N-formimidoyl-thienamycin and norfloxacin against multiple-resistant Pseudomonas aeruginosa strains. Combined in vitro activity and comparison with 14 other antibiotics.
The in vitro susceptibility of 54 multiple-resistant strains of Pseudomonas aeruginosa to 16 antipseudomonal agents were determined. The majority of these organisms were also beta-lactamase-producing strains. Norfloxacin, N-formimidoyl-thienamycin and aztreonam showed the best antipseudomonal activity, with minimum inhibitory concentrations for 90% of isolates (MIC90) of 2, 8, and 8 mg/l respectively. Of the aminoglycosides, only amikacin (MIC90 = 32 mg/l) showed satisfactory activity, whereas among beta-lactam antibiotics, cefotaxime, ceftriaxone and moxalactam (MIC90 = 32 mg/l) were more active than cefoperazone (MIC90 = 128 mg/l), cefsulodin (MIC90 = 128 mg/l), piperacillin (MIC90 = 512 mg/l) and azlocillin (MIC90 = 1024 mg/l). A synergistic or partially synergistic interaction (fractional inhibitory concentration index less than 1) was demonstrated in vitro against 37% of the strains when N-formimidoyl-thienamycin was combined with norfloxacin.
D000583:Amikacin / Q000494:pharmacology; D000617:Aminoglycosides / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001398:Aztreonam / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D015378:Imipenem; D008826:Microbial Sensitivity Tests; D009643:Norfloxacin / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D013845:Thienamycins / Q000494:pharmacology*
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D013845:Thienamycins; D015378:Imipenem; D000583:Amikacin; D001398:Aztreonam; D009643:Norfloxacin