Occurrence of Listeria spp. in processed fishery products

Processed fishery products viz. frozen shrimps, frozen squids, frozen fish, minced meat, surimi, breaded and battered shrimps and smoked fish obtained from the seafood processing plants and fish markets located in Mangalore were investigated for the prevalence of Listeria spp. Among the 72 frozen seafood samples examined, 11.1% were found to contain Listeria spp. The incidence of Listeria spp. in shellfishes, particularly shrimps was very high (14.3%), when compared to its incidence in finfishes (4.3%). The positive isolates were Identified as L. monocytogenes and L. innocua. The incidence of Listeria was high In headless (HL) shrimps (44.4%), followed by peeled and undeveined (PUD) shrimps (23.1%). Of the 22 hot smoked fish samples consisting mainly of smoked tuna (masmin), 45.5% contained L. monocytogenes. The higher incidence of L. monocytogenes in the smoked fishery products suggested that more care had to be taken to prevent the post-process contamination in these products when compared to frozen fishery products, as otherwise these seafoods may pose a vehicle of infection to humans on consumption.