Staphylococcus aureus identification: thermonuclease agar for direct testing of blood isolates and a new slide...

Simulated blood cultures were used to evaluate Thermonuclease agar (Remel) for distinguishing Staphylococcus aureus from coagulase-negative staphylococci (CNS) without subculture to agar media, and a new slide agglutination test (Staphylochrome; Innovative Diagnostic Systems) was evaluated for its ability to distinguish S. aureus from CNS after growth on blood agar. A total of 125 S. aureus and 124 CNS isolates were tested by each method. Reference identification methods included tube coagulase, thermonuclease detection from solid media, and biochemical characterization. Direct thermonuclease testing with simulated blood cultures correctly identified all 249 isolates. Staphylochrome correctly identified 121 of 125 S. aureus and all CNS isolates. S. aureus was reliably distinguished from CNS by both tests evaluated in this study.