Effect of Sulfonamides on Action of Penicillin

Abstract

The in vitro effects of combined penicillin and sulfadiazine under various conditions are described in detail. The observed effects are dependent on 1) the conc, of each agent, 2) the number of organisms present, 3) the environmental conditions, 4) the degree of susceptibility to each agent, and 5) the species of organisms involved. With small numbers of sulfadiazine-sensitive organisms and less than a bacteriostatic conc, of penicillin, sulfadiazine increases bacteriostasis. With bacteriostatic cones, of penicillin, sulfadiazine appears to increase bacteriostasis, provided the number of organisms present at the end of the sulfadiazine lag period is low. Under conditions in which sulfadiazine decreases the rate of multiplication, the rate at which penicillin acts is likewise decreased.