Nontuberculous mycobacteria


  • Characteristics
    • Acid-fast bacilli: Ziehl-Neelsen stain
  • Mycobacterium avium complex (MAC)
    • Most common NTM pathogen.
    • Disseminated Disease (Immunocompromised)
      • Classic in HIV pts with CD4 count < 50 cells/mm³.
      • Sx: Systemic “wasting” syndrome (fever, night sweats, weight loss), diarrhea, hepatosplenomegaly, lymphadenopathy.
      • Dx: Anemia, ↑ Alk Phos, ↑ LDH. AFB smear and blood culture are key.
      • Tx: Clarithromycin or Azithromycin + Ethambutol. Rifabutin often added.
      • Prophylaxis: Azithromycin weekly for HIV pts with CD4 < 50.
    • Pulmonary Disease (Immunocompetent)
      • Presents similarly to TB (cough, fatigue, hemoptysis).
      • Can cause cavitary lesions, often in pts with underlying COPD.
      • “Lady Windermere Syndrome”: Bronchiectasis and nodular infiltrates in the R middle lobe/lingula, classically in elderly, thin women who chronically suppress their cough reflex.
  • M. marinum
    • Fish tank granuloma: skin infection usually of the hand that occur in individuals handling fish (e.g., aquarium handlers)
  • M. scrofulaceum
    • Cervical lymphadenitis in children