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.