Prevalence and antimicrobial susceptibility of Vibrio parahaemolyticus isolated from retail shellfish in Shanghai

Vibrio parahaemolyticus is a marine and estuarine bacterium that poses the greatest threat to human health worldwide. It has been the leading bacterial cause of seafood-borne illness. This study investigated the prevalence and drug resistance of V. parahaemolyticus isolated from retail shellfish in Shanghai. A total of 140 shellfish samples were collected from February 2014 to February 2015. The occurrence of V. parahaemolyticus in shellfish was 34.3%, which has increased compared to previous reports. In addition, discernible differences of total presumptive V. parahaemolyticus counts (TPVPC) were also observed in shellfish between market A and B. The results from PCR assays indicated that thermostable direct hemolysin (tdh) gene was positive in two isolates (2.1%), and the thermostable direct hemolysin-related hemolysin (trh) gene was not detected in all isolates. Antibiotic resistance profiles of those isolates were as follows: ampicillin (87.5%), cephazolin (31.3%), cephalothin (6.3%), amoxicillin/clavulanic acid (6.3%), piperacillin (6.3%), and amikacin (3.2%). Thirty-three out of 96 isolates were resistant to two or more antimicrobial agents. It is suggested that V. parahaemolyticus in retail shellfish could be a potential risk to consumers in Shanghai.