[Detection of Salmonella, Listeria spp., Vibrio spp., and Yersinia enterocolitica in frozen seafood and comparison with enumeration for faecal indicators: implication for public health].

Infections transmitted through consumption of contaminated seafood is a significant source of human morbidity. The aim of this study was to compare the detection of Salmonella, Listeria, Vibrio, and Yersinia enterocolitica in frozen seafood with results from enumeration of conventional faecal indicators. A total of 213 crustaceans or molluscs were purchased from local vendors in Italy: 74% were harvested in Italy, 25% from other European countries and 1% from outside Europe. Listeria spp. was isolated from 20% of samples, Vibrio spp. from 11%, Salmonella from 3% and Y. enterocolitica from 1%. Listeria species isolated were L. monocytogenes, L. innocua, L. welshimeri, L. ivanovii and L. seeligeri. Vibrio species isolated were V. alginolyticus and V. fluvialis. The most contaminated shellfish for both faecal indicator microrganism and pathogens were hen clams (6% contained Salmonella, 27% Listeria spp. and 3% Y. enterocolitica), while from 27% of shrimps Vibrio spp. was recovered. Higher levels of faecal indicators were recovered from samples harvested outside Europe, and 66% of samples harvested in Thailand were contaminated from Salmonella. Significant differences were found in the levels of contamination of seafoods depending upon the freezing regime, but there was a limited association between presence of potential pathogens (particularly Vibrio spp.) and conventional faecal indicators. Hence, we suggest reconsideration of current legal parameters to evaluate microbiological quality of seafood.