PREVALENCE AND TYPING OF LISTERIA MONOCYTOGENES STRAINS IN RETAIL VACUUM-PACKED COLD-SMOKED SALMON IN THE REPUBLIC OF IRELAND

The prevalence of Listeria monocytogenes in five brands (A, B, C, D and E) of vacuum-packed pre-sliced cold-smoked salmon (n = 120) marketed in different retail outlets in the Republic of Ireland was investigated. The prevalence of L. monocytogenes in the cold-smoked salmon was 21.6%. The L. monocytogenes strains isolated from the prevalence studies were typed by using Multi-Locus Variable number tandem repeat Analysis; this method confirmed the type division among the L. monocytogenes isolates. A minimum spanning tree showed that isolates from brand A clustered together. Few isolates from brand B, C, D and E showed genetic similarities, while others were spread throughout the cladogram. The genetic distinction among subtypes may be processor-specific, while the similarities among the subtypes support the hypothesis of well-adapted clones of L. monocytogenes in the fish industry. The results highlight the need for food safety control at both preprocessing and processing stages, as there is no bactericidal process involved to eliminate any pathogen during the processing of cold-smoked salmon.