Abstract
Summary and Conclusions
1. Certain organisms of the Smith strain Staphylococcus aureus possess a natural increased resistance to streptomycin. This resistance is not based on the production of a “streptomycinase.”
2. A strain of staphylococcus, highly resistant to streptomycin, can be produced in vitro from the streptomycin-sensitive organisms.
3. Streptomycin resistance is a relatively permanent characteristic, and is not affected by several passages through mice. The resistant organisms retain their virulence for this host. 4. Streptomycin resistance and penicillin resistance are independent of each other. Staphylococci originally penicillin-sensitive, retain their sensitivity to penicillin after being made resistant to streptomycin, and vice versa. Treatment with relatively large amounts of streptomycin is ineffective in mice infected with a streptomycin-resistant strain of Staphylococcus aureus. These mice can be cured, however, with penicillin. 5. The bacteriostatic effect of streptomycin diminishes considerably as the acidity of the culture medium increases from pH 7.7 to 5.2; the greatest diminution in effect occurs between pH 6.6 and 5.9. This must be taken into consideration in making in vitro assays and sensitivity tests, as well as in evaluating the action of the drug in vivo. 6. Streptomycin is not destroyed after contact with broth of pH 3.5 for 2½ hours. 7. Streptomycin is not destroyed, nor are its bacteriostatic and bactericidal powers appreciably influenced, by serous body fluids, pus, or normal tissue juices.
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