COMPARISON OF TESTS DESIGNED TO IDENTIFY STAPHYLOCOCCUS-AUREUS THERMOSTABLE NUCLEASE

The thermonuclease test has been employed for same-day identification of Staphylococcus aureus in blood cultures and a seroinhibition test t o confirm S. aureus thermonuclease (TNase) by using polyclonal anti-S. aureus TNase antiserum. However, strains of non-S. aureus staphylococ ci may produce TNases which are neutralized by the antiserum. This stu dy evaluated alternative reagents and confirmatory tests for the S. au reus ens TNase. The tests included seroinhibition by a monoclonal anti body (MAb) against S. aureus TNase, MAb-based detection of the TNase i n a sandwich ELISA, and a polymerase chain reaction for amplification of the nuc gene encoding the S. aureus TNase. All these tests discrimi nated between TNase produced by S. aureus and TNase produced by strain s of the species S. caprae, S. carnosus, S. simulans, S. capitis, and S. intermedius. Specificity for the S. aureus TNase was confirmed by a n inhibition ELISA for two out of three MAbs tested. Thus, the MAb and nuc-based tests will be useful to discriminate between TNases from S. aureus and non-S. aureus staphylococci.