Activity of two novel fluoroquinolones (DU-6859a and DV-7751a) tested against glycopeptide-resistant enterococcal isolates.

Two novel fluoroquinolones, DU-6859a and DV-7751a, were compared with three peer compounds (ciprofloxacin, levofloxacin, and ofloxacin) by testing 150 strains of enterococci that were resistant to vancomycin. Standardized methods recommended by the National Committee for Clinical Laboratory Standards were used for all minimum inhibitory concentration tests, and DU-6859a was additionally tested by the standardized disk diffusion procedure (5-mu g disks). The rank order of the fluoroquinolone spectrums against these Enterococcus spp. isolates was DU-6859a (71.3% of strains inhibited at < or = 2 mu g/ml) > DV-7751a (38.7%) > levofloxacin (33.3%) > ofloxacin (32.0%) > ciprofloxacin (3.3%). Using previously proposed break point zone diameters of > or = 16 mm (susceptible) and < or = 12 mm (resistant), the DU-6859a disk diffusion tests for these glycopeptide-resistant organisms were without false-susceptible or false-resistant error (81.3% absolute agreement). These results indicate that among the investigational and currently marketed fluoroquinolones, DU-6859a appears to have the greatest potential value in the therapy of Enterococcus spp. strains that are resistant to the glycopeptides and many other therapeutic agents.