A clinical isolate is presumptively identified as S. aureus by means of several simple procedures:
Gram stain: Gram-positive cocci, occurring singly, in pairs, or "bunches of grapes."
Catalase test: Staphylococci are catalase-positive, distinguishing them from streptococci which are catalase-negative.
Coagulase test: S. aureus is coagulase-positive.
DNAse test: S. aureus is DNAse-positive.
Heat stable endonuclease: S. aureus is positive.
There are also many commercial kits available for identification of S. aureus based on latex agglutination.
