MSA (Mannitol Salts Agar)
Isolation and differentiation of pathogenic staphylococci, principally S. Aureus. Normally used in clinical environment. Selective - Sodium chloride; most other bacteria can't survive at this level of salinity. 7.5% sodium concentration. Staphylococci. Differential - Staph. aureus - sugar mannitol, pH indicator, phenyl red, pathogenic staph that can ferment mannitol will cause phenyl red to turn yellow. Staph can ferment mannitol. Most non-pathogenic staph cannot.