Detection of Staphylococcus aureus in blood cultures: evaluation of a two-hour method

Aurease--one of three tests on the RAPIDEC staph system for two-hour identification of the main clinically important staphylococci--was used for the direct detection of Staphylococcus aureus from 102 blood culture broths in which Gram-positive cocci were seen. A pellet of centrifuged blood culture broth was used as the inoculum. The method was compared with the thermonuclease test and subsequent isolates subjected to probabilistic identification based on biochemical reactions. A positive aurease test and the presence of thermonuclease were detected in 27 samples, subsequent identification showing all to be Staph. aureus. A further Staph. aureus strain was aurease negative but thermonuclease positive. None of the remaining 74 specimens was positive by the aurease test, which is rapid, sensitive and specific for detection of Staph. aureus in blood culture broths.