Abstract: This work aimed to study the antimicrobial resistance, key virulence genes and genetic evolution of Vibrio parahaemolyticus isolated from aquatic products imported to Shanghai for the purpose of providing supportive data for the early warning of V. parahaemolyticus contamination risks and tracking its sources. A total of 68 isolates were obtained from aquatic products imported to Shanghai in the years between 2017 and 2019 and analyzed for antimicrobial susceptibility, key virulence genes and multi-locus sequence typing. These isolates showed the highest resistance rate to ampicillin (98.53%), whereas their resistance rates to other antimicrobials tested were relatively lower, and all the isolates were sensitive to levofloxacin and chloramphenicol. Intermediate resistance was observed for nine antimicrobials, among which, the intermediate resistance rates to aminoglycosides, piperacillin, ciprofloxacin and cefoxitin were relatively higher. In total, 20.59% of the isolates were resistant to two or more antimicrobials. One isolate was found to harbor trh, and no isolate harbored tdh. A total of 65 sequence types (STs) were identified, of which, 52 were novel STs. No apparent correlation was found between geographical origin, food type and ST type; however, isolates of the same specific STs were identified in the same type of food samples imported from the same country at different times. In conclusion, the V. parahaemolyticus isolates were highly genetically diverse and showed intermediate resistance and multiple resistance to drugs, and some of them were found to have high pathogenic potential. Thus, much attention should be paid to this issue.

Key words: Vibrio parahaemolyticus; multi-locus sequence typing analysis; virulence gene; antimicrobial resistance