Vibrio mediterranei, a potential emerging pathogen of marine fauna: investigation of pathogenicity using a bacterial challenge inPinna nobilisand development of a species-specific PCR

Aims Extreme mortality events affectingPinna nobilis, some associated toVibrio mediterranei,have depleted many populations of this bivalve. The objective of this study was to demonstrate pathogenicity ofV. mediterraneiin the hostP. nobilisby performing a bacterial challenge inP. nobilisto understand ifV. mediterraneihas specific virulence in this host. To assist this objective, a secondary objective was to develop a species-specific DNA diagnostic test. Methods and Results Pinna nobiliscollected from local bays were used in a challenge experiment withV. mediterranei(strain IRTA18-108). The virulence in the host background ofP. nobiliswas demonstrated at doses of 10(3)CFUs per animal. An alignment of publishedVibriosp.atpAsequences was used to designV. mediterranei-specific primers. Furthermore, data mining of published literature andV. mediterraneigenomes identified multiple virulence-related genes (virgenes) from which specific primers were designed for PCR detection of selected genes. Conclusion Vibrio mediterraneistrain IRTA18-108 is pathogenic in the hostP. nobilis. The virulence genessod, rtxandmshAwere identified in this strain. Temperatures of 24 degrees C 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.