Antibacterial properties of investigational, new, and commonly used antibiotics against isolates of Pseudomonas cepacia in Michigan.

Microdilution antimicrobial susceptibility testing was performed with 73 isolates of Pseudomonas cepacia collected from the sputum of patients throughout Michigan with cystic fibrosis. Susceptibility testing was done using new and investigational antibiotics (loracarbef, cefixime, cefpirome, desacetyl-cefotaxime, cefpodoxime, cefmetazole, cefepime, cefprozil, and fleroxacin) and commonly used antibiotics (ceftazidime, mezlocillin, piperacillin, ciprofloxacin, tobramycin, and amikacin). Ceftazidime was the most active antibiotic, and 91.8% of isolates were susceptible to it with MIC50 and MIC90 values of < or = 4 and 16 micrograms/ml, respectively. For mezlocillin, piperacillin, and ciprofloxacin 84.9, 89 and 39.7% of the isolates, respectively, were mostly moderately susceptible. Loracarbef, cefixime, cefprozil, cefmetazole, cefepime, fleroxacin, cefpodoxime, tobramycin, and amikacin did not show activity against P. cepacia. For cefpirome and desacetylcefotaxime 24.7 and 60.3% of the isolates, respectively, were moderately susceptible. Both MIC50 and MIC90 were > 32 micrograms/ml for cefpirome and 32 and > 64 micrograms/ml for desacetylcefotaxime.