Molecular detection of fluoroquinolone resistance-associated gyrA mutations in ofloxacin-resistant clinical isolates of Mycobacterium tuberculosis from Iran and Belarus

摘要

Objective/background: Detection of mutations in the quinolone resistance-determining region (QRDR) of the gyrA gene could determine resistance to fluoroquinolone antituberculosis drugs. The aim of this study was to detect mutations in QRDRs.Methods: From 184 clinical isolates of Mycobacterium tuberculosis, ofloxacin resistance was proven in 42 isolates using the proportion method. The molecular basis of resistance to ofloxacin were investigated by the determination of mutations in the QRDRregion of the gyrA gene. Extracted DNA fragments of 194 bp from the gyrA gene were amplified and an automatic DNA sequencer was used for the sequencing process.Results: Molecular genetic analysis of 42 resistant M. tuberculosis strains demonstrated that they belong to Principal Genetic Group (PGG) 1 in 19 cases (45.2 ± 10.9%), to PGG2 in 15 cases (35.7 ± 10.5%), and to PGG3 in eight cases (19.0 ± 8.4%). Isolates from PGG1 were dominant among resistant isolates (P < .05). It was found that 24 (57%) resistant isolates carried mutations at codon 94 with five different amino acid changes: D94A (n = 11), D94G (n = 3), D94T (n = 4), D94A (n = 4), and D94Y (n = 2). The remaining 18 (43%) isolates had mutations in codon A90V (GCG -> GTG) and S91P (TCG -> CCG). Five isolates had two mutations in codons 90 and 94. There was no difference between mutations at these two