Same-day confirmation of Staphylococcus aureus bacteraemia by a thermonuclease test

A test to detect thermostable DNase activity (TDNase test) was evaluated for rapid confirmation of S. aureus bacteraemia, using toluidine blue O DNA agar plates for the testing. A total of 226 blood cultures which grew bacteria were examined. S. aureus was identified in 76 of the cultures. All of the S. aureus isolates showed positive TDNase test after 2 h of incubation of the test plates. The remaining isolates examined, most of them coagulase-negative staphylococci, showed a negative test. The TDNase test enables reliable same-day confirmation of S. aureus bacteraemia.