medical Definition of XDR
- No one knows the exact number of cases of the two types of drug-resistant TB, called MDR and XDR for multidrug-resistant and extensively drug-resistant.
- —Donald G. McNeil Jr., The New York Times, 23 Mar. 2010
- XDR tuberculosis is caused by a strain of Mycobacterium tuberculosis resistant to isoniazid and rifampin (which defines MDR tuberculosis) in addition to any fluoroquinolone and at least one of the three following injectable drugs: capreomycin, kanamycin, and amikacin.
- —Mario C. Raviglione and Ian M. Smith, The New England Journal of Medicine, 15 Feb. 2007