Prevalence, antimicrobial resistance and genetic characterization of Vibrio parahaemolyticus isolated from retail aquatic products in Nanjing, China

Vibrio parahaemolyticus, is one of the most frequently reported pathogenic microorganisms that causes foodborne illnesses worldwide. The aims of the current study were to determine the prevalence, virulence genes, antimicrobial resistance, biofilm formation ability (BFA) and genetic characterization of V. parahaemolyticus recovered from retail aquatic products in Nanjing, China. There were 131 samples (71.6%) that tested positive for V. parahaemolyticus. The thermostable direct hemolysin-related hemolysin (trh) gene was found in two isolates (1.5%). Antimicrobial susceptibility tests showed that 46.6% of isolates were multidrug resistant. High resistance was observed to ampicillin (100%), cephalosporin (99.2%), trimethoprim/sulfamethoxazole (38.2%) and tetracycline (16.0%). Ten resistance patterns were found. The crystal violet staining assay showed that 35.1% had strong BFA, and 52.7% had intermediate BFA; notably, five (3.8%) extremely strong BFA strains were obtained from wet markets. According to whole genome sequencing analysis of 59 randomly selected isolates, 46 sequence types (STs) were identified, including 22 novel STs, and ST1042 was the dominant sequence type. It is clear that the V. parahaemolyticus population exhibits a high level of genetic variation. Our findings provide comprehensive insight into the prevalence and phylogenetic relationship of V. parahaemolyticus in aquatic products, suggesting potential hazards to consumers in Nanjing.