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

Abstract

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 possesing documented resistance to broad-spectrum antimicrobials were used. Ro 25-0534 was active against all tested species of Enterobacteriaceae (MIC 90 range, 0.06–2 μg/ml), oxacillin-susceptible staphylococci, β-hemolytic streptococci, and penicillin-susceptible pneumococci (MIC 90 range, 1–2 μg/ml), Haemophilus influenzae (MIC 90 range, 0.25–0.5 μg/ml), Moraxella catarrhalis (MIC 90, 0.5 μg/ml), and most nonenteric Gram-negative bacilli (MIC 90 range, 2–4 μg/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.