Mac Conkey agar trypton 296 Nac 0. 5% lactose 1% bile salt 0. 5% phenol red pH 6.8-8.0,) agar1.5-2% Bile salt: inhibit the growth of gram positive bacteria phenol red: indicate the ph of the medium Selective differential mediumMacConkey agar trypton 2％ NaCl 0.5% lactose 1％ bile salt 0.5% phenol red ( pH 6.8～8.0,) agar 1.5-2% Bile salt inhibit the growth of gram positive bacteria phenol red indicate the pH of the medium Selective & differential medium ： ：