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, distinguishes 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.