Causes of drug-resistant tuberculosis Tuberculosis is a chronic infectious disease transmitted through the respiratory tract and is widely prevalent worldwide. Drug-resistant TB occurs when a patient is infected with Mycobacterium tuberculosis that has developed resistance to one or more anti-tuberculosis drugs.WHO reported in 2008 that the total global TB drug resistance rate was 20.0% and the multidrug resistance rate was 5.3%, with an estimated 500,000 cases of multidrug-resistant TB worldwide, of which the 27 countries identified by WHO as having a high burden of drug resistance accounted for 85% of the total number of cases. Drug-resistant TB cases are on the rise, especially with population growth, worldwide travel and increased population mobility, adding approximately 300,000 new cases each year. The epidemic of drug-resistant TB continues to threaten the progress made in TB control, a threat that is exacerbated by the emergence of extensively drug-resistant TB. The emergence of multi-drug resistant TB is mostly man-made: i. Irrational chemotherapy: For example, newly coated positive patients with initial resistance to isoniazid or rifampin are given only 2-3 drugs during the intensification period, resulting in a weak intensification period. During the intensive period, at least 2 sensitive bactericidal drugs, plus 1-2 antibacterial drugs, are generally required to play an effective bactericidal role. Such as the treatment of failure to add a kind of other drugs, or relapse cases to add a single drug, resulting in single-drug chemotherapy, very easy to produce drug resistance. Second, the chemotherapy management is not good: chemotherapy process, the implementation of supervision and management, especially in the intensive period, the patient’s poor compliance, resulting in irregular dosing, interruption of treatment, arbitrary changes in the program, and even premature discontinuation of the drug before the full course of treatment. This is a common and important cause of drug resistance. Third, drug supply problems: poor patients can not get all the anti-tuberculosis drugs they need because of economic reasons or lack of social security; drug-resistant nuclear drugs due to management errors. The shortages are frequent or prolonged due to limited funding in developing countries, and the quality of drugs leads to poor bioavailability of drugs, which affects their efficacy.