Bacterial Deoxyribonuclease Production and Its Possible Influence on Mastitis Detection

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Abstract
Various hemolytic streptococci, hemo- lytic staphylococci, and micrococci were tested for production of deoxyribonuclease (DNase). In general, beta-hemolytic path- ogenic streptococci of human origin pro- duced highest concentrations of DNase. However, some beta-hemolytic bovine strains were also highly productive. Alpha- hemolytic strains produced a maximum of 7.6 units/milliliter. None of the staphy- lococci or micrococci produced detectable DNase. The possibility of correlating DNase production with pathogenicity of the organism is suggested. Addition of DNase to milk abolished the California Mastitis Test (CMT) reaction only after leucocytes had been disrupted by the surface active agent. Possible effects of bacterial DNase pro- duction in milk on mastitis screening tests such as the CMT are discussed. Microorganisms. Twenty-nine strains of bo- vine mastitis streptococci, nine strains of strep- tococci of human origin, nine strains of bovine mastitis staphylococci, and two strains of micro- cocci were tested for production of DNase. The strains of bovine origin were representative of isolates from herds throughout the state. The staphylococci and micrococci were chosen to represent distinctly different strains based on biochemical tests and phage-type data. The strains isolated from humans were obtained from the University Medical Microbiology De- partment. The organisms were grown in brain heart infusion broth (B.B.L.) for 24 hr at 37 C. Sterile culture filtrates were obtained by filtra-