Classification of Pasteurella field strains isolated from farms in Germany using traditional methods and DNA-DNA...

410 Pasteurella (P.) field strains isolated from calves and piglets were classified according to Bisgaard et al. (1). 376 strains were assigned to P. multocida ssp. multocida, 34 of them were ornithine- and trehalose+, and 61 of them ornithine- and trehalose-. 4 strains belonged to P. multocida ssp. septica, 4 to P. multocida ssp. gallicida, 6 to P. avium biovar 2 and 20 to P. canis biovar 2. There was no difference in the prevalence of the species in calves and pigs. The fact that strains belonging to P. multocida ssp. septica were isolated only from calves and P. multocida ssp. multocida ornithine- and trehalose- were mostly isolated from piglets could indicate a certain host specificity of these isolates. In genotypic investigations 20 field isolates of P. multocida belonging to different Carter serotypes, as well as serologically negative strains were compared to reference strains in terms of deoxyribonucleic acid (DNA) relatedness. The data obtained by filter hybridization revealed a considerable degree of genotypic intraspecies heterogeneity within P. multocida. No correlations to the respective serotypic classification could be detected.