The primary reason for the use of drug combination in the treatment of tuberculosis is
Ref-KDT 6/e p745 The bacteria that cause tuberculosis (TB) can develop resistance to the antimicrobial drugs used to cure the disease. Multidrug-resistant TB (MDR-TB) is TB that does not respond to at least isoniazid and rifampicin, the 2 most powerful anti-TB drugs. ... In some cases even more severe drug-resistant TB may develop.