Pasteurella Caballi, a New Species from Equine Clinical Specimens

The name Pasteurella caballi is proposed for a group of organisms represented by 29 strains isolated from respiratory and other infections in horses. P. caballi strains are gram-negative, oxidase-positive, nonmotile, fermentative rods with the key characteristics of the genus Pasteurella. These strains differed from other Pasteurella species in that all were aerogenic and catalase negative, and some strains produced acid from myo-inositol and L-rhamnose. The levels of DNA relatedness of 28 P. caballi strains with labeled DNA from the proposed type strain averaged 91 and 85% (hydroxyapatite method at 55 and 70 degrees C). P. caballi was 13 to 53% related to strains representing 22 other species of the family Pasteurellaceae. The guanine-plus-cytosine content of the DNA of four strains was 41 to 42 mol%. The type strain is 83851 (=ATCC 49197).