Mannitol salt agar contains (among other ingredients) extracts of animal tissue and mixed proteins, along with sodium chloride, which inhibits the growth of organisms other than those in the genus staphylococcus. it also includes mannitol, which is fermented by staphylococcus aureus, turning the medium yellow. other species of staphylococcus (which do not ferment mannitol) will still grow, but the medium remains red in color. mannitol salt agar could be classified as

selective and differential medium

Explanation:

Based on chemical composition, there are different type of media for the cultivation of bacteria:

Basal media: culture media that needs no enrichment before being used for bacteria cultivation.Enriched media: culture media that are enriched with the addition of blood, serum or egg before being used for culturing.Selective media: These are media that selectively favour the growth of a bacterium or group of bacteria over others.Differential media: Also known as indicator media. They contain a special substance that changes colour to indicate the presence of a bacterium or group of bacteria.Transport media: Media that are used in transporting bacteria from point of collection to where they will be cultured.Storage media: These are media that are used to store organisms for future use.

Mannitol salt agar selectively favours the growth of the genus Staphylococcus and inhibits the growth of other organisms. It also contains mannitol which gets fermented and change colour to indicate a particular species of the genus. Hence, mannitol salt agar could be classified as a selective and differential medium