Blueberry extract inhibits quorum-sensing regulators and controls Vibrio parahaemolyticus biofilms and virulence

Anti-biofilm and anti-virulence effects of blueberry extract (BE) at sub-inhibitory of concentrations (SICs) against Vibrio parahaemolyticus were investigated in this study. When three V. parahaemolyticus strains were exposed to BE at 6.25 mg/mL and 9.38 mg/mL, swarming and twitching motility were suppressed by 40.4%-57.1% and 20.8%-39.1%, respectively. Hydrophobicity and auto-aggregation were decreased by 63.2%-94.5% and 43.8%- 88.4%, respectively. The decrease in AI-2 production ranged from 24.8% to 76.8%. The biofilm formation index remained less than 0.64 after 24-72h incubation. Microscopic analyses further evidenced that the dense and thick biofilm architecture were significantly weaken. Meanwhile, BE differentially repressed the expression of the critical genes involved in flagellum (mshA), pili (oxyR), QS (aphA, opaR, and luxS), EPS (cpsA and cpsF), and T3SS (vcrD1, vopD1, and vopS). These results suggested that BE could suppress the motility and cellular surface properties by controlling QS regulators, which further inhibited biofilm formation of V. parahaemolyticus. Thus, BE may be a new alternative natural antibiofilm agent in the future.