Identification of Group A Streptococci

During the course of a project which had as its primary objective the evaluation of a streptococcal disease control program,¹an opportunity was presented to compare the efficacy of (a) the bacitracin disc method and (b) the fluorescent antibody method of identifying Group A streptococci with the Lancefield precipitin technique. The results which were obtained and are here presented are confirmatory of previous work²,³and show that both the bacitracin disc and the fluorescent antibody techniques are highly reliable. Each, therefore, represents a useful method for the identification of Group A streptococci in clinical laboratories. Methods A total of 776 strains of streptococci was subjected to study; 669 (90%) were isolated from patients who were seen on the clinical services of the Denver General Hospital, while 69 strains (10%) were obtained from household contacts of patients included in the study. Of the streptococcal isolations, 76% were made from