In vivo selection of Klebsiella pneumoniae strains with enhanced quinolone resistance during fluoroquinolone treatment of urinary tract infections

Abstract

We report two cases of failure of fluoroquinolone treatment of urinary tract infections with Klebsiella pneumoniae strains harboring quinolone resistance-associated alterations in GyrA and ParC and in vivo selection of posttreatment isolates with enhanced fluoroquinolone resistance. Active efflux leading to decreased accumulation of a drug enhanced fluoroquinolone resistance in one posttreatment isolate, and an additional mutation in parc resulting in an additional amino acid change in ParC was associated with increased resistance in the other.