Bacterium
Mycobacterium avium complex
Nontuberculous mycobacteria; disseminated in advanced HIV
my-koh-bak-TEER-ee-um AY-vee-um
High-yield clue
Disseminated MAC is a classic opportunistic infection of advanced HIV with CD4 counts under 50, presenting with fever, weight loss, and positive blood cultures.
Overview
A group of environmental nontuberculous mycobacteria (M. avium and M. intracellulare) that act as opportunistic pathogens. They are the classic teaching cause of disseminated infection in advanced HIV.
Classification
- Acid-fast bacilli
- Nontuberculous mycobacteria
- Slow-growing
- Environmental (water/soil)
- M. avium + M. intracellulare
Lab & identification clues
- Acid-fast staining
- Blood culture for disseminated disease
- Environmental water/soil source
- Slow-growing colonies
Associations
- Disseminated disease in advanced HIV (CD4 under 50)
- Pulmonary disease in older adults / chronic lung disease
- Cervical lymphadenitis in children
Commonly confused with
- Mycobacterium tuberculosis
- Mycobacterium leprae
Frequently asked questions
What is Mycobacterium avium complex?
A group of environmental nontuberculous mycobacteria (M. avium and M. intracellulare) that act as opportunistic pathogens. They are the classic teaching cause of disseminated infection in advanced HIV.
What are the lab clues for Mycobacterium avium complex?
Lab clues for Mycobacterium avium complex include Acid-fast staining, Blood culture for disseminated disease, Environmental water/soil source, and Slow-growing colonies.
What is Mycobacterium avium complex commonly confused with?
Mycobacterium avium complex is commonly confused with Mycobacterium tuberculosis and Mycobacterium leprae.
Original student-study summary. Sources checked: OpenStax Microbiology 2e, NCBI Bookshelf Medical Microbiology, and CDC topic pages where applicable; reviewed 2026-06. Educational only; no diagnosis, treatment, dosing, or specimen-handling guidance.