Abstract
Tuberculosis (TB) is an infectious respiratory disease caused by Mycobacterium tuberculosis and one of the top 10 causes of death worldwide. Treating TB is challenging; successful treatment requires a long course of multiple antibiotics. Rifampicin (RIF) is a first-line drug for treating TB, and the development of RIF-resistant M. tuberculosis makes treatment even more difficult. To determine the mechanism of RIF resistance in these strains, we searched for novel mutations by sequencing. Four isolates, CDC-1, CDC-2, CDC-3, and CDC-4, had high-level RIF resistance and unique mutations encoding RpoB G158R, RpoB V168A, RpoB S188P, and RpoB Q432insQ, respectively. To evaluate their correlation with RIF resistance, plasmids carrying rpoB genes encoding these mutant proteins were transfected into the H37Rv reference strain. The plasmid complementation of RpoB indicated that G158R, V168A, and S188P did not affect the MIC of RIF. However, the MIC of RIF was increased in H37Rv carrying RpoB Q432insQ. To confirm the correlation between RIF resistance and Q432insQ, we cloned an rpoB fragment carrying the insertion (encoding RpoB Q432insQ) into H37Rv by homologous recombination using a suicide vector. All replacement mutants expressing RpoB Q432insQ were resistant to RIF (MIC > 1 mg/L). These results indicate that RpoB Q432insQ causes RIF resistance in M. tuberculosis.
Highlights
Mycobacterium tuberculosis is an important human pathogen that causes tuberculosis (TB)
When compared to the sequence of the reference strain H37Rv, in CDC-1, the G at codon 158 was replaced with R (G158R) and the V at codon 170 was replaced with F (V170F)
In CDC2, the V at codon 168 was replaced with A (V168A) and the V at codon 170 was replaced with F (V170F)
Summary
Mycobacterium tuberculosis is an important human pathogen that causes tuberculosis (TB). Over the period of long-term antiTB therapy, M. tuberculosis is exposed to the appropriate drug concentration, which might lead to the development of drugresistant TB and increase the risk of transmission (Yong et al, 2019) It takes at least 6 months to successfully treat TB, and the development of drug resistance makes therapy even more difficult and is a threat to public health. RIF-resistant TB is frequently not adequately treated because of a delay in the diagnosis of drug resistance Such delayed treatment has a poor therapeutic effect on the infected patient and increases the risk of transmission (Boyd et al, 2017; Yong et al, 2019). We examined the effects of novel mutations in known target gene regions and mutations outside of the target region on RIF resistance in M. tuberculosis with the aim to expand upon known RIF resistance-causing mutations for use in clinical molecular diagnostics
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
