Abstract:

Objective To determine the gene mutation profile for rifampicin and isoniazid resistance in Mycobacterium tuberculosis (MTB), and explore its relationship with drug resistance level, provide theoretical basis for the development of molecular drug resistant diagnostic tools to inform clinical decision. Methods MTB strains were collected from Xinjiang Uygur Autonomous Region (Keping, Yuepuhu and Shule county, 193 isolates) and Hunan province (Huaihua, Yongshun, Qidong, Taojiang and Leiyang county, 592 strains). Minimum inhibitory concentration (MIC) method was used to determine rifampicin and isoniazid resistant level. All drug resistant strains were sequenced with whole genome sequencing (WGS), then TB profiler were used for bioinformatics analysis to identify drug resistance mutations. Results Among the 785 MTB strains, 124 (15.80%) were rifampicin/isoniazid resistant isolates, including 74 rifampicin-resistant, 111 isoniazid resistant and 61 multidrug-resistant strains, the multidrug-resistant rate was 7.77%. rpoB gene mutations were detected in 97.22% (70/72) of rifampicin resistance strains, among which 98.75% (69/70) mutations were located in rifampicin resistance determination region (RRDR). The rare mutation associated with rifampicin resistance-I491F (outside the RRDR region) was detected in only one strain. Rifampicin resistance mutations were mainly located in rpoB 450, rpoB 445 and rpoB 435 loci, accounting for 81.43% (57/70), among which rpoB S450L was the most frequent mutation (45.71%, 32/70). rpoB 450 mutation corresponded to high rifampicin resistance (MIC≥16 μg/ml), rpoB 452 mutation mainly corresponded to low rifampicin resistance (MIC=2 μg/ml). For isoniazid resistance strains, 93.58% (102/109) had known drug-resistant related gene mutations, mainly distributed in katG315 and fabG1 promoter region (85.29%, 87/102). KatG S315T was the most common resistance mutation (57.84%, 59/102), mainly corresponding to high isoniazid resistance (MIC≥2 μg/ml), followed by fabG1 (C15T)(16.67%, 17/102) which mainly corresponded to low isoniazid resistance (MIC=0.25-1.00 μg/ml). Conclusion Different drug resistance mutations can cause different degree of drug resistance. For rifampin, the mutation in rpoB 452 corresponded to low level resistant, while the mutations in rpoB 445 and 450 corresponded to high level resistant. For isoniazid, fabG1 C-15T corresponded to low level resistant and the mutation in katG 315 corresponded to high level resistant.

Key words: Tuberculosis,multidrug resistance, Microbial sensitivity tests, Gene, Rifampin, Isoniazid