[Synergism of colistin and sulfonamide in proteus species (author's transl)].

In agar diffusion testing of Proteus mirabilis strains sensitive to sulfonamide a synergistic effect of colistine (C) and sulfonamide (S) was demonstrated. By quantitative evaluation these results were confirmed in 100 strains of Proteus mirabilis and 100 strains of indol-positive Proteus spp. using broth dilution method. Combining 1 part C with 10 parts S the mean increase in sulfonamide sensitivity was enhanced fourfold. Increasing the inoculum sensitivity of Proteus against the combination of C and S was still found to range within therapeutic blood levels. Therefore in treatment of Proteus infection the positive synergistic effect of C+S should be taken into consideration.