Fluoroquinolone resistance in clinical isolates of Klebsiella oxytoca.

BACKGROUND

Prevalence of fluoroquinolone-resistant Klebsiella oxytoca has been reported worldwide.

METHODS

We recovered ten clinical K. oxytoca isolates from patients with acute cystitis, asymptomatic bacteriuria or acute bacillary diarrhea in Japan. Out of ten isolates, one fluoroquinolone-susceptible isolate was included as a control. Fluoroquinolone resistance was characterized genetically by PCR and DNA sequencing methods. Outer membrane protein (OMP) profiles were determined by SDS-PAGE.

RESULTS

In nine clinical isolates of levofloxacin-resistant K. oxytoca, nucleotide sequences in the quinolone-resistance-determining regions showed amino acid mutations such as Thr83Ile and Asp87Gly in GyrA and Ser80Ile in ParC. Combined effects of reduced 36-kDa OMP production and amino acid mutations in GyrA and ParC were shown by two K. oxytoca isolates exhibiting higher minimum inhibitory concentrations for fluoroquinolones than other fluoroquinolone-resistant isolates.

CONCLUSIONS

In clinical K. oxytoca isolates, the various mechanisms of fluoroquinolone resistance may include reduced 36-kDa OMP production as well as GyrA and ParC mutations.