MDR Tuberculosis — Critical Steps for Prevention and Control

ultidrug-resistant (MDR) tuberculosis is defined as disease caused by strains of Mycobacterium tuberculosis that are at least resistant to treatment with isoniazid and rifampicin; extensively drug-resistant (XDR) tuberculosis refers to disease caused by multidrug-resistant strains that are also resistant to treatment with any fluoroquinolone and any of the injectable drugs used in treatment with second-line anti-tuberculosis drugs (amikacin, capreomycin, and kanamycin). MDR tuberculosis and XDR tuberculosis are serious threats to the progress that has been made in the control of tuberculosis worldwide over the past decade. 1,2 In 2008, an estimated 440,000 cases of MDR tuberculosis emerged globally. 1 India and China carry the greatest estimated burden of MDR tuberculosis, together accounting for almost 50% of the world’s total cases. More than three quarters of the estimated cases of MDR tuberculosis occur in previously untreated patients. The proportion of MDR cases among new cases and previously treated cases of tuberculosis reported globally from 1994 through 2009 ranged from 0 to 28.3% and from 0 to 61.6%, respectively (Fig. 1). The highest proportions of MDR cases, and the most severe drug-resistance patterns, appear in the countries of the former Soviet Union. By 2009, a total of 58 countries had reported at least one case of XDR tuberculosis. In eight countries, reported cases of XDR tuberculosis account for more than 10% of all cases of MDR tuberculosis, and six of these countries were part of the former Soviet Union. By far the largest number of cases of XDR tuberculosis has been reported from South Africa (10.5% of all cases of MDR tuberculosis in that country), owing to rapid spread among people infected with the human immunodeficiency virus (HIV). National programs are failing to diagnose and treat MDR tuberculosis. Globally, just under 30,000 cases of MDR tuberculosis were reported to the World Health Organization (WHO) in 2008 (7% of the estimated total), of which less than one fifth were managed according to international guidelines. The vast majority of the remaining cases probably are not diagnosed or, if diagnosed, are mismanaged. This problem remains despite the evidence that management of MDR tuberculosis is cost-effective 3 and that treatment of MDR tuberculosis, and even treatment of XDR tuberculosis, is feasible in persons who are not infected with HIV. 4,5