ABSTRACT
OBJECTIVES: Finafloxacin is an investigational fluoroquinolone exhibiting broad-spectrum activity that is enhanced under slightly acidic conditions (pH 5.0-6.5). The impact of individual and combinations of chromosomal mutations (gyrA, parC and marR) and the plasmid-mediated fluoroquinolone resistance mechanisms QepA1, QnrA1, QnrB1, QnrS1 and AAC(6')-Ib-cr were investigated. METHODS: The MICs of finafloxacin, compared with those of ciprofloxacin, levofloxacin and moxifloxacin, were determined at pH 5.8 and 7.2. RESULTS: MICs of finafloxacin compared with other fluoroquinolones at pH 5.8 were lower by a factor of 2-256. MICs of finafloxacin were unaffected by QepA1. Moreover, finafloxacin appeared not to be a substrate for AAC(6')-Ib-cr. CONCLUSIONS: Compared with ciprofloxacin, levofloxacin and moxifloxacin, finafloxacin shows higher activity especially at pH 5.8 against Escherichia coli mutants expressing known fluoroquinolone resistance determinants alone and in combinations.
