Sodium Ascorbate as a Quorum-Sensing Inhibitor Leads to Decreased Virulence in Vibrio campbellii

Vibrio campbelliiis one of the major bacterial pathogens for animals reared in aquaculture, affecting both vertebrates and invertebrates, and causes significant economic losses. It is now evident that the expressions of virulence factors in this pathogen are regulated by the density of the bacterial population. This type of regulation, termed quorum sensing (QS), is mediated by extracellular signal molecules called autoinducers. In this study, the impact of sodium ascorbate (NaAs) on the virulence ofV. campbelliiwas investigated under bothin vitroandin vivoconditions, to develop a natural anti-infective strategy to containV. campbelliiinfection in aquacultured animals. Results showed that NaAs significantly decreased swimming motility, biofilm production, and the production of virulence enzymes, such as lipase, caseinase, phospholipase, and hemolysin inV. campbellii. Consistent with this, pretreatment ofV. campbelliiwith NaAs before inoculation into the rearing water resulted in significantly increased survival of gnotobiotic brine shrimp larvae, when compared to larvae challenged with untreatedV. campbellii. Furthermore, NaAs could interfere with QS-regulated bioluminescence inV. campbellii, suggesting the QS-inhibitory activity largely determines the protective effect of NaAs toward the brine shrimp. In essence, due to the potent anti-virulence effects observed inin vitrostudies and the clinical brine shrimp-V. campbelliiinfection model, NaAs constitute a promising novel strategy for the control ofV. campbelliiinfections in aquaculture.