[Tolerance of group A streptococci to the bactericidal effect of various antibiotics].

The MICs and MBCs (minimum bactericidal concentration) of 6 antibiotics (benzylpenicillin, oxacillin, cephalothin, ristomycin, erythromycin and lincomycin) for 50 strains of group A streptococci were determined with serial dilutions in a liquid medium (the medium for isolation of streptococci of the I. I. Mechnikov Moscow Research Institute of Vaccines and Sera) followed by volumetric platings on a solid medium (the same medium supplemented with 1.5 per cent agar). The results are discussed in relation to the problem of Streptococci tolerance to the bactericidal effect of the antibiotics.