Mannitol Salt Agar (MSA)
a) The yellow indicates the organism can ferment mannitol and will produce acid fermentation products which lower the pH, causing the phenol red indicator to turn yellow.
b) The yellow indicates the organism cannot ferment mannitol and will not produce acid fermentation products.
c) The yellow indicates the organism can ferment mannitol but will not produce acid fermentation products.
d) The yellow indicates the organism cannot ferment mannitol but will produce acid fermentation products.