Free coagulase and thermostable nuclease reactions of staphylococci: a comparison

Two-hundred-fifty-five staphylococcal isolates (clinical) were tested for both free coagulase (CGase) and thermostable nuclease (TNase) production. Two-hundred-ten of the 255 isolates were identified as Staphylococcus aureus when both strongly positive TNase and CGase reactions (human and rabbit plasma) were observed with these strains. Forty-five of the 255 isolates were identified as Staphylococcus species, other than S. aureus when either weakly positive TNase and CGase (rabbit plasma) reactions or negative TNase and CGase (rabbit and human plasma) reactions were observed. This experiment suggest that the identification of staphylococcal isolates as S. aureus can be based upon demonstration of both strongly positive TNase and CGase reactions.