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Mycobacterium xenopi — SCE Infectious Diseases MCQ

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HardTuberculosisMycobacterium xenopiSCE Infectious Diseases

A 55-year-old man presents with chronic cough, weight loss, and a single cavitating lung lesion. Sputum is smear-negative for AFB but culture grows an organism identified as Mycobacterium xenopi. He is immunocompetent. CT shows a thin-walled cavity in the right upper lobe. What is the recommended treatment?

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Correct answer: C — Rifampicin, Ethambutol, and a macrolide (Clarithromycin) daily; consider adding Isoniazid or a Fluoroquinolone; treatment for 12 months post culture conversion

M. xenopi is a NTM that can cause pulmonary disease, particularly in patients with underlying lung disease. BTS/ATS guidelines recommend combination therapy including Rifampicin, Ethambutol, and a macrolide (Clarithromycin or Azithromycin), with consideration of adding Isoniazid or Moxifloxacin. M. xenopi has relatively high mortality rates compared to other NTM. Treatment should continue for 12 months beyond the last positive sputum culture. Unlike M. kansasii, M. xenopi does not reliably respond to Isoniazid alone.

Reference: BTS 2017 – NTM pulmonary disease; ATS/IDSA 2020 – NTM guidelines