Multidrug-resistant tuberculosis.

In 1993, the World Health Organization declared tuberculosis a global emergency. Tuberculosis is the leading cause of death attributable to a single infectious pathogen. One-third of the world's population are at risk of developing the disease. In countries confronted with the human immunodeficiency virus (HIV) epidemic, the overlap of these two populations leads to a rapid acceleration of active tuberculosis and of the emergence of multidrug-resistant tuberculosis. Multidrug-resistant tuberculosis is defined as isolates resistant to both isoniazid and rifampicin with or without resistance to other antituberculosis drugs. In the United States, outbreaks of multidrug-resistant tuberculosis have been reported in patients with HIV infection and acquired immunodeficiency syndrome (AIDS) as well as HIV sero-negative patients. These reports have caused great concern owing to the very high case-fatality rate. The treatment outcome of multidrug-resistant tuberculosis is poor. The use of second-line drugs is frequently associated with toxicity and intolerance. Patients require admission to hospitals at the beginning of treatment and adjunctive resectional surgery should be considered when the sputum does not convert after 4 months of therapy. The incidence of multidrug-resistant tuberculosis among Singapore residents remains low. Organisms resistant to one drug occurred in 3.8% of newly diagnosed tuberculosis cases with positive culture and 8.7% of relapsed tuberculosis cases with positive cultures. Organisms resistant to two or more drugs occurred in 1.6% of newly diagnosed culture positive tuberculosis cases and 4.6% of relapsed cases where cultures were positive. This is the result of vigilant surveillance, effective treatment including supervised chemotherapy and close monitoring for non-compliance.