CIPROFLOXACIN AND IMIPENEM ALONE OR IN COMBINATION IN EXPERIMENTAL AORTIC-VALVE ENDOCARDITIS DUE TO A CIPROFLOXACIN BORDERLINE SUSCEPTIBLE STRAIN OF PSEUDOMONAS-AERUGINOSA

The in vivo efficacies of ciprofloxacin, imipenem and their combinatio n were studied in the rabbit left-sided endocarditis model by using a seroresistant strain of Pseudomonas aeruginosa with borderline suscept ibilities to ciprofloxacin (MIC/MBC 1/2 and 2/8 mu g/ml to ciprofloxac in and imipenem, respectively). Both antimicrobials expressed synergy in vitro at the MBC level. Ciprofloxacin was given intramuscularly, 20 mg/kg of body weight q 8 h and imipenem at the same regimen intraveno usly for 9 days. When compared to the controls no significant differen ces were observed among the applied regimens regarding (1) blood cultu re sterilization, (2) percent of sterile vegetation, and (3) mean bact erial titers in vegetations. No strain isolated from vegetations at th e end of therapy had developed resistance to either ciprofloxacin or i mipenem. It is concluded that further studies are required after appro priate increase of ciprofloxacin dosage and more frequent administrati on and/or even higher doses of imipenem.