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 agai nst Pseudomonas aeruginosa biofilms by employing an in vitro model of cathe ter-associated infection because such infections are refractory to antimicr obial 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 c atheter in artificial urine. The colony-forming activities of biofilm bacte ria were determined for 48 hours during the treatment with each drug at con centrations of 1 up to 128 times the minimal bactericidal concentration (MB C), and time-kill curves were constructed by plotting the viable cell count s against time. Results. Although CAZ was more bactericidal to the biofilm bacteria than PI PC, the biofilm bacteria still remained on the catheter during CAZ treatmen t 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 c oncentration 64 and 128 times the MBC, respectively. Both CPFX and LVFX era dicated biofilm bacteria completely by 24 hours at a concentration 32 times the MBC. Conclusions. These results indicate that fluoroquinolones have the most pot ent bactericidal activity against the P. aeruginosa biofilm generated in ur ine. UROLOGY 53: 1058-1062, 1999. (C) 1999, Elsevier Science Inc. All right s reserved.