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Mannitol salt agar or MSA is a commonly used selective and differential growth medium in microbiology. It encourages the growth of a group of certain bacteria while inhibiting the growth of others. This medium is important in medical laboratories by distinguishing pathogenic microbes in a short period of time.〔 〕 It contains a high concentration (~7.5%-10%) of salt (NaCl), making it selective for gram positive bacterium ''Staphylococci'' (and ''Micrococcaceae'') since this level of NaCl is inhibitory to most other bacteria.〔 (【引用サイトリンク】title=Mannitol salt agar )〕 It is also a differential medium for mannitol-fermenting staphylococci, containing carbohydrate mannitol and the indicator phenol red, a pH indicator for detecting acid produced by mannitol-fermenting ''Staphylococci''. ''Staphylococcus'''' aureus'' produce yellow colonies with yellow zones, whereas other ''Staphylococci'' produce small pink or red colonies with no colour change to the medium.〔 (【引用サイトリンク】title=Mannitol salt agar (7143) )〕 If an organism can ferment mannitol, an acidic byproduct is formed that will cause the phenol red in the agar to turn yellow.〔 It is used for the selective isolation of presumptive pathogen (pp) ''Staphylococci''. ==Expected results== * Gram + ''staphylococcus'' : fermenting mannitol: Media turns yellow (eg. S. aureus) * Gram + ''staphylococci'' : not fermenting mannitol. Media does not change color (eg. S. epidermidis) * Gram + ''streptococci'' : inhibited growth * Gram - : inhibited growth 〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mannitol salt agar」の詳細全文を読む スポンサード リンク
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