Observations on the Mode of Action of Sulfanilamide in vitro

Abstract

Summary

1. Repeated transfer of a virulent strain of hemolytic streptococcus in 1-10,000 sulfanilamide-broth does not attenuate the organism under certain experimental conditions. 2. The combined bactericidal action of antibody and sulfanilamide is greater than that of either one alone. 3. In dilute solutions sulfanilamide promotes phagocytosis, probably nonspecifically. 4. In 25% horse-serum neopeptone-water containing sulfanilamide, hemolytic streptococci form long chains and very large capsules. 5. Organisms previously grown in sulfanilamide are rapidly inhibited in fresh media containing sulfanilamide, whereas normal organisms multiply at the usual rate for several hours in the presence of sulfanilamide before bacteriostasis occurs. Evidence is presented to show that this delay is due to the formation of a loose union between the drug and the organisms rather than to any change brought about in the medium. 6. The bacteriostatic effectiveness of sulfanilamide varies directly with the concentration of the drug and inversely with the size of the inoculum. 7. The addition of specific antibody does not significantly enhance the bacteriostatic effect of the drug in fresh human serum, although it markedly increases the bactericidal effect of sulfanilamide in whole blood. 8. It is suggested that the effectiveness of a given concentration of sulfanilamide depends largely on the number of organisms present at the time when bacteriostasis begins, and this is dependent on the number of organisms inoculated and their rate of multiplication.