Which of the following enzymatic tests is used to identify enterococci?

The bile esculin test is used to identify enterococci due to its ability to hydrolyze esculin in the presence of bile salts. Enterococci, particularly Enterococcus faecalis, can grow in a high-bile environment and convert esculin into esculetin, which then reacts with iron salts in the medium to form a dark brown precipitate. This property is a distinguishing characteristic of enterococci and helps differentiate them from other gram-positive cocci.

The other tests listed serve different purposes and are specific to other bacteria: the optochin disk test is used to differentiate Streptococcus pneumoniae from other alpha-hemolytic streptococci; the CAMP test is used to identify Streptococcus agalactiae; and the bacitracin disk test is utilized to assess sensitivity to bacitracin, primarily for the identification of Streptococcus pyogenes. Therefore, the bile esculin test is the most appropriate choice for identifying enterococci.