In vitro activity of a new quinolone, rufloxacin, against nosocomial isolates.

The in vitro activity of rufloxacin (MF 934), a new broad-spectrum fluoroquinolone, was tested against 1,032 gram-positive and gram-negative clinical isolates and compared to that of five other compounds of this class. All quinolones except for ciprofloxacin had limited activity against group A and B streptococci and pneumococci (MIC 90% of 4-64 mg/l) and no activity against enterococci. Most species of the enterobacteriaceae and staphylococci were found to be sensitive to rufloxacin (MIC 90% of 0.5-8 and 2-8 mg/l). Like the other quinolones except for ciprofloxacin, rufloxacin was not active against Pseudomonas aeruginosa. The antibacterial activity of rufloxacin was affected only minimally by an increase in the bacterial inoculum or by alterations in the pH of the medium. In spite of the relatively higher MICs of rufloxacin compared to those of the other quinolones, its favorable pharmacokinetic properties may account for its good clinical efficacy.