Abstract
The in vitro activities of two-drug combinations of aztreonam, ciprofloxacin, and ceftazidime were studied in 96 clinical isolates of Pseudomonas aeruginosa and in 20 clinical isolates of Pseudomonas cepacia from cystic fibrosis patients. Some synergy was observed with each combination used against P. aeruginosa, but synergy was rare when the combinations were used against P. cepacia.