Most of the group D streptococci have the ability to hydrolyze esculin to esculetin. Bile esculin agar base is composed of meat extract (Equivalent to beef extract), peptone, oxgall, ferric citrate and agar.
Meat extract and peptone provide nitrogen and other necessary minerals. Oxgall is a selective agent that inhibits gram-positive bacteria other than enterococci. Ferric citrate is an indicator of esculin hydrolysis.
The esculin (glycoside) is the source of carbon. The esculin hydrolyzing microorganisms hydrolyzes esculin to esculetin and dextrose. The esculetin reacts with ferric citrate to form a brown or black color complex. Agar is the solidifying agent.
Use: Recommended for isolating and presumptive identification of group D streptococci.
