Extensively Drug-Resistant Tuberculosis (XDR-TB)

XDR-TB is defined as resistance to at least rifampicin and isoniazid from among the first-line anti-TB drugs (which is the definition of MDR-TB) as well as resistance to any fluoroquinolone, and to at least one of three injectable secondline anti-TB drugs used in TB treatment (capreomycin, kanamycin, and amikacin). Furthermore, in some places XDR-TB has emerged that has shown complete resistance to all anti-TB drugs tested, a virtually untreatable form of TB. XDR-TB can develop when second-line drugs are misused or mismanaged and therefore also become ineffective. Because XDR-TB is resistant to first- and second-line drugs, treatment options are significantly limited. It is therefore vital that XDR-TB is managed properly. XDR-TB has emerged worldwide as a threat to public health and TB Control with notified cases in 100 countries as of 2013, raising concerns of a future epidemic of virtually untreatable TB.

Although there are currently two promising new anti-TB drugs that are beginning to be introduced on a limited scale, additional new anti-TB drug regimens, earlier diagnosis of drug resistance, better diagnostic tests, and international standards for second-line drug-susceptibility testing are urgently needed for effective detection and treatment of MDR-TB and XDR-TB.