The Activity of Streptomycin in the Presence of Serum and Whole Blood. ∗

Summary

1. The activity of treptornycin on a susceptible strain of Staphylococczrs aureus was not changed in the presence of serum or whole blood. 2. The addition of fresh whole blood with or without immune serum did not augment streptomycin activity. 3. A resistant strain of Staph?dococcus aurcus was inhibited during the first 24 hours by streptomycin in low concentrations. This effect was augmented when serum was added to the medium. 4. Direct growth curves indicate that this inhibition by streptomycin ofa resistant strain was attributable to interference with growth of the organism rather than inactivation of labile constituents. 5. Phagocytosis in the presence of high concentrdtions of treptonlycin appears to be impaired. o. The bacteriostatic activity of streptomycin mas manifest on both susceptible and resistant strains. With the latter, thisinhibition was transitory. The bacteriostatic mechanisim and bactericidal mechanism aredissociated phenomena.