The use of bacitracin for identifying group A haemolytic streptococci.

The recognition of Lancefield's Group A as the most,commonly pathogenic members of the haemolytic streptococci has prompted several attempts at devising a rapid cultural diagnostic method such as the addition of maltose or glucose to blood agar, which alters the haemolytic activity of Group A strains (Kodama, 1937; Simmons and *Wilson, 1941). This paper describes the use of an antibiotic that is more inhibitory for Group A than for other haemolytic streptococci. The investigation was begun because it was noticed that the growth of haemolytic streptococci was inhibited by a contaminating colony of an organism subsequently identified as B. licheniformis. Further study showed that the inhibitory agent was almost certainly identical with the antibiotic bacitracin (Johnson, Anker, and Meleney, 1945) and an extended investigation was made of the use of bacitracin for the identification of Group A streptococci.