Multidrug-resistant tuberculosis (MDR-TB): epidemiology, prevention and treatment.

Multidrug-resistant tuberculosis (MDR-TB) is an increasing global problem, with most cases arising from a mixture of physician error and patient non-compliance during treatment of susceptible TB. The extent and burden of MDR-TB varies significantly from country to country and region to region. As with TB itself, the overwhelming burden of MDR-TB is in high-burden resource-poor countries. The diagnosis depends on confirming the drug susceptibility pattern of isolated organisms, which is often only possible in resource-rich settings. There should be a strong suspicion of drug resistance, including MDR-TB, in persons with a history of prior treatment or in treatment failure cases. Treatment in developed countries is expensive and involves an individualized regimen based on drug susceptibility data and use of reserve drugs. In resource-poor settings a WHO retreatment regimen may be used, but increasingly the move is to a directly observed treatment based 'DOTS-plus' regimen in a supported national TB programme. However, even where such treatment is given, the outcome for patients is significantly worse than that for fully susceptible TB and has a much higher cost.