Sensitivity of differentPseudomonas species andAeromonas hydrophila to trimethoprim and sulfamethoxazole separately and in combination

An agar dilution method was used to determine thein vitro sensitivity of differentPseudomonas species andAeromonas hydrophila to trimethoprim, sulfamethoxazole, and a combination of these drugs maintaining a ratio of one to twenty. The fluorescent pseudomonads (Pseudomonas aeruginosa, P. putida, andP. fluorescens) were generally resistant to the drugs separately and combined. For otherPseudomonas species the sensitivity of the isolated strains to the drugs were variable and a synergistic effect of the combination was found for about half of the strains.Aeromonas hydrophila was generally sensitive to both drugs and a stronger synergistic effect of the combination was found than for the pseudomonads.