title: Two vibrio splendidus related strains collaborate to kill Crassostrea gigas: taxonomy and host alterations.
abstract: For several years, strains phenotypically related to Vibrio splendidus have been associated with mortality outbreaks of molluscs. A former study on Crassostrea gigas demonstrated the genetic diversity of V. splendidus strains associated with diseased animals. Another study suggested that different strains may act in an additive/synergistic way leading to higher C. gigas mortality rates. Here, a strain pair (31+32) was characterised at taxonomic and virulence levels. Using a polyphasic approach, these strains were confirmed to be V. splendidus-related, without a clear discrimination between V. kanaloae and V. pomeroyi since hybridisation rates with both these strains were above 70 %. Following experimental infection of C. gigas by injection in the adductor muscle or in the pallial cavity, the host alterations induced were described. After injection of strains 31 and/or 32, bacteria were localised at the periphery of the muscle and induced extensive lesions of the translucent part of the adductor muscle. Muscle alterations were of 3 kinds: (1) presence of isolated rounded muscular fibres containing non-homogenous granular material and surrounded by a translucent halo; (2) presence of non-homogenous granular material in the cytoplasm of entire muscle bands; (3) affection of wide muscle areas with extremely condensed muscle fibres. Infiltration associated with these lesions was notably absent in the vast majority of the individuals.
authors.affiliation: Laboratoire de Génétique et Pathologie, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), 17390 La Tremblade, France.
authors.forename: Mélanie
authors.initials: M
authors.lastname: Gay
authors.forename: Tristan
authors.initials: T
authors.lastname: Renault
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Pons
authors.forename: Frédérique
authors.initials: F
authors.lastname: Le Roux
mesh_terms: D000818:Animals; D001483:Base Sequence; D016000:Cluster Analysis; D027081:DNA Gyrase / Q000235:genetics; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D009132:Muscles / Q000382:microbiology / Q000473:pathology / Q000648:ultrastructure; D009693:Nucleic Acid Hybridization; D010125:Ostreidae / Q000382:microbiology*; D010641:Phenotype; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D014733:Vibrio / Q000235:genetics* / Q000472:pathogenicity*; D014774:Virulence
chemical_list: D012336:RNA, Ribosomal, 16S; D027081:DNA Gyrase