Trimethoprim-Sulphamethoxazole: Comparative Study in Urinary Infection in Hospital

Abstract

Trimethoprim is inhibitory for a wide range of bacteria, and when used in combination with a sulphonamide marked synergy has been reported. In order to test its value in the treatment of urinary infections 154 hospital patients with infections of varying severity and due to a wide range of organisms were treated with combinations of sulphamethoxazole and trimethoprim. Combinations of these substances in two different ratios (2:1 and 10:1) were used in 113 patients, and one week after the end of treatment about three-quarters were cured by both combinations. In a second study 106 patients were treated with a sulphamethoxazole-trimethoprim combination (5:1), ampicillin, or sulphadimidine. The cure rate with the 5:1 combination was higher than that found with ampicillin or sulphadimidine both one week after finishing treatment (sulphamethoxazole-trimethoprim 85%, ampicillin 70%, sulphadimidine 40%) and at the fourth- to fifth-week follow-up (sulphamethoxazole-trimethoprim 67%, ampicillin 52%, sulphadimidine 15%). The results obtained with the various sulphamethoxazole–trimethoprim combinations did not indicate that a particular ratio was superior for treating urinary infections in general or for those caused by any particular species of organism. Laboratory studies showed that many bacteria causing urinary infections in hospital were sensitive to trimethoprim, and the therapeutic results could have been largely predicted from a knowledge of the in-vitro sensitivity tests to trimethoprim alone. For example, sulphamethoxazole–trimethoprim in the treatment of Proteus mirabilis infections was less successful than in those due to Escherichia coli, and this finding was clearly reflected in the higher minimal inhibitory concentrations for trimethoprim of Pr. mirabilis. The sulphamethoxazole–trimethoprim combination was simple to administer, free from side-effects, and gave satisfactory results in the treatment of urinary infections that occurred in hospital patients.