Antimicrobial susceptibilities of nutritionally variant streptococci.

Seventeen strains of nutritionally variant streptococci were examined for susceptibility to 15 antimicrobial agents. All strains grew in blood culture medium containing blood and blood products or, in the absence of blood or blood products, in broth containing glucose and pyridoxal hydrochloride. Growth was enhanced by incubation in an atmosphere containing 5%-10% CO2 or, in some cases, was CO2-dependent. Rifampin, penicillin, clindamycin, and erythromycin were the most active antibiotics tested with minimal bactericidal concentrations of 2, 1, 2, and 2 microgram/ml, respectively, for 90% of the strains; the corresponding values for vancomycin and streptomycin were 32 and 16 microgram/ml, respectively.