Combinations of antimicrobial agents. III. The in vitro sensitivity of 12 strains of Pseudomonas aeruginosa and 12 strains of proteus species ot sulphamethoxazole + trimethoprim (co-trimoxazole), polymyxins and combinations of co-trimoxazole and polymyxins.

The sensitivity of 12 strains of Pseudomonas aeruginosa and of 12 strains of Proteus species to co-trimoxazole, polymyxins and combinations of co-trimoxazole and polymyxins was determined by disc and tray methods. It was found that all strains were sensitive to the combinations of co-trimoxazole and polymyxins. The disc study of the strains of Ps. aeruginosa revealed a typical image with many strains. The tray study gave a typical image with two strains of Proteus species. The two images are briefly discussed. The synergistic action of co-trimoxazole and polymyxins may well offer therapeutic possibilities.