Mutations in the MAB_2299c TetR Regulator Confer Cross-Resistance to Clofazimine and Bedaquiline in .

New therapeutic approaches are needed against , a respiratory mycobacterial pathogen that evades efforts to successfully treat infected patients. Clofazimine and bedaquiline, two drugs used for the treatment of multidrug-resistant tuberculosis, are being considered as alternatives for the treatment of lung diseases caused by With the aim to understand the mechanism of action of these agents in , we sought herein to determine the means by which can develop resistance. Spontaneous resistant strains selected on clofazimine, followed by whole-genome sequencing, identified mutations in , encoding a putative TetR transcriptional regulator. Unexpectedly, mutants with these mutations were also cross-resistant to bedaquiline. MAB_2299c was found to bind to its target DNA, located upstream of the divergently oriented gene cluster, encoding MmpS/MmpL membrane proteins. Point mutations or deletion of was associated with the concomitant upregulation of the and transcripts and accounted for this cross-resistance. Strikingly, deletion of and in the mutant strain restored susceptibility to bedaquiline and clofazimine. Overall, these results expand our knowledge with respect to the regulatory mechanisms of the MmpL family of proteins and a novel mechanism of drug resistance in this difficult-to-treat respiratory mycobacterial pathogen. Therefore, may represent an important marker of resistance to be considered in the treatment of diseases with clofazimine and bedaquiline in clinical settings.