Investigation of host–microbe interactions between mussels and Vibrio parahaemolyticus or Salmonella Napoli

Bivalves are filter-feeding animals capable to accumulate human pathogenic microorganisms. Vibrio parahaemolyticus and Salmonella enterica are food-borne pathogens that could be transmitted through consumption of raw or... [ view full abstract ]

Bivalves are filter-feeding animals capable to accumulate human pathogenic microorganisms. Vibrio parahaemolyticus and Salmonella enterica are food-borne pathogens that could be transmitted through consumption of raw or undercooked bivalves. Longer depuration times in respect to E. coli or resistance to depuration have been reported for Salmonella or Vibrio in bivalves. This work aimed to investigate host–microbe interactions between Salmonella or V. parahaemolyticus and mussels (Mytilus galloprovincialis). Mussels were bioaccumulated with a tdh-/trh+ or tdh-/trh- V. parahaemolyticus or S. Napoli isolate. Bacterial levels, immunohistochemistry (IHC) and/or histology were performed every 24 until 96h from test groups and negative controls. All groups exposed to toxigenic V.parahaemolyticus strain showed the same inflammatory lesions detected in mussels exposed to S. Napoli. The non toxigenic strain only determined a moderate infiltration of connective tissue and atrophy of digestive gland epithelium. All groups exposed to S. Napoli showed ulceration of the gastric mucosal layer, cell vacuolation and connective tissue haemocytic infiltration. Bacterial clusters were detected by IHC in mantle, digestive tract, haemocytes and gonadic tissue. The observed intrahaemocytic positivity could suggest survival of S. Napoli within these cells and potential diffusion in mussels. The same bacterial tissue localization reported by a previous work in oysters was observed in mussels. Further experiments are currently performed to investigate the host-microbe interactions in a depuration system. Moreover, experiments with mussels exposed to other toxigenic or non-toxigenic strains of V. parahaemolyticus are needed to investigate if these effects are strain-related.