Taxonomic relationship of selected biogroups of Pasteurella haemolytica as revealed by DNA:DNA hybridizations.

Genetic investigations of selected bovine and ovine strains of Pasteurella haemolytica sensu stricto (biogroup 1), P. haemolytica biogroups 2, 3, 5 and 9, P. testudinis and porcine isolates of so-called P. haemolytica, tentatively designated taxon 15, confirmed the existence of these phenotypically delineated taxa. Evidence was further obtained to indicate that P. haemolytica biogroups 1, 2, 3, 5 and 9 and P. testudinis constitute a new genus within the family Pasteurellaceae Pohl 1981, and that P. testudinis represents a "missing link" between so-called P. haemolytica biovars A and T. The proposed genus seems to contain several new species. Additional investigations are, however, indicated before final conclusions can be drawn. The authors desist from proposing genus and species names for the same reasons. Porcine strains provisionally named taxon 15 seem to constitute a separate group within the family Pasteurellaceae Pohl 1981, underlining the distinct degree of specificity members of this family show for host species.