PLASMID PROFILES, RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISMS AND O-SEROTYPES AMONG VIBRIO-ANGUILLARUM ISOLATES

A total of 279 Vibrio anguillarum strains were serotyped and examined for plasmid content. Plasmids were subjected to digestion with restric tion enzymes. Most strains belonged to serogroup O1 (39%) and O2 (16%) . In total 164 strains (53%) carried plasmids. Of the O1 and O2 isolat es, 92% and 30%, respectively, carried one or more plasmids. Restricti on fragment length polymorphism (RFLP) analysis of plasmid DNA indicat ed that plasmids belonged to several groups. Each group seemed to be r estricted to a single O-serovar. The largest group was the pJM1-like p lasmids among most serovar O1 strains. Most of these plasmids were abo ut 67 kb like the pJM1 plasmid, but various derivatives ranged from 26 -77 kb. RFLP studies of the 67 kb plasmids revealed 17 different restr iction patterns. Some patterns were dominant among European strains wh ereas others were dominant among North American strains. The results c onfirmed the applicability of O-serotyping together with plasmid profi le and restriction analysis of plasmids for typing of V. anguillarum. They also indicated that plasmids among strains which belonged to the traditional fish pathogenic serogroups, O1 and O2, showed more homolog y than did strains from most other serogroups, that were usually non-p athogenic, environmental bacteria.