Experimental Infection and Streptomycin Treatment in Irradiated Mice

Abstract

Of 8 organisms tested, all but 2 strains of a-streptococcus resulted in increased mortality in mice irradiated with 475 r. Streptomycin was effective with Staphylococcus aureus, partially effective with paracolon, Escherichia coli and Proteus, and ineffective with Pseudomonas infections. With Proteus Kf 7, streptomycin reduced mortality only during the first 2 days after infection, although in both early and late periods there was a reduction in the incidence of positive blood cultures. Treatment for 3 days with 1.25 mg. 1 day of streptomycin was almost as effective in reducing mortality, though not as effective in reducing the incidence of positive blood cultures, as longer treatment with 2.5 or 5 mg. twice a day. Susceptibility to Proteus showed no further increase, nor did the efficacy of streptomycin show a decrease, from the 3d through the 12th day after irradiation with 475 r. After a radiation dose as low as 250 r the animal still showed marked susceptibility to Proteus infection. Streptomycin was more effective at 250 r than at 475 r.