Abstract: Objective To observe the mutations of gyrA gene in M.Tuberculosis quinolones-resistant isolates,and to evaluate their clinical value.Methods 77 clinical isolates were identified for their mycobacteria species,and were analyzed M.tuberculosis gyrA genes by PCR-SSCP and PCR-direct sequencing.Results Seventy-five isolates were identified as M.tuberculosis.Of 30 quinolones-sensitive isolates,11 isolates had same gyrA SSCP profiles as H₃₇R_v,19 had same profiles as M.bovis BCG.The drug-sensitive isolates whose gyrA SSCP profiles was identical to H₃₇R_v were AGC at condon 95,the others were ACC at condon 95.Of 45 quinolones-resistant isolates,34 (75.6%) displayed abnormal gyrA SSCP profiles.25 clinicals of 2 kinds of gyrA SSCP profiles which appeared at a high frequency were sequenced.15 isolates had GAC→GGC mutation at condon 94;10 isolates had GCG→GTG mutation at condon 90.Conclusion Quinolones resistances in some M.tuberculosis isolates were due to mutation on gyrA genes.PCR-SSCP method might become a simple and rapid diagnostic test for identification of genotypes of M.tuberculosis quinolones-resistance.

Key words: Mycobacterium tuberculosis, Quinolones, Drug-resistance, Polymerase chain reaction, Polymorphism,single-stranded conformational