Abstract：Objective To analyze the expression of sigma factor in drug resistance gene mutations of Mycobacterium tuberculosis (MTB), so as to provide a reference for the drug resistance mechanism of tuberculosis. Methods Clinical sputum specimens of outpatients at Tianjin Center for Tuberculosis from 2018 to 2022 were collected. A total of 899 MTB-positive strains were obtained by culture, and 492 phenotypically sensitive strains and 407 phenotypically resistant strains were identified by an in vitro phenotypic drug susceptibility test. Thirty drug-sensitive strains of MTB were randomly selected, and 98 drug-resistant strains with specific resistance phenotypes were chosen; all were subjected to melting curve analysis for detection of drug-resistance gene mutations. The strains were divided into sensitive strains without gene mutation, isoniazid-resistant strains with inhA mutation or katG mutation, rifampicin-resistant strains with rpoB mutation, and multigene mutation-resistant strains with inhA+rpoB mutation or katG+rpoB mutation. The mRNA relative expression of sigma factor was detected by fluorescence quantitative PCR, and the ratio of sigma factor mRNA relative expression between the experimental strain and the standard strain >2 was used to screen for highly expressed sigma factor. The differences in sigma factor mRNA relative expression and high expression rate between drug-resistant gene mutant strains and sensitive strains were analyzed. Results Thirty sensitive strains and 90 drug-resistant strains were included. Among them, there were 16 strains with inhA mutation, 22 strains with katG mutation, 13 strains with rpoB mutation, 15 strains with inhA+rpoB mutation, and 24 strains with katG+rpoB mutation. Compared to the sigma factors of the sensitive strains, the mRNA expression levels of sigG and sigI in inhA-mutated strains, sigF, sigG, sigH, sigI, sigJ, and sigL in katG-mutated strains, and sigF, sigG, sigH, sigJ, and sigL in rpoB-mutated, inhA+rpoB-mutated, and katG+rpoB-mutated strains were significantly higher (all P<0.05). Additionally, the high-expression rates of sigI in inhA-mutated strains, sigF, sigG, sigI, sigJ, and sigL in katG-mutated and inhA+rpoB-mutated strains, and sigF, sigG, sigH, sigJ, and sigL in rpoB-mutated and katG+rpoB-mutated strains were also higher (all P<0.05). Conclusion Compared to sensitive MTB strains, sigI showed higher relative expression of mRNA and high-expression rate in inhA-mutated strains, and sigF, sigG, sigJ, and sigL had higher mRNA relative expression and high-expression rates in katG-mutated, rpoB-mutated, and multi-drug-resistant strains.
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