Phenol Red Mannitol Agar

Phenol Red Mannitol Agar is recommended for studying mannitol fermentation by the pure cultures of microorganisms. Positive reaction is indicated by the production of a yellow colour in agar due to acid production. Gas production is indicated by the splitting of agar or by the bubbles formation. Escherichia coli, Klebsiella pneumoniae and Salmonella Typhimurium are known mannitol fermentors and gives positive reaction. Shigella flexneri ferments mannitol but does not produce gas. Alcaligenes faecalis and Proteus vulgaris do not ferment mannitol, hence there is no colour change of the medium.