Listeria monocytogenes in salmonid slaughter facilities - Screening program for the Norwegian Food Safety Authority

Abstract

Listeria monocytogenes is a bacterium of special concern in the seafood industry beacuse it possesses several properties adapted for the food production environment and may cause severe disease in humans. The Institute of Marine Research has on behalf of the Norwegian Food Safety Authority conducted a screening program for L. monocytogens in salmonid slaughter facilities. In total, 358 samples from 60 slaugher facilities (49 slaughtering plants and 11 slaughtering vessels) were examined. Samples were collected from the production environment (n=108), from the surface of fish entering the facilities (n=47), and from the surface of fish (n=59) and raw material (n=144) at end point at the examined facility. None of the samples from the slaughtering vessels were positive for L. monocytogenes, whereas 22 positive samples were detected in nine different slaugtering plants. In five of these plants, several positive samples were found. Six of the slaughtering plants had positive samples at the end of the production line, where a higher prevalence was found when swabbing the fish skin and gills compared to the examined raw matierial. All the raw material samples contained low numbers of L. monocytogenes below the quatification limit (<10 CFU/g). However, this study found that L. monocytogenes can be present in both fish and the production environment, and that in some cases L. monocytogenes will be present in fish ready for furhter processing in the salmonid value chain.