Bactericidal Activity of Bovine Serums Against Coliform Organisms Isolated from Milk of Mastitic Udders, Udder Skin, and Environment

Abstract

SUMMARY: Six strains of Klebsiella sp. isolated from mouth, udder skin, and milk of mastitic udders of cows, 6 coliform organisms from milk of acutely mastitic udders, 10 coliform organisms from the barn floor, and 1 stock strain of Aerobacter aerogenes (2414-2) were tested by spectrophotometric bactericidal assay against dilutions of serums (with and without added complement) of cows of known infection history. All degrees of susceptibility of the organisms to the bactericidal effects of serum were seen: The stock strain of A. aerogenes was highly susceptible; 2 strains of Klebsiella and 2 strains of coliforms from the barn floor were moderately susceptible; and the remaining strains were highly resistant. Addition of complement to the serums did not potentiate the reaction, but usually stimulated growth of the inoculums or might have inhibited the bactericidal action. Heating the serums at 56 C. for 30 minutes destroyed most of the bactericidal activity. Serums were variable in their potency against susceptible organisms, and the bactericidal activity was not significantly greater in the older cows which had had coliform mastitis.