Mycobacterium avium-intracellulare

Last reviewed 01/2018

Mycobacterium avium intracellulare (MAI) is an opportunistic human pathogen.

  • Mycobacterium avium-intracellulare (MAI) is a common opportunistic infection (OI) associated with acquired immune deficiency syndrome (AIDS) patients
    • the organism is generally ubiquitous in soil and in the environment, but it is readily cleared in most human hosts (1)
    • in AIDS - generally, prophylaxis consists of a once-weekly macrolide in patients with a CD4 cell count less than 75 (2)

MAI is an important, if unusual, cause of pulmonary disease in patients with pre-existing lung damage.

In cases of profound immune suppression, for example in the terminal phase of AIDS, MAI causes a disseminated infection.

Clinical diagnosis is often difficult in patients who are already severely unwell. Characteristic features include fever and diarrhoea. It appears that the organism causes relatively little tissue damage.

MAI causes diarrhoea in up to 10% of HIV infected patients with CD4 counts less than 150/ml. Positive stool cultures may only indicate colonization with MAI, so jejunal biopsy may be required to determine if MAI is of pathogenic importance.


  • Kasperbauer SH, Daley CL. Diagnosis and treatment of infections due to Mycobacterium avium complex. Semin Respir Crit Care Med. 2008;29(5):569-576
  • Powderly WG. Prophylaxis for opportunistic infections in an era of effective antiretroviral therapy. Clin Infect Dis. 2000;31(2):597-601.