Fluoroquinolone resistance and mutation in gyrA gene in clinical isolates of Klebsiella pnemoniae

Fluoroquinolone resistance has been mainly associated with mutation in gyr and par genes bacteria and specific amino acids alteration in gram negative bacteria. In the present study, urinary tract infection isolates of Klebsiella pneumonia were investigated for fluoroquinolone resistance and mutation patterns of gyrA gene in ciprofloxacin resistant isolates.
In 2014, Susceptibility to fluoroquinolones in 46 isolates of K. pneumoniae was tested by the disc diffusion method whereas broth macrodilution method was used to investigate ciprofloxacin minimum inhibitory concentration. Mutations in the quinolone resistance-determining regions (QRDR) was investigated in chromosomal gyrA gene in quinolone-resistant K. pnemoniae isolates, by PCR amplification of gyrA gene and sequencing.
Out of 46 tested bacteria, ten (21.7%) isolates recognized as fluoroquinolones resistant. Minimum inhibitory concentration of ciprofloxacin for resistant isolates ranged between 64 to 2048 µg/mL. In gyrA gene sequence analyses, 8 (80%) isolates had an amino acid substitution. In six isolates mutation occurred in Asp87 that amino acid alters with Alanine and asparagine. Also Ser83Ile substitution was found in one isolate.
The obtained results demonstrated that gyrA mutation is one of the most important mechanisms of resistance to ciprofloxacin in clinical isolates of K. pneumonia in Rasht.