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Mycobacterium Avium Complex

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Mycobacterium Avium Complex, Mycobacterium Avium Intracellulare, Mycobacterium Avium Complex Infection

  • Epidemiology
  1. Disseminated MAC infection: 40% of North American AIDS
  2. Previously most common reported HIV Bacterial Infection
    1. Early initiation of highly active HIV Antiretrovirals have significantly reduced MAC Incidence
  3. Normal Children may develop Lymphadenitis
    1. Occurs under age 5 years
    2. Rarely affects children over age 12 years
  • Pathophysiology
  1. MAC is ubiquitous in environment (water, soil, food)
  2. Causes Tuberculosis in birds and swine
  3. Colonization by respiratory and gastrointestinal tracts
  4. Rarely occurs if CD4 Count >50
  5. Infection in normal children
    1. Breaks in mucus membrane
    2. Tooth Eruption
  • Symptoms
  1. Fever
  2. Fatigue
  3. Night Sweats
  4. Wasting
  5. Gastrointestinal upset
  1. Chronic unilateral, firm or fluctuant masses
  • Labs
  1. Alkaline Phosphatase increased
  2. Hemoglobin or Hematocrit consistent with Anemia
  3. Culture
    1. Blood Culture
    2. Bone Marrow Aspirate
    3. Lymph node biopsy
  4. Culture Sites not useful (may represent colonization)
    1. Sputum Culture
    2. Stool Culture
  5. Tuberculin Skin Testing
    1. Negative in 50% normal hosts (without Tuberculosis)
  • Prevention
  • Prophylaxis in HIV when CD4 Count < 50 cells/mm3
  1. Indicated for CD4 Cell Count < 50 cells/mm3 (previously <100 cells/mm3)
    1. If patients have delay in starting Antiretrovirals or optimized regimen cannot be used
  2. First-line prophylaxis
    1. Azithromycin 1200 mg PO each week
      1. More effective than Rifabutin and better tolerated with fewer Drug Interactions than Clarithromycin
  3. Other prophylaxis options
    1. Combination protocol
      1. Azithromycin weekly and
      2. Rifabutin daily
    2. Rifabutin 300 mg/day
      1. Reduces the Incidence of bacteremia by 50%
      2. Risk of Uveitis from rifabutin
    3. Clarithromycin 500 mg PO bid
      1. Azithromycin is better tolerated
      2. Decreases MAC infection by 68%
      3. Produces survival benefit
  • Management
  • MAC in HIV
  1. Colonization without bacteremia
    1. Should not be treated
    2. May be candidates for prophylaxis
  2. Treatment
    1. Clarithromycin and 1-2 other active agents
      1. Prevents resistance
    2. Continue drugs for the lifetime of the patient