Synergism between sulphonamide drugs and antibiotics of the polymyxin group against Proteus sp. in vitro

Interesting synergism in vitro between a recently introduced antibiotic, colistin methane sulphonate, and sulphonamide drugs is described. The observations were extended to polymyxin B sulphate and sulphonamides with essentially similar results. The combinations are bactericidal at therapeutic levels, the ratio of drugs to one another is not critical, and the effect is present over a fairly wide pH range.