The in-vitro activity of CP 99,219, a new naphthyridone antimicrobial agent: a comparison with fluoroquinolone agents.

The in-vitro activity of a new fluoroquinolone, CP 99,219 was compared with that of ciprofloxacin, DU 6859, sparfloxacin and levofloxacin. CP 99,219 showed generally similar in-vitro activity to the other compounds tested against the Enterobacteriaceae (MIC90 of all agents < 0.5 mg/L except Morganella morganii). It was found to be more active than ciprofloxacin, sparfloxacin and levofloxacin against the strains of Acinetobacter calcoaceticus tested (MIC90 1 mg/L). CP 99,219 was found to be four-fold more active against strains of Stenotrophomonas maltophilia than ciprofloxacin (MIC90 1 and 8 mg/L, respectively). Haemophilus influenzae and Neisseria spp. were highly susceptible to all the agents tested. CP 99,219 was more active than ciprofloxacin, sparfloxacin and levofloxacin against Gram-positive organisms, but less active than DU 6859. The enhanced anti-Gram-positive activity of CP 99,219 was most marked against the nine strains of methicillin-resistant Staphylococcus aureus tested. The MIC90 of CP 99,219 of these strains was 1.0 mg/L compared with 64 mg/L for ciprofloxacin. Against Bacteroides fragilis, CP 99,219 (MIC90 0.25 mg/L) and DU 6859 (MIC90 0.03 mg/L) were more active than the other quinolones. Chlamydia spp. were susceptible to < or = 0.12 mg/L of CP 99,219. Mycobacterial strains tested were less susceptible to CP 99,219 than to ciprofloxacin. The protein binding of CP 99,219 was 87.9% at 1 mg/L.