Drug-resistant tuberculosis.

There is increasing concern in many countries about the problem of drug-resistant tuberculosis, particularly so because no new classes of drugs have been developed for the treatment of tuberculosis since the 1960s. Although drug resistance is thought to be fairly common in some countries and rare in others, the global extent of this condition is not precisely known. This problem is currently being investigated by a combined initiative of the World Health Organization and the International Union Against Tuberculosis and Lung Disease. Recently, there have been advances in the understanding of the genetic basis of drug-resistant tuberculosis. With the sequencing of the whole genome of Mycobacterium tuberculosis, the possibility of new targets for drug development has emerged. For the present, however, cure rates on average remain modest, and nonadherence with chemotherapy remains a major problem. Drug resistance is a man-made problem and efforts to prevent it through directly observed therapy, short course are essential.