Mannitol-Egg-Yolk-Polymyxin Agar Base（Granular）

Testing principle:Peptone and Beef Extract serve as nutrients in the medium， providing carbon sources， nitrogen sources， vitamins， and mineral elements required for bacterial growth；Mannitol serves as a carbohydrate and a fermentable carbon source；Phenol Red serves as an acid-base indicator; Agar serves as the solidifying agent; 50% Egg Yolk provides lecithin; Polymyxin B inhibits the growth of other bacteria. Bacteria that ferment mannitol grow on this medium and produce acid， turning the colonies and the surrounding medium yellow. Bacteria that produce lecithinase hydrolyze lecithin， forming a white precipitate ring around the colonies. Bacillus cereus is mannitol-negative and lecithinase-positive; therefore， its colonies appear pink with a white precipitate ring surrounding them。