Presence of pathogenic Vibrio parahaemolyticus strains in mussels from the Adriatic Sea, Italy

Samples of mussels (Mytilus galloprovincialis) collected from approved coastal sites located on the Adriatic Sea (Central Italy) were examined for the presence of Vibrio parahaemolyticus and the occurrence of pathogenic strains. The isolation of the micro-organisms was performed using a standard method. A biochemical protocol was applied for the identification of the isolates. Polymerase chain reaction (PCR) was used to confirm the identification of the strains and to detect the tdh and trh genes. The Kanagawa phenomenon was assayed as phenotypic marker of thermostable direct hemolysin (TDH) toxin. The urease activity was assayed as phenotypic marker of trh gene. The protease activity and the cytotoxicity of strains were examined to identify other potential virulence factors. Thirty-five V. parahaemolyticus strains were isolated out of 144 samples. The tdh and trh genes were in one and three isolates, respectively. All strains, independent of the presence of tdh and trh genes, showed protease activity and cytotoxicity. Due to the occurrence of pathogenic V. parahaemolyticus, the potential risk of eating raw or undercooked mussels is envisaged.