Comparative Serology of the Marine Fish Pathogen Vibrio anguillarum

The different serotyping systems, based on thermostable O antigens, reported for Vibrio anguillarum and V. ordalii were compared by quantitative agglutination, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and subsequent silver staining or Western blotting (immunoblotting) of purified lipopolysaccharide (LPS), using polyclonal rabbit antisera. The results demonstrate that 16 different serotypes within V. anguillarum (designated O1 to O16) can be distinguished. Each of these serotypes is characterized by a distinct polysaccharide banding pattern, as revealed by silver-stained gels of purified LPS. The comparative analysis allowed a complete alignment of the different serotypes for the first three serovars: O1, O2, and O3. Moreover, immunoblotting showed that strains belonging to each of these serotypes had the same LPS banding pattern independent of the origin of the strain. Serotype O2 contains different subtypes, O2a and O2b. While no differences were apparent between these subgroups in silver-stained gels, they could be separated by quantitative agglutination (titer determination) or immunoblotting. V. ordalii, the former biotype II of V. anguillarum, strongly reacts with anti-V. anguillarum O2a antiserum. Strains of the two species can be separated on the basis of different LPS profiles in the high-molecular-weight region of silver-stained gels of purified LPS. The silver-stained LPS profiles of the different serotypes of V. anguillarum that have been established are provided for further comparison in the future.