XDR vs. MDR Tuberculosis: Key Differences in Drug Resistance

Both extensively drug-resistant tuberculosis (XDR-TB) and multidrug-resistant tuberculosis (MDR-TB) are forms of TB that resist standard antibiotics, but they differ in the breadth of resistance.

Definitions

• MDR-TB: Resistant to at least the two most potent first-line drugs—isoniazid and rifampicin.
• XDR-TB: Resistant to isoniazid and rifampicin plus any fluoroquinolone and at least one second-line injectable drug (e.g., amikacin, capreomycin, kanamycin). In practice, this means resistance to at least four core drug classes.

Clinical Implications

• Treatment difficulty: XDR-TB has fewer effective drug options, longer regimens, and lower cure rates.
• Transmission risk: XDR-TB strains may survive longer in the environment, potentially increasing person-to-person spread.
• Mortality: XDR-TB carries a higher risk of fatal outcomes if not managed with specialized regimens.

Public Health Importance

Both forms are serious threats. Early detection, drug-susceptibility testing, and adherence to WHO-recommended regimens are critical. If you have TB symptoms—persistent cough, fever, night sweats, weight loss—seek medical care promptly.