What factors have led to multidrug-resistant tuberculosis?

Multidrug-resistant tuberculosis (MDRTB) is defined as combined resistance to isoniazid and rifampin, and can be either primary or acquired. Primary MDRTB occurs in a person who has not previously been treated, whereas acquired MDRTB is a result of treatment failure. The main factors leading to MDRTB include patient noncompliance in drug therapy, inability or unwillingness to find adequate health care, and inappropriate treatment regimens. Homelessness, intravenous drug use, and HIV infection favor the spread of drug-resistant tuberculosis. Resistance is prevalent in Asia, South America, and Africa. In the United States, miniepidemics of drug resistance are centered in New York City, Miami, and Michigan. Spread to health care workers is a major concern. Treatment cure rates of up to 96% have been published in the medical literature, but this requires aggressive and often very complicated management of the disease.