Mannitol Agar w/Prilion is recommended as a selective agar medium for isolation and differentiation of Salmonella from Proteus species. Salmonella species being lactose-negative, mannitol-positive appears blue in colour and Proteus species being lactose-negative, mannitol-negative appear yellow in colour. This medium has mannitol as fermentable carbon source and metachrome yellow, water blue as indicator dyes.