Isoniazid resistance and related gene mutation of 31 Mycobacterium tuberculosis clinical isolates in Guiyang area

Objective The purpose of this study is to analyze gene mutations related with isoniazid resistance of Mycobacterium tuberculosis in Guiyang area. Methods The katG,inhA,oxyR-aphC gene fragment of M.tuberculosis was amplified and sequenced.These strains included seventeen isoniazid resistant clinical isolates and fourteen isoniazid susceptible clinical isolates.Sequences of these strains were analyzed by CLC FreeWorkbench4.5and BioEdit. ResultsThe mutations of katGgene were found in 16 isoniazid resistant clinical isolates.70.5%(12/17)of drug-resistant strains showed katG315(AGC→ACC)mutation.katG463(CGG→TGG)was found in 11 isoniazid susceptible clinical isolates and 4isoniazid resistant clinical isolates.The mutation rate of this type of mutation in isoniazid sensitive strains and isoniazid resistant strains was 78.6%(11/14)and 23.5%(4/17)respectively.There were no significant difference of this rate between sensitive strains and resistant strains(χ2=6.48,P0.05).Double mutations at two separate loci of katG were detected in 12 isoniazid resistance isolates,including katG315(AGC→ACC)combined with 463(CGG→TGG)in 10 strains,463(CGG→TGG)combined with 299(GGC→AGC)in 1isolate and 463(CGG→TGG)combined with 419(GAC→CAC)in 1isolate.No mutation ininhA was found in this study.G32 Amutation of oxyR-aphCgene was found in 2isoniazid resistant strain. Conclusion The results showed the gene polymorphism of katG,inhA,oxyR-aphCin M.tuberculosis.katG315 is the dominant gene mutation related with isoniazid resistant M.tuberculosis in Guiyang.