Which biochemical test is used to identify Group A, beta-hemolytic streptococci?

The biochemical test used to identify Group A, beta-hemolytic streptococci is bacitracin susceptibility. In this test, a small disk containing bacitracin is placed on an agar plate that has been inoculated with the suspected streptococcal organism. If the organism is Group A streptococcus (Streptococcus pyogenes), it will show a zone of inhibition around the bacitracin disk, indicating sensitivity and confirming its identity.

This method is specific to Group A streptococci and is a reliable and straightforward way of differentiating them from other hemolytic streptococci, particularly Group B streptococci (Streptococcus agalactiae), which are resistant to bacitracin.

Other tests listed, such as optochin susceptibility, bile esculin positivity, and hippurate hydrolysis, are relevant for differentiating other types of streptococci. For example, optochin susceptibility is used to identify Streptococcus pneumoniae, bile esculin positivity is often associated with Enterococcus species or Group D streptococci, and hippurate hydrolysis is specific for differentiating Group B streptococci from Group A. Thus, they are