Multiple drug resistance: A world-wide threat

The emergence of drug-resistant Mycobacterium tuberculosis threatens the ability of existing health care programmes to treat tuberculosis effectively. Mycobacterium tuberculosis becomes drug resistant primarily through mutations within antituberculosis drug target genes; patient non-compliance with anti- tuberculosis therapy and/or inadequate drug levels promote the selection of these mutations. Drug-resistant tuberculosis can also occur via transmission of an already drug-resistant strain to a susceptible individual. Molecular epidemiology, together with drug sensitivity testing, has shown that transmission accounts for > 50% of the incidence of drug-resistant disease. This demonstrates the inability of current programmes to contain the spread of resistance. The success of future tuberculosis control will depend on a global commitment to directly observed therapy and further research into epidemiology, modern diagnostics and new treatments.