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 pre-processing and processing stages, as there is no bactericidal process involved to eliminate any pathogen during the processing of cold-smoked salmon.
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