ABSTRACTFluoroquinolone-resistantBurkholderia cepaciamutants were selected on ciprofloxacin. The rate of mutation ingyrAwas estimated to be 9.6 × 10−11mutations per division. Mutations ingyrAconferred 12- to 64-fold increases in MIC, and an additionalparCmutation conferred a large increase in MIC (>256-fold). Growth rate, biofilm formation, and survival in water and during drying were not impaired in strains containing singlegyrAmutations. Double mutants were impaired only in growth rate (0.85, relative to the susceptible parent).