Pathogenicity of Vibrio splendidus strains associated with turbot larvae, Scophthalmus maximus

Turbot larvae were challenged with eight strains of Vibrio splendidus isola ted from diseased larvae, plus a ninth strain pathogenic to scallop larvae (A515; Nicolas et al. 1996). Six strains caused heavy mortality but the sca llop pathogen and the other two strains did not. All the strains shared a l arge number of phenotypic traits, and an attempt was made to relate virulen ce to genotype and phenotype. Five of the six pathogenic strains were very similar, as shown by RAPD fingerprinting and phenotypic characteristics. Th e relatedness of the other strains was intermediate between the main pathog enic group and V. splendidus ATCC 33125, but the DNA-DNA homology between t he pathogenic group and the reference strain was still high (78% of reassoc iation rate). The non-pathogenic isolates may be a useful tool for determin ing the possible virulence factors, as all the isolates differed by few cha racteristics.