Abstract
Group A streptococcus mutants, which lost the ability to produce soluble hemolysins, either β or α hemolytic on the horse blood agar, showed penicillin-mitomycin C double resistance. Penicillin resistance was high and stable, but mitomycin C resistance was not remarkably high. Mitomycin C resistance was always accompanied with inactivation of the antibacterial activity of the drug, while mitomyciri C and penicillin sensitive group A streptococci never showed mitomycin inactivation. The component affecting the mitomycin C was not found in the sterile filtrate of mutant cell cultures, nor could it be extracted by sonic oscillation. The activity of the factor diminished, when living mutant cells were heated at 60C for 30min, but activity was not diminished at 56C. The intensity of activity was α function of the bacterial quantities used. Mutant cells suspended in heart infusion broth, proteose peptone, casamino acid and horse serum were able to render the factor which inactivated mitomycin C, while mutant cells suspended in bovine serum albumin, RNA, or saline did not show the phenomenon.
