In vitro activity of Ro 23-9424, a dual-action antibacterial agent, against bacterial isolates from cancer patients compared with those of other agents

The in vitro activity of Ro 23-9424 against bacterial isolates from patients with cancer was compared with those of fleroxacin, ciprofloxacin, cefoperazone, and ceftazidime. Ro 23-9424 inhibited the majority of the members of the family Enterobacteriaceae and all Aeromonas isolates at a concentration of ≤1.0 μg/ml. It was also active against Acinetobacter spp. and Haemophilus influenzae, including β-lactamase-producing strains. The MIC for 90% of isolates (MIC₉₀) of Pseudomonas aeruginosa was 16.0 μg/ml. All group A and B streptococci were inhibited by ≤0.25 μg/ml, and 90% of group G streptococci and Streptococcus pneumoniae were inhibited by 1.0 μg/ml. All methicillin-susceptible strains of Staphylococcus aureus and 60% of methicillin-resistant strains were susceptible to 2.0 μg of Ro 23-9424 per ml, whereas the MIC₉₀ for Staphylococcus epidermidis and Staphylococcus hominis isolates was 4.0 μg/ml. Staphylococcus haemolyticus and Enterococcus spp. were less susceptible; MIC₉₀s for them were 16.0 and 32.0 μg/ml. Ro 23-9424 has a broad antibacterial spectrum and potential utility for therapy of infections in cancer patients.