ABSTRACT: 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 Gadus morhua in Spain and Denmark. These vibrio strains belong to Vibrio splendidus biovar I (serogroups B, C, D, F and G) and V. pelagius biovar I (serogroup A). The pathogenicity assays demonstrated that 10 of 15 (67%) VAR strains tested were virulent for rainbow trout, showing an LD₅₀ (50% lethal dose) ranging from 8.4 [lozenge] 10³ to 7 [lozenge] 10⁵ CFU (colony 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. splendidus biovar I strains isolated from turbot were avirulent. Analysis of lipopolysaccharides (LPS) and membrane proteins showed that VAR strains belonging to different serogroups possessed distinct electrophoretic banding patterns. The immunoblot analysis demonstrated a high immunorelation among VAR strains of the same serogroups, while strains from different 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 present vibriosis vaccines for cod could be improved if V. splendidus biovar I representative of serogroup F (subgroups alpha and beta) were tested in trial vaccines.

KEY WORDS: Vibro anguillarum-related organisms · Turbot · Cod · LPS · Proteins · Virulence

Published in DAO Vol. 28, No. 1 (1997) on January 16
ISSN: 0177-5103. Copyright © Inter-Research, Oldendorf/Luhe, 1997