MDR-TB is able to thrive in the presence of drugs that would kill a regular TB bacillus. Such strains can be found all over the world.
People often stop taking their medications when they begin to feel better.
This erratic exposure to treatment incompletely kills the bacillus and gives them time to develop mutations that can resist first-line drug treatment. MDR-TB is rising at an alarming rate in some countries, especially the countries of Eastern Europe, and is threatening global TB control efforts. From the perspective of public health, poorly supervised or incomplete treatment of TB is worse than no treatment at all. People infected with TB that is resistant to first-line TB drugs will confer this resistant form of TB to people they infect. MDR-TB is treatable, but it requires treatment for up to 2 years, more careful monitoring and management of treatment, and involves drugs that have a greater risk of toxicity.