Novel non-motile phenotypes of Yersinia ruckeri suggest expansion of the current clonal complex theory

Abstract

The biochemical and cell surface characteristics of 63 non-motile isolates of Yersinia ruckeri from various sources were compared using the API 20E rapid identification system and conventional phenotypic methods. Eight individual phenotypic groups were observed from the data set. All the non-motile isolates were from rainbow trout whereas novel phenotypes were observed in other fish species. Non-motile isolates were not exclusively observed from serogroup O1; membership of biotype 2 was recorded for representatives from serogroups O2 to O7. Variations in phenotypes highlights that new clonal groups are arising and that the current typing scheme requires expansion. Previously, it was hypothesised that disease was caused by a few virulent clones, data in this paper suggests that this is not the case. The lipopolysaccharide (O antigen) type in the non-motile biotype was different to other isolates of Y. ruckeri.