Does Virulence Assessment of <i>Vibrio anguillarum</i> Using Sea Bass (<i>Dicentrarchus labrax</i>) Larvae Correspond with Genotypic and Phenotypic Characterization?

Abstract

<div><p>Background</p><p>Vibriosis is one of the most ubiquitous fish diseases caused by bacteria belonging to the genus <i>Vibrio</i> such as <i>Vibrio (Listonella) anguillarum</i>. Despite a lot of research efforts, the virulence factors and mechanism of <i>V. anguillarum</i> are still insufficiently known, in part because of the lack of standardized virulence assays.</p><p>Methodology/Principal Findings</p><p>We investigated and compared the virulence of 15 <i>V. anguillarum</i> strains obtained from different hosts or non-host niches using a standardized gnotobiotic bioassay with European sea bass (<i>Dicentrarchus</i> labrax L.) larvae as model hosts. In addition, to assess potential relationships between virulence and genotypic and phenotypic characteristics, the strains were characterized by random amplified polymorphic DNA (RAPD) and repetitive extragenic palindromic PCR (rep-PCR) analyses, as well as by phenotypic analyses using Biolog’s Phenotype MicroArray™ technology and some virulence factor assays.</p><p>Conclusions/Significance</p><p>Virulence testing revealed ten virulent and five avirulent strains. While some relation could be established between serotype, genotype and phenotype, no relation was found between virulence and genotypic or phenotypic characteristics, illustrating the complexity of <i>V. anguillarum</i> virulence. Moreover, the standardized gnotobiotic system used in this study has proven its strength as a model to assess and compare the virulence of different <i>V. anguillarum</i> strains <i>in vivo</i>. In this way, the bioassay contributes to the study of mechanisms underlying virulence in <i>V. anguillarum</i>.</p></div