结核杆菌异烟肼表型耐药与katG基因突变相关性研究

Research of the Relationship between Isonazid-resistance and KatG Gene Change

目的:探讨结核分支杆菌异烟肼(INH)表型耐药与KatG基因密码子315位和463位基因改变的相关性。方法:采用基因直接测序法对结核分支杆菌分离株KatG基因进行分析。结果:132株异烟肼耐药菌株中68株KatG基因密码子315位有基因突变,突变率51.52%(68/132),野生型密码子315AGC(Ser)突变成ACC(Thr)60株,AAC(Asn)6株,ACA(Thr)1株,GGC(GIy)1株。133株INH敏感菌株未发现KatG 315位基因突变。132株INH耐药菌株中123株KatG基因密码子463位有基因突变,突变率为93.18%,野生型密码子463CGG(Arg)突变成CTG(Leu)123株;133株敏感菌株中114株KatG基因密码子463位有基因突变,突变率为85.71%,野生型密码子463 CGG(Arg)突变成CTG(Leu)114株。结论:①KatG基因315位密码子突变是菌株异烟肼表型耐药的重要分子基础,以Ser315Thr错义突变为主。②KatG基因463位密码子突变与异烟肼耐药表型没有相关性,不是结核杆菌异烟肼耐药的分子标志。该位点突变可能是基因多态性,与结核菌治疗带来的选择性压力无关。

Objective To investigate the relationship between isonazid-resistance and KatG gene mutation、deletion、insertion.Methods:Analysising the KatG gene of the tuberculosis mycobacterium isolates by Direct sequencing.Results:68 of 132 isonazid-resistant strains had mutation in codon 315 of KatG,The mutation proportion is 51.52%,60 strains had the missense mutation change at codon 315:AGC(Ser)→ACC(Thr),6 strains showed:AGC(Ser)→AAC(Asn),1 strain showed an AGC(Ser)→ACA(Thr),1strains showed an AGC(Ser)→GGC(Gly);there were no gene change at codon 315 of 133 isoniazid-susceptible isolates.A mutation(CGG→CTG)in codon 463 of katG of Mycobacterium tuberculosis has been found,The proportion of isolates with a detectable mutation was 93.18%(123 out of 132) and 85.71%(114 out of 133)among isonizid-resistant and isoniazidsusceptible isolates,respectively.Conclusion:First,our results,in conjunction with those of earlier studies,show that there was a strict relationship between the presence of a mutation at condon 315 and INH resistance of M.tuberculosis isolates,and most mutations are Ser315Thr②Second,the CGG→CTG(Arg463Leu)mutation is not indicative of INH-resistance of a M.tuberculosis,the presence of the CGG→CTG(Arg463Leu)mutation in katG in M.tuberculosis should be considered a polymorphism unrelated to the selective pressure of drug treatment in M.tuberculiosis.