Bile Aesculin Medium is generally used for the differentiation and presumptive identification of Group D streptococci (enterococci). Enterococci hydrolyse aesculin forming, amongst other products, aesculetin which in turn combines with Ferric ammonium citrate producing a dark brown or black complex. The presence of Bile salts in the medium inhibits gram positive organisms other than enterococci. The medium can also be used for the presumptive identification of certain organisms within the Enterobacteriaceae group such as Klebsiella spp., Enterobacter spp., etc.