Transcriptomic Profiling of Efflux Pump Genes in Mycobacterium tuberculosis Under Linezolid Stress
In this study, we investigated the role of efflux pump genes in linezolid resistance. M. tuberculosis H37Rv cultures were exposed to sub-inhibitory concentrations of linezolid (¼ MIC) for 24 hours, and transcriptomic analysis was performed to identify upregulated genes. Of the 120 genes involved in cell wall processes, 9/120 (7.5%) were efflux pump genes, primarily belonging to the ATP-binding cassette (ABC), major facilitator superfamily (MFS), resistance nodulation division (RND), and small multidrug resistance (SMR) families. qRT-PCR, performed at 1/2, 1/4 and 1/8 MIC of linezolid, confirmed the RNA-seq results, showing that 8/9 (88.88%) of the efflux pump genes were upregulated at 1/8 MIC of linezolid, indicating that this concentration is optimal for studying efflux pump activity. These findings not only identify 1/8  MIC as optimum concentration for efflux pump studies after linezolid exposure, they also highlight the significant role of efflux pumps in linezolid resistance, providing potential targets for further research on efflux pumps in clinical isolates of M. tuberculosis. Overall design: This study aimed to identify efflux pump genes influenced by linezolid exposure through transcriptomic analysis. Cultures of M. tuberculosis H37Rv were exposed to delamanid at a sub-inhibitory concentration of 1/4 MIC for 24 hours and transcriptomic sequencing was performed on exposed and unexposed cultures.