Abstract: Objective  To study katG, inhA and ahpC mutations of Mycobacterium tuberculosis isoniazid-resistant clinical isolates, and their effect on minimum inhibitory concentration (MIC) in vitro.  Methods  Isoniazid-resistant genes of 160 Mycobacterium tuberculosis isoniazid-resistant strains and 40 isoniazid-sensitive strains were detected by gene chip. All samples with different gene mutations were determined and compared MICs of isoniazid.  Results  Of isoniazid-resistant strains, 68.8% （110/160） had katG 315 mutations, the MICs of katG 315 gene mutants （20.20±19.46 μg/ml）was significantly higher than inhA gene mutants （0.73±0.82 μg/ml, t′=10.9171, t′_α=1.9807,P＜0.05）, and significantly lower than katG 315 plus inhA gene mutants （69.33±32.45 μg/ml, t′= 7.164, t′_α= 2.0627, P＜0.05）.  Conclusion  Isoniazid-resistant strains had different gene mutation patterns, different genotypes had different levels of isoniazid resistance, which can provide a reference to the clinical.

Key words: Mycobacterium tuberculosis, Microbial sensitivity tests, Isoniazid, Drug resistance,bacterial