What is the difference between MDR TB and XDR TB?
Both indicate strains of M. tuberculosis that can be difficult to treat, but XDR TB is resistant to more drug therapies. XDR TB is currently defined by the CDC (Centers for Disease Control and Prevention) and WHO (World Health Organization) as M. tuberculosis that is resistant to isoniazid and rifampin, plus resistant to any fluoroquinolone and to at least one of three injectable second-line drugs (amikacin, kanamycin, or capreomycin). The emergence of XDR TB is being closely watched by the world medical community and measures are being taken in hopes of limiting its spread.
