COMPARATIVE IN-VITRO INTERACTIONS OF CEFTAZIDIME, MEROPENEM, AND IMIPENEM WITH AMIKACIN ON MULTIRESISTANT PSEUDOMONAS-AERUGINOSA

To evaluate the possibility of an enhanced killing effect by ceftazidi me, meropenem, or imipenem with amikacin 26 multiresistant Pseudomonas aeruginosa isolates, to nine antipseudomonal antimicrobials of divers e chemical classes were studied. A modified time-kill curve procedure was used with a 16 mu g/ml concentration of each antimicrobial, i.e. w ithin the range of their serum level; a total of 248 killing-curves we re performed. Any greater than or equal to 2 log(10) decrease of viabl e cell counts by a combination compared to the most active single agen t was considered an adequate enhanced killing effect. The latter was f ound to be mainly expressed at 24 h of growth and involved 30-50% of t he tested isolates. The above findings were independent of the MIC lev el to any individual beta-lactam or to amikacin. It is concluded that there is no difference between the activity of the ceftazidime and ami kacin combination and those of meropenem or imipenem with amikacin on multiresistant P. aeruginosa. (C) 1997 Elsevier Science Inc.