Effect of Group A Streptococci on Transplantable Leukemia of Mice

Two hundred AKR mice with submaxillary tumors produced by the intranasal deposition of ascites-form leukemic cells were superinfected with Group A streptococci at 48- and 72-hour intervals. Of 100 mice which received streptococci 48 hours after instillation of leukemic cells, 54 developed superimposed infection of the tumor-bearing nodes. After treatment with penicillin, 48 mice survived and remained tumor-free. Of the 100 mice which received streptococci 72 hours following tumor transplants, 32 developed superimposed infection of the tumor-bearing nodes. After treatment with penicillin, 26 mice survived and remained tumor-free. Infected tumor-bearing mice survived longer than did uninfected tumor-bearing controls. Mean survival times in days were: tumor control series, 14.5 ± 0.6; 48-hour infected series, 22.6 ± 0.1; and 72-hour infected series, 18.2. Infected tumor-bearing animals in both the 48- and 72-hour series showed a significant absolute increase in survival over the uninfected ascites control mice.