Which test is used to differentiate viridans streptococci from group D streptococci and enterococci?

The bile esculin test is used to differentiate viridans streptococci from group D streptococci and enterococci by assessing the organism's ability to hydrolyze esculin in the presence of bile salts. Group D streptococci, which includes enterococci, can grow in the presence of bile and hydrolyze esculin, leading to a positive reaction characterized by darkening of the medium due to the formation of esculetin and its reaction with iron salts. Conversely, viridans streptococci typically do not grow well in the presence of bile and therefore do not hydrolyze esculin, resulting in a negative test.

This distinction is critical in the clinical context, as it helps in correctly identifying the presence of pathogens that may be of clinical significance. In contrast, the other tests listed serve different purposes: the bacitracin disk test is primarily used to identify Streptococcus pyogenes, the CAMP test is utilized for the identification of Streptococcus agalactiae, and the hippurate hydrolysis test differentiates between certain species of streptococci based on their ability to hydrolyze hippurate. Therefore, the bile esculin test is the appropriate