Biochemical and serologic characterization of Klebsiella strains from bovine mastitis and the environment of the dairy cow.

Klebsiella strains isolated from the cow and its environment were biochemically and serologically characterized and evaluated for their susceptibility to normal bovine serum. Thirty-one different biotypes of Klebsiella were identified among 288 cattle and environmental strains. Of these, 56.2% were indole-positive, a greater percentage than expected for Klebsiella. Biotypes 1/1/1 and 5/1/1, most frequently isolated and constituting about 37% of the total isolates, would be considered K pneumoniae by standard biochemical typing procedures. Of 65 cattle and environmental strains studied serologically, 11 serotypes, 14 biotypes, and 29 bioserotypes were identified, indicating the diversity of Klebsiella strains present in the herd. When strains from mastitic milk (n = 19) and the environment (n = 22) were compared, no bioserotype distinction or grouping that related to isolation source was obvious. The predominant bioserotype from both sources was 5/1/1-K35 (21.0% and 22.7% of the strains from mastitic milk and the environment, respectively). The growth inhibition by bovine serum of strains isolated from mastitic milk, the environment, and udder skin was similar. However, strains isolated from the mouth and rectum of the cow were significantly (P less than 0.05) more inhibited by serum.