Tuberculosis strains classified as multidrug-resistant (MDR) are those resistant to at least the two most potent first-line antituberculosis drugs—ie, isoniazid and rifampicin. When the TB bacteria no longer respond to the first line TB medicines, the only drugs left are less effective, have many more side effects, and are much more expensive. Because it is more difficult to cure, MDR-TB has a much higher mortality rate. Furthermore, if MDR-TB is not treated effectively, patients stay infectious. Like the usual forms of TB, MDR-TB spreads through the air. If MDR-TB is not treated, MDR-TB patients continue to spread these most deadly strains to their family members and communities.
Since 2006 Mongolia has started to implement project on multi-drug resistant TB management through support of the Global Fund to Fight AIDS, Tuberculosis and Malaria. This project helped substantially improve detection of MDR-TB and expand treatment for MDR-TB patients. According to the national drug resistance survey conducted in 2007 MDR-TB was found to be 1.4% among new TB cases and 27.8% among re-treatment cases.