The relevance of Mycobacterium tuberculosis isoniazid-resistance and mutations in two different regions of the katG gene / 中华检验医学杂志

ABSTRACT

Objective To analyze and compare the mutations in two different regions of the katG gene and study the relevance of Mycobacterium tuberculosis isoniazid-resistance and mutations in two different regions of the katG gene. Methods Fifty-three INH-resistant Mycobacterium tuberculosis strains isolated in cultures of sputum samples obtained from Zhejiang province were analyzed. PCR was used to amplify two regions of the katG gene (GenBank accession no. U06258) region 1 (from codon 1 to codon 150) and region 2 ( from codon 227 to codon 470) which were then sequenced in order to identify mutations. Results Three strains resistant to INH did not contain mutations in either region. Fourteen strains carried mutations in region 1. Among them 5 strains barbered deletions, and showed high-level resistance to isoniazid. Five strains had mutations only in region 1. Region 2 carried multiple point mutations, especially at codon 315, and there were S315 N ( AGC→AAC ) substitution in 18 of those cases. The frequency of mutations in the katG S315 of high-level INH-resistance isolates ( 84. 4%, 27/32) was significantly higher than those of low-level INH-resistance isolates( 15.6%, 5/32 ), there was statistically significant difference (x2 = 30. 25, P ＜ 0. 01 ).katG S315 mutations in high-level INH-resistance frequency (84. 4%, 27/32) was significantly higher than the other mutations of katG gene of high-level INH-resistance frequency (27. 7%, 5/18 ), there was significant difference (x2 = 16.02, P ＜ 0. 01 ). The analysis of region 2 allowed INH resistance to be diagnosed in 84. 9% of the strains. Five strains had mutations only in region 1 ,which allowed the proportion of INH-resistant strains identified to be increased to 94. 3%. Conclusions The number of mutations at codon 315 was high. Mutation type and location closely related with drug resistance and the analysis of region 1 resulted in a 9. 4% increase in the rate at which mutations were identified.