Combinations of antimicrobial agents: II. The in vitro sensitivity of 52 strains of proteus species to sulphafurazole, polymyxins and combinations of sulphafurazole and polymyxins.

The sensitivity of 52 strains of Proteus species to sulphafurazole, polymyxins and the combinations of sulphafurazole and polymyxins was determined by means of discs and trays. It was found that 2 and 6 strains, respectively, were sensitive to discs containing 100 mug sulphafurazole and 300 mug polymyxin B, respectively, 41 strains were sensitive to the combination of discs containing 100 mug sulphafurazole and 50 mug colistin, respectively, and 38 strains were sensitive to the combination of discs containing 100 mug sulphafurazole and 300 mug polymyxin B, respectively. The tray method proved that 2 and 5 strains were sensitive to 25 and 200 mug sulphafurazole, respectively, and that 1, 2 and 3 strains were sensitive to 25, 50 and 100 mug polymyxin B, respectively. Also 41 strains were sensitive to the combination of 100 mug sulphafurazole and 25 mug colistin and 38 strains were sensitive to the combination of 25 mug sulphafurazole and 6.3 mug polymyxin B. There was good agreement between the results of the disc and of the tray studies. The synergism between sulphonamides and polymyxins may offer therapeutic possibilities.