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

Biao Han,Peter Bossier,Kartik Baruah,Xiaoting Zheng

doi:10.3389/fmicb.2020.01054

Abstract

Vibrio campbellii is 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 of V. campbellii was investigated under both in vitro and in vivo conditions, to develop a natural anti-infective strategy to contain V. campbellii infection 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 in V. campbellii. Consistent with this, pretreatment of V. campbellii with NaAs before inoculation into the rearing water resulted in significantly increased survival of gnotobiotic brine shrimp larvae, when compared to larvae challenged with untreated V. campbellii. Furthermore, NaAs could interfere with QS-regulated bioluminescence in V. 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 in in vitro studies and the clinical brine shrimp-V. campbellii infection model, NaAs constitute a promising novel strategy for the control of V. campbellii infections in aquaculture.

Highlights

Vibrio campbellii is a Gram-negative luminous bacterium that lives in a broad range of aquatic environments
This study aimed at investigating the effect of NaAs on the virulence of V. campbellii in vitro and in vivo in a highly controlled model system with gnotobiotic brine shrimp (Artemia franciscana) larvae, and the results of this study could provide a novel strategy for the control of V. campbellii infections in aquaculture
The results from the present study demonstrated that NaAs could decrease the virulence of V. campbellii toward the brine shrimp host, as manifested by higher survival of brine shrimp larvae exposed to the pathogen pre-treated with NaAs at either 5 or 10 mg ml−1 concentration (Table 3)

Summary

Introduction

Vibrio campbellii is a Gram-negative luminous bacterium that lives in a broad range of aquatic environments. It has been regarded as a serious pathogen affecting numerous vertebrates and invertebrates, which leads to significant losses to the aquaculture industry (Defoirdt et al, 2008; Yang et al, 2015). The infectious steps of bacterial pathogens include adhesion and incubation in the host, avoidance of host defenses, causing diseases and mortality, and exit (Donnenberg, 2000). These steps involve the expression of virulence factors that allow the Ascorbate Interferes the Quorum Sensing pathogens to infect and damage the host. For Vibrio campbellii, the ability to adhere to host surface and form biofilms, produce extracellular products (E) and lipopolysaccharide (LPS), and interact with bacteriophage and bacteriocin-like substance (BLIS) are its most crucial virulence determinants (Austin and Zhang, 2006; Darshanee Ruwandeepika et al, 2012)

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