DEOXYRIBONUCLEASE ACTIVITY OF MICROCOCCI FROM CLINICAL SOURCES

Abstract

Cultures of Staphylococcus aureus yield a deoxyribonuclease (DNase) that differs from other described DNases in several properties, including pH optimum (8.6), cation activator (calcium), and heat stability. The effects of certain culture conditions of DNase activity were studied. High DNase activity was found in brain heart infusion cultures incubated with continuous shaking at room temperature for 40-72 hours. These conditions were employed in investigating DNase activity of 87 strains of staphylococci recently isolated from clinical material. Each strain was examined also for coagulase reaction, nitrate reduction, utilization of ammonium phosphate as sole source of nitrogen, gelatin liquefaction, mannitol fermentation, and colonial pigmentation. The 34 coagulase positive strains of the group all exhibited high DNase activity. Significantly low DNase activities were produced by all coagulase negative strains except one; this strain exhibited the characteristics of S. aureus except for the coagulase reaction. Thus, high DNase activity may be a useful determinative characteristic, supplementing coagulase and phosphatase reactions, in identifying potentially pathogenic staphylococci. In addition, the possibility is discussed that the kind of DNase produced by cells may be a taxonomic characteristic useful in studies of natural relations among bacteria.