In-vitro activity of meropenem, a new carbapenem, against multiresistant Pseudomonas aeruginosa compared with that of other antipsendomonal antimicrobials
The novel carbapenem meropenem, which is stable to dehydropeptadase action, was studied in vitro against 173 nosocomial isolates of Pseudomonas aeruginosa derived from pus, expectorated sputum, bronchial secretions, urine or blood of infected patients. Susceptibilities to meropenem, imipenem, ceftazidime, cefotaxime, pipera-cillin, gentamicin, amikacin and ciprofloxacin were determined by the agar dilution technique with an inoculum of 10 4 cfu/spot. The proportion of sensitive isolates with MICs below the breakpoint was highest for meropenem (91% ≤ 8 mg/l); the proportion of sensitive isolates for the remaining antibacterials was as follows: ciprofloxacin 87%≤2 mg/l imipenem 85% ≤ 8 mg/l; ceftazidime 77.5% ≤ 16 mg/l; piperacillin 60% ≤ 64 mg/l; amikacin 44% ≤ 8 mg/l; gentamicin 34% ≤ 4 mg/l and cefotaxime 15% ≤ 16 mg/l. Strains moderately resistant to imipenem (MIC 16–32 mg/l) were mostly sensitive to meropenem, but highly resistant strains (MIC 128–256 mg/l) were invariably resistant (MIC > 128 mg/l) to the new carbapenem.