The Effect of Para-Aminobenzoic Acid on the Chemotherapeutic Activity of the Sulfonamides in Lymphogranuloma Venereum and in Duck Malaria.

It is now well established that para-aminobenzoic acid inhibits the action of sulfonamides on bacteria in vitro and in vivo .(Rubbo and Gillespie, 1940; Selbie, 1940; Woods, 1940). Wiedling (1941) found that para-aminobenzoic acid produced an inhibition of the effect of sulfanilamide, sulfapyridine and sulfathiazole on the fresh water diatom Nitzschia palea var. debilis. Experiments published by Dimond (1941) showed that para-aminobenzoic acid interfered with the action of sulfanilamide on the fungus Trichophyton purpureum. Findlay (1940) has reported that para-aminobenzoic acid inhibited the action of sulfanilamide on a strain of lymphogranuloma venereum. In this communication experiments will be reported which demonstrate the inhibiting effect of para-aminobenzoic acid on the chemotherapeutic activity of sulfamethyldiazine in Plasmnodium lophurae infections in Pekin ducklings. Experiments will also be presented in which, contrary to the experience of Findlay (1940), we were unable to show that para-aminobenzoic acid neutralized the action of sulfanilamide and sulfamethyldiazine on a strain of lymphogranuloma venereum.