The use of sodium azide in selective media for streptococci

Abstract

In order to isolate streptococci from the nasal cavities of horses, the authors used glucose-sodium azide-violet crystal-broth medium, and wcre thus able to eliminate almost ali contaminating flora. Out of 89 strains of contaminating material inoculated both in glucose broth and gl.sod.az.viol.crys.broth, 31.5% of positive results were obtained in the former medium, while in the latter, results were positive in 91%. The colonies were counted after 3, 5 and 8 hours of incubation in both media mentioned, evidence being thus obtained that the g.s.a.v.c.broth, although highly selective docs not stimulate the multiplication of streptococci. The advantage of growing contaminated material in the suggested medium for the purpose of streptococcus isolation, specially if the material requires previous homogenization, is emphasized.