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Mycobacterium Avium ComplexAka: Mycobacterium Avium Intracellulare

Epidemiology
1. Disseminated MAC infection: 40% of North American AIDS
2. Most common reported HIV bacterial infection
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
Signs: Normal Children with Lymphadenitis
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 < 100
1. Indicated for CD4 Cell Count < 100
2. Combination protocol recommended
  1. Azithromycin weekly and
  2. Rifabutin daily
3. Rifabutin 300 mg/day
  1. Reduces the Incidence of bacteremia by 50%
  2. Risk of Uveitis from rifabutin
4. Azithromycin 1200 mg PO each week
  1. More effective than Rifabutin
5. Clarithromycin 500 mg PO bid
  1. Decreases MAC infection by 68%
  2. 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
References
1. Weller (2001) BMJ 322:1350

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This page was written by Scott Moses, MD. This page was last revised before 5/10/08, prior to consistent tracking of revision date. This page was last published on 5/10/2008. Please send comments and questions to the editor. Contact information may be found on the page About the Family Practice Notebook. These pages are best viewed with Microsoft Internet Explorer 6.0.