Yersinia ruckeri biotype 2 isolates from mainland Europe and the UK likely represent different clonal groups.

There have been increased reports of outbreaks of enteric redmouth disease (ERM) caused by Yersinia ruckeri in previously vaccinated salmonids in Europe, with some of these outbreaks being attributed to emergent non-motile, Tween 80-negative, biotype 2 isolates. To gain information about their likely origins and relationships, a geographically and temporally diverse collection of isolates were characterised by serotyping, biotyping, pulsed-field gel electrophoresis (PFGE) and outer membrane protein (OMP) profiling. A total of 44 pulsotypes were identified from 160 isolates by PFGE, using the restriction enzyme NotI.