Activity of Meropenem with and without Ciprofloxacin and Colistin against Pseudomonas aeruginosa and Acinetobacter baumannii

Time-kill synergy studies of meropenem combined with ciprofloxacin (A) and colistin (B) against 51 isolates of P. aeruginosa and of meropenem combined with ciprofloxacin (C) and colistin (D) against 41 and 51 strains of A. baumannii, respectively. In each pair of bars, the one on the left represents an additive effect and the one on the right represents synergy. **, Significantly higher percentage of organisms showing synergy (P < 0.001).