A group of indole-negative bovine strains with high deoxyribonucleic acid homology to Pasteurella multocida.

A group of nine bovine Pasteurella strains not producing indole were investigated for their taxonomic relationships with Pasteurella multocida, Pasteurella haemolytica and Pasteurella canis. For all strains, DNA-DNA hybridization has revealed a high genetic relatedness at the species level to P. multocida and significantly lower homologies of only 18-41% towards P. haemolytica and 11-15% towards P. canis. Guanine plus cytosine values of 38.0 to 42.1 mol% and several phenotypic characters have been found to be different from the established pattern for P. multocida subspecies. It is suggested that the strains represent a new taxon, possibly another P. multocida subspecies.