COMPARATIVE ANTIMICROBIAL ACTIVITY OF FK037, CEFPIROME, CEFTAZIDIME AND CEFEPIME AGAINST AMINOGLYCOSIDE-SENSITIVE AND AMINOGLYCOSIDE-RESISTANT PSEUDOMONAS-AERUGINOSA AND PSEUDOMONAS SPP

The activities of FK037, cefpirome, ceftazidime and cefepime against 7 1 aminoglycoside-resistant, 35 aminoglycoside-sensitive, 29 cystic fib rosis Pseudomonas aeruginosa isolates, and 31 Pseudomonas spp. strains were studied using the agar dilution technique (final inoculum 10(4) c.f.u./spot). The MIC(90) for aminoglycoside-sensitive P. aeruginosa. against FK037, cefpirome, ceftazidime and cefepime was 32, 16, 8 and 1 6 mg/l, respectively. The MIC(90) for P. aeruginosa strains resistant to one or more aminoglycosides was similar for FK037, cefpirome and ce ftazidime (128 mg/l) and two dilutions lower for cefepime (32 mg/l). T he MIC(90) for P. aeruginosa isolates highly resistant to all three am inoglycosides (MIC greater than or equal to 128 mg/l) was 64 mg/l for FK037 and cefpirome, and 32 mg/l for ceftazidime and cefepime. The MIC (90) for P. aeruginosa from patients with cystic fibrosis was 32 mg/l for all four cephalosporins tested, and 8, 32 and 64 for tobramycin, g entamicin and amikacin, respectively. Xanthomonas maltophilia was resi stant to all four cephalosporins and three aminoglycosides. The activi ty of ceftazidime and cefepime was one to two dilutions greater agains t P. cepacia and If picketti than of FK037 and cefpirome. The activity of ceftazidime was two dilutions greater than the other three cephalo sporins against P. fluorescens. In kinetic time kill curves against If aeruginosa, all four cephalosporins demonstrated similar activity at 6 and 24 h when tested at 1 x MIC. At 2 x MIC, regrowth was less at 24 h for cefepime, cefpirome and FK037 than for ceftazidime. In time kil l curves for P. aeruginosa, synergy was dearly demonstrated at 1/4 MIC and 1/2 MIC concentrations for FK037 and tobramycin.