Characterization of Pasteurella Hemolytica Isolated from the Respiratory Tract of Cattle

Morphological, cultural, biochemical, and serological characteristics of 43 strains of Pasteurella hemolytica isolated from the respiratory tract of cattle, including 37 that had shipping fever, were determined. With one exception, all strains satisfied the major criteria for differentiation of the species from P. multocida — hemolysis on blood agar, absence of indole production, and growth on MacConkey's agar. Many strain variations in fermentative capacity were noted, although other biochemical characteristics were relatively constant. The ability of a strain to ferment carbohydrates often depended upon the medium in which the test was conducted. All strains studied were identified as type A strains on the basis of colonial morphology, biochemical, and growth characteristics, and sensitivity to penicillin. When grouped on the basis of serological reactions, 38 strains were type 1, three were type 2, one was type 11, and one was untypable; 34 of the shipping fever strains were 1 and three were type 2.