes can be isolated from processed RTE seafood products at retail in Thessaloniki (Northern Greece) in low concentrations. However, the presence of this human pathogen in RTE seafood should not be overlooked, but it should be considered as having significance public health implications, particularly among the persons who are at greater risk. Therefore, RTE seafood should be produced under appropriate hygienic and technological conditions since the product does not undergo any treatment before consumption.