A 28-year-old HIV-negative man with fever, productive cough, night sweats, and weight loss has sputum Xpert MTB/RIF positive with rifampicin resistance detected. SLID-DST reveals resistance to fluoroquinolones. According to the 2022 WHO guidelines, this strain is classified as:
- A MDR-TB
- B Pre-XDR TB
- C TDR-TB
- D XDR-TB (2021 revised WHO definition) ✓
Explanation
The 2021 WHO revised definition of XDR-TB (extensively drug-resistant TB) is TB with resistance to rifampicin + any fluoroquinolone + at least one of the Group A drugs for XDR (bedaquiline or linezolid). The older definition required resistance to injectable agents; under the 2021 revision, fluoroquinolone resistance + rifampicin resistance alone meets XDR criteria if bedaquiline or linezolid resistance is also present. However, Pre-XDR TB is defined as MDR/RR-TB + resistance to any fluoroquinolone. Purely fluoroquinolone-resistant RR-TB without bedaquiline/linezolid resistance is pre-XDR. The question states rifampicin resistance + fluoroquinolone resistance = pre-XDR TB under 2021 WHO classification.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.