Vibrio mediterranei, a Potential Emerging Pathogen of Marine Fauna: Investigation of pathogenicity using a bacterial challenge in Pinna nobilis and development of a species‐specific PCR

Abstract

Aims Extreme mortality events affecting Pinna nobilis, some associated to Vibrio mediterranei, have depleted many populations of this bivalve. The objective of this study was to demonstrate pathogenicity of V. mediterranei in the host P. nobilis by performing a bacterial challenge in P. nobilis to understand if V. mediterranei has specific virulence in this host. To assist this objective, a secondary objective was to develop a species‐specific DNA diagnostic test.

Methods and Results P. nobilis collected from local bays were used in a challenge experiment with V. mediterranei (strain IRTA18‐108). Virulence in the host background of P. nobilis was demonstrated at doses of 103 CFUs / animal.

An alignment of published Vibrio spp. atpA sequences was used to design V. mediterranei ‐specific primers. Further, data mining of published literature and V. mediterranei genomes identified multiple virulence‐related genes (vir genes) from which specific primers were designed for PCR detection of selected genes.

Conclusion V. mediterranei strain IRTA18‐108 is pathogenic in the host P. nobilis . The virulence genes sod, rtx , and mshA were identified in this strain. Temperatures of 24ºC or higher appear to trigger onset of virulence. Sensitivity and specificity of the Vm atpA PCR is useful for diagnosis of Vibriosis in shellfish.

Significance and Impact of the Study The presence of previously described virulence genes have been confirmed in this strain. The specific Vm atpA PCR assay will aid management of future epizootics of this emerging pathogen of aquatic fauna, and improve surveillance capabilities for mortality events where Vibrios are suspect.