Cross-resistance analysis for DU-6859a, a new fluoroquinolone, compared to six structurally similar compounds (ciprofloxacin, clinafloxacin, fleroxacin, levofloxacin, ofloxacin, and sparfloxacin).

Emerging resistance to the current fluoroquinolones has encouraged synthesis of new compounds in this class. We have evaluated the activity of DU-6859a, a novel halogenated quinolone, against a panel of 300 bacteria, relative to the activity of ciprofloxacin, clinafloxacin, fleroxacin, levofloxacin, ofloxacin, and sparfloxacin. DU-6859a was the most active of the fluoroquinolones studied and retains potentially useful activity against 80% of isolates resistant (minimum inhibitory concentration, > or = 4 micrograms/ml) to ciprofloxacin. Continued clinical investigation of DU-6859a and similar new quinolones is urged.