Moderately selective differential medium for the isolation and differentiation of Enterobacteriaceae.

The Fuchsin contained in the Lactose-Fuchsin-Sulphite agar is liberated by the reaction with acids and acethaldehydes, both are metabolites of lactose-fermenting bacteria. The liberated Fuchsin results in a red colour with a greenish metallic sheen of the colonies of coliform microorganisms, whereas the Endo agar is dyed similarily. In contrast, lactose-negative microorganisms appear in colourless colonies before the light pink background of the nutrient medium. Simultaneously, the fuchsin sulfite partially inhibits the growth of gram-positive bacteria.