Multi-drug-resistant tuberculosis (MDR-TB, also known as Vank's Disease) is defined as a form of TB infection caused by bacteria that are resistant to treatment with at least two of the most powerful first-lineanti-TB drugs,isoniazid (INH) and rifampicin (RMP).
Five percent (5%) of all TB cases across the globe in 2013 were estimated to be MDR-TB cases, including 3.5% of newly diagnosed TB cases, and 20.5% of previously treated TB cases. While rates of MDR-TB infections are relatively low in North America and Western Europe, they are an increasingly serious problem worldwide, in particular in areas of the Russian Federation, the former Soviet Union and other parts of Asia.
MDR-TB infection may be classified as either primary or acquired. Primary MDR-TB occurs in patients who have not previously been infected with TB but who become infected with a strain that is resistant to treatment. Acquired MDR-TB occurs in patients during treatment with a drug regimen that is not effective at killing the particular strain of TB with which they have been infected. Rates of primary MDR-TB are low in North America and Western Europe: in the US in 2000, the rate of primary MDR-TB was 1% of all cases of TB nationally. Most cases of acquired MDR-TB are due to inappropriate treatment with a single anti-TB drug, usually INH. This can occur due to a medical provider, such as a doctor or nurse, improperly prescribing ineffective treatment, but may also be due to the patient not taking the medication correctly, which can be due to a variety of reasons, including expense or scarcity of medicines, patient forgetfulness, or patient stopping treatment early because they feel better.