Mycobacterium Avium Complex

Date: March 1, 1997
Source: National Institutes of Health (NIH)
Author: National Institute of Allergy and Infectious Diseases (NIAID)

Mycobacterium avium complex, also known as MAC, is a bacterial infection that can be localized (limited to a specific organ or area of the body) or disseminated throughout the body. It is a life-threatening disease, although new treatments offer promise for both prevention and treatment. MAC disease is extremely rare in people who are not infected with HIV, the virus that causes AIDS.

Symptoms and Diagnosis

Disseminated MAC can affect almost any organ of the body. It can cause symptoms of fever, weight loss, night sweats, fatigue, loss of appetite, loose stools or diarrhea, abdominal pain, anemia (low numbers of red blood cells) and enlargement of the liver or spleen.

The symptoms of MAC resemble those of many other conditions in people with AIDS. The diagnosis of MAC is made by identifying the organism in blood samples or tissue from affected organs such as bone marrow or liver tissue.


Acute. Doctors use a number of different drug combinations to treat MAC. Multiple drugs are required to treat these infections because the organisms may become resistant to just one drug. A 1993 task force of the U.S. Public Health Service (USPHS) recommended that at least two drugs be used, one of which should be either azithromycin or clarithromycin. Doctors frequently add one or more of the following as second, third, or fourth agents: ethambutol, rifabutin, rifampin, ciprofloxacin, and in some situations amikacin. Treatment should continue for life to prevent recurrence of the disease.

Preventive Therapy. A 1994 USPHS task force on preventive therapy recommends that people with HIV and CD4+ T-cell counts of less than 75 may benefit from treatment to prevent an initial episode of MAC. (CD4+ T cells are the crucial immune cells targeted by HIV.) Before beginning preventive therapy, people with HIV should be tested to be sure that they do not have active MAC or tuberculosis (TB). Tests for TB may include an x-ray, tuberculin skin tests, and a blood test.

The first-line therapy for MAC prevention is either azithromycin or clarithromycin. Rifabutin, which is also approved for MAC prevention, should not be used if a person is also taking protease inhibitors, drugs used to treat HIV disease.


The National Institute of Allergy and Infectious Diseases (NIAID) funds research aimed at finding therapies for treating and preventing MAC disease.

For information about clinical studies, call the AIDS Clinical Trials Information Service: 1-800-TRIALS-A (1-800-874-2572) 1-800-243-7012 (Deaf Access/TDD)

For information on federally approved treatment guidelines and information, call the HIV/AIDS Treatment Information Service: 1-800-HIV-0440 (1-800-448-0440) 1-800-243-7012 (Deaf Access/TDD)

NIAID, a component of the National Institutes of Health supports research on AIDS, tuberculosis and other infectious diseases as well as allergies and immunology. NIH is an agency of the U.S. Public Health Service, U.S. Department of Health and Human Services.

Prepared by:
Office of Communications, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
Public Health Service, U.S. Department of Health and Human Services
March 1997