Differential media MacConkey Agar (MCA) .Ingredients peptone, lactose, bile salts, sodium chloride and pH indicator (neutral red) aBacteria that ferment lactose in the medlium w produce acid byproducts which will change the color of the ph indicator from yellow to redMacConkey Agar (MCA) Ingredients : peptone, lactose, bile salts, sodium chloride and pH indicator (neutral red). Bacteria that ferment lactose in the medium will produce acid byproducts, which will change the color of the pH indicator from yellow to red. Differential media