Comparative in vitro activity of DU-6859a, a new fluoroquinolone agent, against gram-positive cocci.

The in vitro activity of DU-6859a (DU), a new fluoroquinolone agent, was evaluated against 233 gram-positive cocci and was compared with those of ciprofloxacin, vancomycin, nafcillin, and ampicillin. The MICs of DU for 90% of the staphylococci tested were < or = 0.06 microgram/ml. All of the groups A and B and viridans group streptococci were inhibited by < or = 0.125 microgram of DU per ml, which was 32-fold more active than ciprofloxacin. On the basis of MICs for 90% of the strains tested, DU was 32- and 16-fold more active than ciprofloxacin against Enterococcus faecalis and Enterococcus faecium, respectively. The bactericidal activity of DU was demonstrated by time-kill techniques against all ciprofloxacin-susceptible enterococci. DU shows promise for the treatment of infections with gram-positive cocci and warrants further evaluation by in vitro and in vivo studies.