In vitro bactericidal activities of beta-lactamases, amikacin, and fluoroquinolones against Pseudomonas aeruginosa biofilm in artificial urine

Objectives. To compare bactericidal activities of antimicrobial agents against Pseudomonas aeruginosa biofilms by employing an in vitro model of catheter-associated infection because such infections are refractory to antimicrobial treatment. Methods. Bactericidal activities of piperacillin (PIPC), ceftazidime (CAZ), panipenem (PAPM), amikacin (AMK), ciprofloxacin (CPFX), and levofloxacin (LVFX) were examined against a P. aeruginosa biofilm generated on a Teflon catheter in artificial urine. The colony-forming activities of biofilm bacteria were determined for 48 hours during the treatment with each drug at concentrations of 1 up to 128 times the minimal bactericidal concentration (MBC), and time-kill curves were constructed by plotting the viable cell counts against time. Results. Although CAZ was more bactericidal to the biofilm bacteria than PIPC, the biofilm bacteria still remained on the catheter during CAZ treatment at a concentration 128 times the MBC for 48 hours, Biofilm bacteria were completely eradicated within 48 hours by treatment with PAPM and AMK at a concentration 64 and 128 times the MBC, respectively. Both CPFX and LVFX eradicated biofilm bacteria completely by 24 hours at a concentration 32 times the MBC. Conclusions. These results indicate that fluoroquinolones have the most potent bactericidal activity against the P. aeruginosa biofilm generated in urine. UROLOGY 53: 1058-1062, 1999. (C) 1999, Elsevier Science Inc. All rights reserved.