Bile Esculin Agar is used for isolating and presumptively identifying Group D Streptococci based on their ability to hydrolyze Esculin. This glucoside is hydrolyzed to esculetin and dextrose by the bacteria. The former reacts with Ferric Ammonium Citrate to form a dark brown or black complex. Oxbile inhibits Gram-positive bacteria not belonging to the Enterococci group. Beef Extract and Enzymatic Digest of Gelatin provide essential nitrogenous sources and carbohydrates for bacterial growth. Agar is the gelifying agent.