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Objective: Food phytochemicals as biofilm inhibitor of pathogens have been highlighted. Our study aimed to investigate the effects of resveratrol on biofilm formation of an aquatic pathogen Vibrio parahaemolyticus, and to elucidate the important regulatory genes., Methods: In the subinhibitory concentrations, the inhibition of resveratrol aganist biofilm and exopolysaccharides of V. parahaemolyticus was detected, and the differentially expressed genes were analyzed based on RNA-Seq. Four genes involved in biofilm formation was validated by qRT-PCR., Results: The minimum inhibitory concentration of resveratrol against V. parahaemolyticus was 20 μg/mL. Resveratrol at the subinhibitory concentration of 5 μg/mL and 10 μg/mL significantly decreased the biofilm development and exopolysaccharides production in V. parahaemolyticus (P < 0.05). Scanning electron microscopy micrographs showed a significant reduction of adherence and extracellular polymeric substances. RNA-Seq analysis revealed that 22.6% up-regulated and 77.4% down-regulated gene (P < 0.05) after treatment by 10 μg/mL resveratrol among 106 differential gene expressions. These differential genes in V. parahaemolyticu focused on 7 metabolic pathways, and 14 genes involved in biofilm formation were down-regulated by resveratrol, such as outer membrane protein (W, YedS, OmpK), quorum sensing (LuxS), flagellin (FlaA), fimbrial assembly protein (PilQ), hemolysin secreted protein. qRT-PCR confirmed that the expressions of luxS, trh, tlh and flaA, was significantly repressed in the presence of resveratrol, which was consistent with transcriptomics data., Conclusion: Inhibitory activity of resveratrol on biofilm formation was assicated with multiple genes and diverse cellular processes in V. parahaemolyticus. These findings suggest that resveratrol would disturb various metabolic pathways, particularly quorum sensing system, adhesion process and membrane proteins secretion, resulting in inhibition of attachment and biofilm development. The present work provided valuable information to explore molecular mechanism of resveratrol as an novel anti-biofilm compound.

Objective: To establish the kinetic inactivation models of Vibrio parahaemolytius in saline and peeled shrimp treated with acetic acid, lactic acid and citric acid for guidance of their potential application in shrimp decontamination., Methods: To determine the survival rate (P) of V. parahaemolyticus in saline and peeled shrimp treated with organic acids, dose-response in peeled shrimp between P and concentrations of organic acids was modeled directly. Logit (P) was transformed from survival P with the formula ln [P/(1-P)] for linear modeling. Both linear models were used to interpolate 50% and 90% effective inhibitory concentrations (EC50 and EC90), which were then used to compare the difference of inhibitory potency between saline and peeled shrimp., Results: Organic acids in saline were more inhibitory to V. parahaemolyticus in saline than in peeled shrimp, seen as 160 to 200-fold increase of EC50 and EC90 for lactic acid and citric acid, and more than 70-fold increase for acetic acid. These results indicate that food matrix had significant impact on the antimicrobial activity of organic acids. We also found that EC90 of the tested organic acids in peeled shrimp was far below the 2.5% limit for use as food ingredients regulated by USDA. With equimolar concentration in the test solutions, the order of inhibitory potency is citric acid > lactic acid > acetic acid., Conclusion: Food matrix could have negative impact on antimicrobial activity of organic acids. Concentrations of organic acids around 2% could lead to significant reduction of V. parahaemolyticus contamination of peeled shrimp for improved food safety.

Objective: We developed and evaluated a whole-genome DNA microarray of Vibrio parahaemolyticus., Methods: Based on the genomic sequences of V. parahaemolyticus, we chose a total number of 4770 genes, amplified them by PCR with specific primers, purified the PCR products and printed them onto glass slides. We performed two sets of hybridizations by the method of two-fluorescence comparative hybridization to evaluate the microarray quality, followed by PCR method to validate parts of microarray results., Results: Microarray hybridization results were completely consistent with theory expectations and PCR verification results., Conclusion: We successfully developed a batch of good quality whole-genome DNA microarrays of V. parahaemolyticus, built up a method of microarray-based comparative genomic hybridization of V. parahaemolyticus and a set of microarray data analysis standard method.