In vitro activity of combination therapy with cefepime, piperacillin-tazobactam, or meropenem with ciprofloxacin against multidrug-resistant Pseudomonas aeruginosa strains

The prevalence of multidrug-resistant Pseudomonas aeruginosa strains has been increasing every year, and treatment with various antimicrobial combinations has been offered alternatively in the clinical practice. The aim of this study was to evaluate the in vitro effects of combinations of meropenem, cefepime, or piperacillin-tazobactam with ciprofloxacin against multidrug-resistant P. aeruginosa strains by the time-kill method. The results show that both the combination of two beta lactams with ciprofloxacin and three beta lactams with ciprofloxacin against 4 of 5 multidrug-resistant P. aeruginosa strains has no effect in vitro. The combination of one beta lactam (meropenem, cefepime, piperacillin-tazobactam) with ciprofloxacin has a synergistic effect against one strain of multidrug-resistant P. aeruginosa that is ciprofloxacin susceptible and resistant to meropenem, cefepime, and piperacillin-tazobactam. None of the combinations had an antagonistic effect against these multidrug-resistant strains.