Post-antibiotic and synergic effects of fluoroquinolones and ceftazidime in combination against Pseudomonas strains

Infectious complications are still the leading cause of morbidity and morta lity in seriously ill patients [1-3]. To combat the resistance of (mainly G ram-negative, non-fermentative) bacteria, e.g. Pseudomonas aeruginosa, to a wide spectrum of antibiotics, drug combination therapy has been widely ado pted as standard clinical practice since the late 1990s. beta -Lactam combi nations are not optimal and the potential of nephrotoxicity and ototoxicity from aminoglycosides has caused clinicians to evaluate new possibilities, such as combinations of fluoroquinolones and beta -lactams. We examine here the synergic and post- antibiotic effects (PAEs) of ciprofloxacin, ofloxac in and pefloxacin-ceftazidime combinations against 6 clinical Pseudomonas i solates. The fluoroquinolone-ceftazidime combinations were not only synergic against Comamonas (P). testosteroni, but had double the PAEs of the two drugs alon e. The ciprofloxacin-ceftazidime combination had a longer PAE against P. ae ruginosa isolate 1 than ciprofloxacin alone. The combinations, however, did not have longer PAEs than those of the single drugs against the other 5 P. aeruginosa isolates.