Abstract
The in-vitro activities of four quinolone carboxylic acids against 423 clinical isolates of Gram-negative rods and staphylococci from infected hospitalised patients were compared. The antibiotics included nalidixic acid and the newer compounds, norfloxacin (MK-0366), ciprofloxacin (Bay 09867) and enoxacin (AT 2266 or C1919). Norfloxacin showed slightly more activity than enoxacin, but both agents had markedly greater potencies and broader antibacterial spectrums than nalidixic acid. Ciprofloxacin was the most active quinolone tested against both gentamicin-susceptible and gentamicin-resistant stains, having an MIC90 equal or less than 1 mg/l for all species studied.