Mycobacterium abscessus is an emerging human pathogen leading to significant morbidity and even mortality, intrinsically resistant to almost all the antibiotics available and so can be a nightmare. Mechanisms of its intrinsic resistance remain not fully understood. Here, we selected and confirmed an M. abscessus transposon mutant that is hypersensitive to multiple drugs including rifampin, rifabutin, vancomycin, clofazimine, linezolid, imipenem, levofloxacin, cefoxitin, and clarithromycin. The gene MAB_0189c encoding a putative arabinosyltransferase C was found to be disrupted, using a newly developed highly-efficient strategy combining next-generation sequencing and multiple PCR. Furthermore, selectable marker-free deletion of MAB_0189c recapitulated the hypersensitive phenotype. Disruption of MAB_0189c resulted in an inability to synthesize lipoarabinomannan and markedly enhanced its cell envelope permeability. Complementing MAB_0189c or M. tuberculosis embC restored the resistance phenotype. Importantly, treatment of M. abscessus with ethambutol, a first-line antituberculosis drug targeting arabinosyltransferases of M. tuberculosis, largely sensitized M. abscessus to multiple antibiotics in vitro. We finally tested activities of six selected drugs using a murine model of sustained M. abscessus infection and found that linezolid, rifabutin, and imipenem were active against the MAB_0189c deletion strain. These results identified MAB_0189 as a crucial determinant of intrinsic resistance of M. abscessus, and optimizing inhibitors targeting MAB_0189 might be a strategy to disarm the intrinsic multiple antibiotic resistance of M. abscessus. IMPORTANCE Mycobacterium abscessus is intrinsically resistant to most antibiotics, and treatment of its infections is highly challenging. The mechanisms of its intrinsic resistance remain not fully understood. Here we found a transposon mutant hypersensitive to a variety of drugs and identified the transposon inserted into the MAB_0189c (orthologous embC coding arabinosyltransferase, EmbC) gene by using a newly developed rapid and efficient approach. We further verified that the MAB_0189c gene played a significant role in its intrinsic resistance by decreasing the cell envelope permeability through affecting the production of lipoarabinomannan in its cell envelope. Lastly, we found the arabinosyltransferases inhibitor, ethambutol, increased activities of nine selected drugs in vitro. Knockout of MAB_0189c made M. abscessus become susceptible to 3 drugs in mice. These findings indicated that potential powerful M. abscessus EmbC inhibitor might be used to reverse the intrinsic resistance of M. abscessus to multiple drugs.
Keywords: MAB_0189c; Mycobacterium abscessus; intrinsic resistance; permeability.