Purpose: To determine the occurrence of Listeria spp., including L. monocytogenes, in a BC RTE fish processing plant and characterize recovered L. monocytogenes genetically and phenotypically.
Methods: Environmental samples (n = 1748) were collected over a one-year period from a RTE fish processing plant in BC and were subjected to Health Canada standard procedures MFHPB-29 or MFHPB-30 for detection and isolation of Listeria spp. and L. monocytogenes. L. monocytogenes isolates (n = 14) were subsequently characterized by lineage-typing ASO-PCR, assessed for frequency of mutation by plating isolates on Brain Heart Infusion Agar with rifampicin (100μg/ml), and screened by PCR for genetic markers that may contribute to increased persistence (e.g., LGI1 and bcrABC).
Results: Listeria spp. and L. monocytogenes were recovered in 2.6% and 1.0% of samples, respectively. Cutting boards and raw fish surfaces yielded 93% of the samples positive for L. monocytogenes. Lineage-typing revealed that the majority of L. monocytogenes recovered belong to Lineage I (60%), with the remainder belonging to Lineage II. The frequency of mutations between lineages was not significantly different (P = 0.07) and LGI1 and bcrABC were absent in all screened isolates.
Significance: This research provides improved understanding of Listeria spp. and L. monocytogenes prevalence in a BC RTE fish processing facility coupled with details regarding genetic and phenotypic attributes of recovered L. monocytogenes. This knowledge will help processors tailor their L. monocytogenes control strategies to minimize contamination of products entering the food chain.