XDR-TB stands for Extensively Drug Resistant TB (also referred to as Extreme Drug Resistance). This is MDR-TB that has also become resistant to three or more of the six classes of second-line drugs.
The description of XDR-TB was first used earlier in 2006, after a survey by the World Health Organisation and the US Centres for Disease Control and Prevention.
XDR-TB is a serious global concern as there are limited treatment options available for people infected with these strains. Newer drugs e.g. Bedaquiline, Delaminid and Linezolid are showing potentially better clinical outcomes in these patients with shorter duration of treatment. However, further evaluation is needed.
XDR-TB is especially worrisome in areas where the HIV prevalence is high, because it is extremely difficult to treat in HIV-positive people. The WHO reported and estimated 9% of all MDR TB to be XDR TB (2013). The current figure in South Africa is currently unknown but is suspected to be between 5–10% of MDR TB cases.
Reviewed by Dr AW Dreyer, Pathologist and Clinical Microbiologist, Centre for Tuberculosis, National Institute for Communicable Diseases February 2015.
Previously reviewed by Joanna Evans, PhD, Molecular Mycobacteriology Research Unit, Division of Medical Microbiology Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, February 2011.