| Summary: | The majority (91%) of 260 isolates initially identified as Vibrio anguillarum , that were obtained from a wide range of hosts, habitats and geographical locations, were recovered in a single cluster based on the ribotype and were pathogenic to Atlantic salmon. A significant proportion of isolates (78% of the total) were allocated to 15 serogroups (O1–O10 and five previously undescribed groups referred to as VaNT1, VaNT2, VaNT4, NaNT5 and VaNT7). A minority of isolates (6%) reacted with more than one antiserum or were self-agglutinating, and the remainder did not react with any of the antisera tested. Good correlation was noted between serogroups and lipopolysaccharide profiles, particularly with respect to isolates belonging to serogroups O1, 02 and 04ߝ010. Plasmids were recognized in some serogroups. especially O1, which contained the 67 kb plasmid associated with virulence. However, the 19 profiles based on outer membrane protein patterns did not correspond to the results obtained with the other typing methods. Generally, the isolates were heterogeneous in their biochemical characteristics; 117 profiles were obtained with the API 20E system, and 9 and 32 clusters recognised from the results of BIOLOG fingerprinting and Biotype-100 biotyping methods, respectively. Three dominant dusters were defined from fatty acid methyl esters profiles.
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