Antimicrobial activity of a new antipseudomonal dual-action drug, Ro 25-0534

Ro 25-0534, a tertiary amine-linked dual action combination (DAC) of a catechol cephalosporin and ciprofloxacin, was compared with a previously described DAC (Ro 23-9424), ciprofloxacin and cefotaxime. A total of 688 recent clinical isolates were tested and an additional collection of 110 Gram-negative bacilli possessing documented resistance to broad-spectrum antimicrobials were used. Ro 25-0534 was active against all tested species of Enterobacteriaceae (MIC90 range, 0.06-2 micrograms/ml), oxacillin-susceptible staphylococci, beta-hemolytic streptococci, and penicillin-susceptible pneumococci (MIC90 range, 1-2 micrograms/ml). Haemophilus influenzae (MIC90 range, 0.25-0.5 micrograms/ml), Moraxella catarrhalis (MIC90, 0.5 microgram/ml), and most nonenteric Gram-negative bacilli (MIC90 range, 2-4 micrograms/ml) such as Pseudomonas aeruginosa, Acinetobacter spp., and Xanthomonas maltophilia. Enterococci and Bacteroides fragilis isolates were resistant to Ro 25-0534. The Ro 25-0354 potency against most susceptible strains was generally severalfold less than that of Ro 23-9424 (except for Pseudomonas-Xanthomonas) or ciprofloxacin alone.