ABSTRACT
Objective/background: Detection of mutations in the quinolone resistance-determining region [QRDR] of the gyrA gene could determine resistance to fluoroquinolone antitubercu-losis 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 QRDR region 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 codons in resistant isolates of the two countries [P < .001]. There was no polymorphii observed in codon 95 in any of the ofloxacin-susceptible isolates
Conclusion: It was concluded that the determination of nucleotide sequences of QRE can be used as a molecular test for the rapid detection of ofloxacin resistance. Furthermc frequencies in gyrA codons in Belarus and Iran were similar, therefore it is not of geograj ical concern for the two countries