Genomic and Transcriptomic Analysis Reveal Multiple Strategies for the Cadmium Tolerance in Vibrio parahaemolyticus N10-18 Isolated from Aquatic Animal Ostrea gigas Thunberg.

The waterborne Vibrio parahaemolyticus can cause acute gastroenteritis, wound infection, and septicemia in humans. Pollution of heavy metals in aquatic environments is proposed to link high incidence of the multidrug-resistant (MDR) pathogen. Nevertheless, the genome evolution and heavy metal tolerance mechanism of V. parahaemolyticus in aquatic animals remain to be largely unveiled. Here, we overcome the limitation by characterizing an MDR V. parahaemolyticus N10-18 isolate with high cadmium (Cd) tolerance using genomic and transcriptomic techniques. The draft genome sequence (4,910,080 bp) of V. parahaemolyticus N10-18 recovered from Ostrea gigas Thunberg was determined, and 722 of 4653 predicted genes had unknown function. Comparative genomic analysis revealed mobile genetic elements (n = 11) and heavy metal and antibiotic-resistance genes (n = 38 and 7). The bacterium significantly changed cell membrane structure to resist the Cd2+ (50 µg/mL) stress (p < 0.05). Comparative transcriptomic analysis revealed seven significantly altered metabolic pathways elicited by the stress. The zinc/Cd/mercury/lead transportation and efflux and the zinc ATP-binding cassette (ABC) transportation were greatly enhanced; metal and iron ABC transportation and thiamine metabolism were also up-regulated; conversely, propanoate metabolism and ribose and maltose ABC transportation were inhibited (p < 0.05). The results of this study demonstrate multiple strategies for the Cd tolerance in V. parahaemolyticus.

Virulence, resistance, and genetic diversity of Vibrio parahaemolyticus recovered from commonly consumed aquatic products in Shanghai, China.

Vibrio parahaemolyticus can cause severe gastroenteritis, septicaemia and even death in humans. Continuous monitoring of V. parahaemolyticus contamination in aquatic products is imperative for ensuring food safety. In this study, we isolated and characterized 561 V. parahaemolyticus strains recovered from 23 species of commonly consumed shellfish, crustaceans, and fish collected in July and August of 2017 in Shanghai, China. The bacterium was not isolated from two fish species Carassius auratus and Parabramis pekinensis. The results revealed a very low occurrence of pathogenic V. parahaemolyticus carrying the toxin genes trh (0.2%) and tdh (0.0%). However, high percentages of resistance to the antimicrobial agents ampicillin (93.0%), rifampin (82.9%), streptomycin (75.4%) and kanamycin (50.1%) were found. A high incidence of tolerance to the heavy metals Hg2+ (74.7%) and Zn2+ (56.2%) was also observed in the isolates. ERIC-PCR-based fingerprinting of MDR isolates (77.5%) revealed 428 ERIC-genotypes, demonstrating remarkable genetic variation among the isolates. The results of this study support the urgent need for food safety risk assessment of aquatic products.