Postantibiotic effect of a combination of antimicrobial agents on Pseudomonas aeruginosa

Treatment of severe Pseudomonas infections often calls for multidrug therap y. Combinations of aminoglycosides, beta-lactams and/or quinolones are gene rally administered, the effect of which may be additive, synergistic or ind ifferent. The present in vitro study was designed to find out the exact out come of the postantibiotic effect (PAE), The minimal inhibitory concentrati ons and the PAE of three antibiotics (amikacin, ceftazidime and ciprofloxac in) were determined both singly and in combination. Ceftazidime alone exhib ited a negative PAE but a synergistic effect was observed for the combinati on of ceftazidime with amikacin. The combination of ceftazidime with ciprof loxacin and ciprofloxacin with amikacin however gave an indifferent PAE. Th is synergistic PAE of amikacin with ceftazidime has a significant effect on designing optimal dosage regimens. Copyright (C) 2000 S. Karger AG, Basel.