ANTIGENIC CHARACTERIZATION OF VIBRIO ANGUILLARUM-RELATED ORGANISMS ISOLATED FROM TURBOT AND COD

This work reports on the antigenic characterization and virulence for rainbow trout Oncorhynchus mykiss of Vibrio anguillarum-related (VAR) strains isolated from diseased turbot Scophthalmus maximus and cod Gad us morhua in Spain and Denmark. These vibrio strains belong to Vibrio splendidus biovar I (serogroups B, C, D, F and G) and V. pelagius biov ar I (serogroup A). The pathogenicity assays demonstrated that 10 of 1 5 (67%) VAR strains tested were virulent for rainbow trout, showing an LD(50) (50% lethal dose) ranging from 8.4 x 10(3) to 7 x 10(5) CFU (c olony forming units) per fish. Moreover, all the V. splendidus biovar I strains of serogroup F, which is the predominant type among strains isolated from cod, were virulent for rainbow trout, while V. splendidu s biovar I strains isolated from turbot were avirulent. Analysis of li popolysaccharides (LPS) and membrane proteins showed that VAR strains belonging to different serogroups possessed distinct electrophoretic b anding patterns. The immunoblot analysis demonstrated a high immunorel ation among VAR strains of the same serogroups, while strains from dif ferent serogroups were not immunologically related. Immunoblot assays also confirmed the dissimilarities in LPS structure observed among the distinct subgroups of serogroup F. These findings suggest that presen t vibriosis vaccines for cod could be improved if V. splendidus biovar I representative of serogroup F (subgroups alpha and beta) were teste d in trial vaccines.