Spontaneously occurring staphylococcal mutants resistant to clinically achievable concentrations of ciprofloxacin and temafloxacin.

The frequency of spontaneously occurring mutants resistant to 0.5, 1, 2, 4 and 8 micrograms of temafloxacin or ciprofloxacin per milliliter was documented with four Staphylococcus aureus and four Staphylococcus epidermidis strains. Resistant mutants were recovered at two- to four-fold the MIC of either drug, and they displayed cross-resistance to other fluoroquinolones. Resistance to temafloxacin occurred at frequencies lower than those observed with equal concentrations of ciprofloxacin. Resistance to greater than four-fold the MIC of either drug was not detected (frequencies less than 10(-10).