Comparative analysis of Pasteurella pneumotropica isolates from laboratory mice and rats.

Selected biochemical and genetic characteristics of the wild-type strains of Pasteurella pneumotropica isolated from mice and rats were investigated and compared in order to determine the significant differences among the isolates. The isolates were divided into six groups on the basis of the patterns of carbon source utilization in the host rodents. The genome sizes were determined by electrophoretic analysis, and the mean genome size of the isolates from mice was larger than that of the isolates from rats (P < 0.05). Cluster analysis of the rpoB sequences discriminated five clusters; the differences might have correlated with the host associations. Principal component analysis (PCA) based on both the biochemical and genetic characteristics revealed total 44 strains discriminated into three groups comprising the host-dependent and host-independent groups. Although the P. pneumotropica isolates were mainly classified on the basis of the host rodents by the examinations, the existence of isolates that could not be discriminated on the basis of the host rodents alone was confirmed by the PCA. These results indicated that the P. pneumotropica isolates could be further classified by taxonomic analysis and also suggested the existence of a host-independent group in addition to the host-dependent groups.