The Endo agar is used for isolation and differentiation of enterobacteria by the lactose fermentability. The mechanism of action of the environment is based on the ability of Magenta to form a colorless complex with sulfite. Bacteria that grow on the medium are divided into two groups. Those bacteria that do not ferment the lactose and grow as colorless colonies. Lactose-fermenting bacteria form aldehydes. In turn, aldehydes bind sulfite, and free Magenta giving the colonies a red color, sometimes with a metallic sheen.

Medium before using not sterilized. Sowing is carried out by the surface method, the cultivation is conducted at 37 ° C, the result is evaluated after 18-24 hours.