Bromcresol green dextrose broth for the presumptive identification of group B streptococci

A 1 percent dextrose broth using bromcresol green as a pH indicator is described for the presumptive identification of group B streptococci. The results in the medium are read after 24 hr incubation at 36C as a color change. This medium was tested using 550 strains of streptococci belonging to groups A, B, C, D, and G. All of the group A strains were negative whereas all of the group B and Group D strains were positive. Thus, by using bacitracin susceptibility, esculin hydrolysis, and BCG dextrose broth, the presumptive identification of the frequently encountered streptococci can be accomplished.