Molecular Characterization and Phenotyping of Pasteurella from Swiss Rabbits

Several bacteria belonging to the family Pasteurellaceae might act as pathogens in rabbits. In particular, Pasteurella multocida is considered to be an important one and outbreaks caused by this species result in considerable economic losses. However, proper identification of P. multocida at the species and even more so at the subspecies level is often not very precise. Moreover, Pasteurellaceae species isolated from rabbits are poorly characterized. We therefore phenotypically and genotypically analyzed 228 isolates from different rabbit populations including a breeding and fattening organization with group management as well as isolates from single post-mortem cases with pasteurellosis using biochemical reactions and repetitive extragenic palindromic (REP)-PCR. Furthermore, 41 samples were selected for phylogenetic analysis of 16S rRNA gene. REP-PCR identification and phylogenetic analyses correlated well and appeared to be distinct molecular methods for identification of rabbit isolates. Phenotyping, however, diverged from molecular recognition, indicating the problematic conventional diagnosis of these strains. The fermentation of sorbitol and trehalose appeared to be imprecise indicators for P. multocida subspecies classification. However, according to REP-PCR and sequencing results, 82% of the isolates were characterized as P. multocida ssp. multocida, 3% as P. multocida ssp. septica, 5% could be assigned to P. multocida and probably represented a new subspecies within this species. Further, 5% were assigned to Pasteurella canis. The other 5% represented a homogeneous group of unknown species belonged to the Pasteurellaceae. Samples obtained from post-mortem cases demonstrated a higher phenotypic and genetic heterogeneity than samples from group management rabbits.