Observations on the Mode of Action of Sulfapyridine on Pneumococcus. ∗

Abstract

Conclusions

1. Sulfapyridine did not affect the capsule of the pneumococcus either in vivo or in vitro in such a way as to be ascertainable by capsule-staining or by affecting the “quellung” reaction in the presence of immune serum. 2. In vivo and in vitro experiments using sulfapyridine in pneumococcal infections or pneumococcal cultures containing leucocytes did not indicate an increase in phagocytosis of the diplococci in the presence of the drug. 3. In vitro there was only slight bacteriostatic effect of 10 mg% sulfa-pyridine in broth cultures of pneumococcus Type I until the culture neared the close of the logarithmic phase of growth. At that time a bactericidal effect was apparent along with increased bacteriostasis and the length of the phase of decline was decreased markedly. 4. In vivo a similar effect was noted. In mice treated with sulfa-pyridine there was a short period of increase in the number of organisms in the peritoneal exudate followed by a rapid decrease in the number of bacteria found until, after 18 hours, only a few organisms remained. In several days, after stopping administration of the drug, the treated mice died and pneumococci were recovered from the heart-blood and peritoneal exudate.

5. Complete bactericidal action was not demonstrated.

6. It would seem that sulfapyridine may owe its beneficial effect in pneumococcal infections to its bacteriostatic action which may permit antibodies to be formed by the body or to be acquired passively, or allow the inhibited organisms to be disposed of by phagocytosis at the normal rate.