Quinolone-resistant phenotype of Flavobacterium columnare isolates harbouring point mutations both in gyrA and parC but not in gyrB or parE.

Objectives: The aim of this study was to determine mutations associated with a quinolone-resistant (QR) phenotype of Flavobacterium columnare isolates.

Methods: The susceptibility of 53 F. columnare isolates to 11 antimicrobials, including 2 quinolones, was investigated by the disk diffusion method.