In vitro activity of the aerosolized agents colistin and tobramycin and five intravenous agents against Pseudomonas aeruginosa isolated from cystic fibrosis patients in southwestern Germany

Three hundred and eighty-five mucoid and non-mucoid strains of Pseudomonas aeruginosa isolated from 192 sputa from 57 adult cystic fibrosis patients were studied. Susceptibility testing using an agar dilution technique was performed for ceftazidime, ciprofloxacin, fosfomycin, meropenem and piperacillin, and the aerosolized agents colistin and tobramycin. Meropenem, ceftazidime and piperacillin were the most potent agents (susceptibility 86.2%, 84.2% and 84%, respectively). Tobramycin and colistin susceptibility rates were lower, but in light of higher intrabronchial concentrations of these drugs a greater percentage of strains might still be clinically susceptible. Only 46.2% and 41.8% of isolates were susceptible to ciprofloxacin and fosfomycin, respectively.