Effects of mutations in multiple Ethionamide-resistance-associated genes among Mycobacterium tuberculosis clinical isolates from China

TL;DR

This study examines how mutations in specific genes affect resistance to the TB drug ethionamide in Mycobacterium tuberculosis isolates from China.

Contribution

The study identifies novel mutations and their association with high-level ethionamide resistance in clinical isolates from China.

Findings

95.1% of ethionamide-resistant isolates had at least one mutation in ETH resistance-associated genes.

Multiple mutations were significantly linked to high-level resistance (P = 0.012).

Novel mutations like inhA -100C>A and mshA Tyr155Ser were detected in resistant strains.

Abstract

The growing burden of drug-resistant tuberculosis (TB) constitutes a major public health challenge. Ethionamide (ETH), a second-line anti-TB drug, plays an important role in the treatment of multidrug-resistant tuberculosis (MDR-TB). However, the molecular mechanisms underlying ETH resistance remain incompletely elucidated. Thus, this study aimed to evaluate the effects of mutations in ETH resistance-associated genes (inhA, ethA, ethR, and mshA) on ETH resistance levels among Mycobacterium tuberculosis (MTB) isolates from China.

A total of 137 MTB isolates from China were tested for ETH minimum inhibitory concentrations (MICs) pusing Sensititre® plates, and the sequences of four ETH resistance-associated genes were analyzed based on genomic and PCR sequencing data.

Our results showed that 95.1% (39/41 isolates) of ETH-resistant isolates harbored at least one mutation in these four ETH resistance-associated genes. Most mutations were found in the inhA and ethA (including 5’ untranslated region). Mutations in inhA region were mainly concentrated at the -777C>T site, whereas those in the ethA region were relatively scattered. Notably, multiple mutations were common in high-level ETH-resistant strains and were significantly associated with high-level resistance (P = 0.012). Furthermore, several novel single mutations in ETH-resistant strains, including inhA -100C>A, ethA -31G>A, and mshA Tyr155Ser, were detected.

Different individual mutations and multiple concurrent mutations in ETH resistance-associated genes are associated with varying levels of ETH resistance. These results broaden our understanding of the molecular characteristics of ETH resistance in China.