MtrAB two-component system is crucial for the intrinsic resistance and virulence of Mycobacterium abscessus

Mycobacterium abscessus (Mab) poses serious therapeutic challenges, principally due to its intrinsic resistance to a wide array of antibiotics. The pressing issue of drug resistance has spurred an urgent need to explore novel targets and develop new therapeutic agents against Mab. The MtrAB two-component system, conserved among Actinobacteria, is pivotal for regulating various metabolic processes. Nevertheless, the role of MtrAB in Mab remains elusive. In this study, we uncovered that Mab strains with disrupted mtrA, mtrB or both exhibited heightened susceptibility to a variety of antibiotics with diverse mechanisms of action, in contrast to the wild-type strain. In a murine model, rifabutin, bedaquiline, and amikacin, which were inactive against the wild-type Mab strain, demonstrated efficacy against all the mtrA, mtrB and mtrAB knockout strains, significantly reducing pulmonary bacterial burdens compared to vehicle controls after ten days of treatment. Notably, the virulence of all the mtrA, mtrB, and mtrAB knockout strains was highly diminished in the murine model, as evidenced by a substantial decrease in bacterial load in the lungs of mice after 16 days. We observed that all three knockout strains exhibited a significantly reduced growth rate compared to the wild-type strain. We discovered that cells lacking mtrA, mtrB or both exhibited an elongated cell length and had multiple septa, suggesting that both MtrA and MtrB regulate cell division of Mab. Subsequently, an ethidium bromide accumulation assay disclosed that the absence of either mtrA or mtrB or both significantly increased cell envelope permeability. In summary, this study suggests that mtrA and mtrB play an important role in the intrinsic resistance and virulence of Mab by affecting cell division and altering cell permeability. Consequently, MtrA and MtrB represent promising targets for the discovery of anti-Mab drugs.