A sputum isolate from a patient with pulmonary tuberculosis shows resistance to rifampicin and isoniazid plus resistance to any fluoroquinolone. Per WHO definitions, resistance to which additional drug class upgrades this strain from pre-XDR to XDR-TB?
- A Ethambutol or pyrazinamide
- B Amikacin or capreomycin
- C Bedaquiline or linezolid ✓
- D Cycloserine or ethionamide
Correct answer: C. Bedaquiline or linezolid
Explanation
WHO redefined XDR-TB in 2021 as MDR/RR-TB with additional resistance to any fluoroquinolone AND at least one other Group C drug, namely bedaquiline or linezolid. Resistance to amikacin or capreomycin defined the older injectable-based XDR definition, which is obsolete. Ethambutol and pyrazinamide are first-line drugs already part of MDR context, and cycloserine and ethionamide are Group A agents not used in the XDR definition.
Reference: WHO Consolidated Guidelines on Tuberculosis, Drug-Resistant Tuberculosis Treatment, 2022 update ed.
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Written and medically reviewed by the StethoPrep medical team.