Comparison of Antibacterial Activity of Single and Combined Sulfonamides.

Conclusions 1. The antibactericidal activity of various mixtures of sulfonamides is unpredictable. 2. The observed effect varies markedly with different species and with various strains of the same species of organism. 3. Depression of bactericidal potency against both gram negative and positive bacteria frequently results from combining sulfonamides. 4. The greatest and most constant decrease in antibacterial effect is produced by mixing sulfamerazine, sulfathiazole, and sulfadiazine. 5. These results suggest that combinations of sulfonamides may have little clinical usefulness in many instances, since they are often not as effective as the single agents which compose them.