Background: Drug-resistant tuberculosis threatens efforts to control the disease. This report describes the prevalence of resistance to four first-line drugs in 35 countries participating in the World Health Organization-International Union against Tuberculosis and Lung Disease Global Project on Anti-Tuberculosis Drug Resistance Surveillance between 1994 and 1997.
Methods: The data are from cross-sectional surveys and surveillance reports. Participating countries followed guidelines to ensure the use of representative samples, accurate histories of treatment, standardized laboratory methods, and common definitions. A network of reference laboratories provided quality assurance. The median number of patients studied in each country or region was 555 (range, 59 to 14,344).
Results: Among patients with no prior treatment, a median of 9.9 percent of Mycobacterium tuberculosis strains were resistant to at least one drug (range, 2 to 41 percent); resistance to isoniazid (7.3 percent) or streptomycin (6.5 percent) was more common than resistance to rifampin (1.8 percent) or ethambutol (1.0 percent). The prevalence of primary multidrug resistance was 1.4 percent (range, 0 to 14.4 percent). Among patients with histories of treatment for one month or more [corrected], the prevalence of resistance to any of the four drugs was 36.0 percent (range, 5.3 to 100 percent), and the prevalence of multidrug resistance was 13 percent (range, 0 to 54 percent). The overall prevalences were 12.6 percent for resistance to any of the four drugs [corrected] (range, 2.3 to 42.4 percent) and 2.2 percent for multidrug resistance (range, 0 to 22.1 percent). Particularly high prevalences of multidrug resistance were found in the former Soviet Union, Asia, the Dominican Republic, and Argentina.
Conclusions: Resistance to antituberculosis drugs was found in all 35 countries and regions surveyed, suggesting that it is a global problem.