Asked by Pranav
Mycobacterium tuberculosis is intrinsically resistant to many antibiotics, limiting the number of compounds available for treatment. This intrinsic resistance is due to a number of mechanisms including a thick, waxy, hydrophobic cell envelope and the presence of drug degrading and modifying enzymes.
Also, with antitubercular therapy, mycobacteria are hard to kill because dormant cells exist even in patients with active disease and these cells are far less susceptible to antibiotics than metabolically active bacteria.