Bile Aesculin Agar

Bile Esculin Agar is used for the selective isolation and differentiation of group D streptococci from foods and is not intended for use in the diagnosis of disease or other conditions in humans.

Bile Esculin Agar is based on the formulation described by Swan and further evaluated by Facklam and Moody. Rochaix first noted the value of esculin hydrolysis in the identification of enterococcci. Meyer and Schonfeld added bile to the esculin medium and demonstrated 61 of 62 enterococci strains were able to grow and hydrolyze esculin, while other streptococci could not.

Molecular taxonomic studies of the genus Streptococcus have placed enterococci, previously described as group D streptococci, in the genus Enterococcus. The ability to hydrolyze esculin in the presence of bile is a characteristic of enterococci and group D streptococci. Swan compared the use of an esculin medium containing 40% bile salts with the Lancefield serological method of grouping, and reported that a positive reaction on the bile esculin medium correlated with a serological group D precipitin reaction. Facklam and Moody found that the bile esculin test provided a reliable means of identifying group D streptococci and differentiating them from non-group D streptococci.