Mycobacterium Avium Complex infections

What causes mycobacterium avium complex infections?

Mycobacterium avium complex (MAC) infections are caused by two types of bacteria: Mycobacterium avium and Mycobacterium intracellulare. These bacteria are found in many places including water (fresh or salt), household dust, and soil. MAC bacteria get into the body when the bacteria are inhaled into the lungs or swallowed. Most people have MAC bacteria in their bodies and never get sick. MAC bacteria primarily cause illness in people who have poorly working immune systems or lung disease. Touching the same objects or having a close relationship with people who are sick from a MAC infection does not seem to increase the chance of getting sick. MAC infections are not thought to be contagious from one person to another.

Last updated on 05-01-20

How are mycobacterium avium complex infections diagnosed?

Diagnosis of a pulmonary mycobacterium avium complex (MAC) infection is based on a combination of physical exam findings, laboratory test results, and lung x-rays or CT scan results. The laboratory tests include cultures of mucus spit up from the lungs (sputum) and special staining (acid-fast bacillus test). A laboratory culture involves placing cells from a sputum sample in an environment that encourages the bacteria to grow. Results identifying the bacteria may take several days or longer. Because the symptoms of MAC infections are similar to those of other types of infections, other types of infections and diseases must also be ruled out.

Diagnosis of disseminated MAC infection is suspected based on symptoms and is confirmed in cultures of blood and often lymph node cells. Cultures of cells from urine, stool, liver or bone marrow may also be helpful. CT scans may be used to try to determine the different sites of infection in the body. If pulmonary or disseminated MAC infection is suspected, an HIV test may be done, as well as other tests, to rule out other associated medical conditions.

A diagnosis of MAC lymphadenitis is confirmed by finding the bacteria in the culture of lymph node cells. These cells are collected by a biopsy of a swollen lymph node.

Last updated on 05-01-20

Is Mycobacterium avium complex infection inherited?

Mycobacterium avium complex (MAC) infection is caused by bacteria and is not an inherited condition. To become infected with MAC bacteria and get sick, a person must first be exposed to one of the associated types of bacteria.

There have been a few reports of families with more than one family member with a MAC infection. In these families, it is thought that there is a variation in a gene or genes involved with the body's immune response. A genetic variant in an immune system gene may make some people more likely to get sick from an infection than others. There are many genes involved in the human immune response, and there is no single gene known to be responsible for MAC infections.

Last updated on 05-01-20

What is the long-term outlook for people with mycobacterium avium complex infections?

The long-term outlook (prognosis) for people who are sick from mycobacterium avium complex (MAC) infections depends on the type of infection and whether or not the person has other medical conditions or health problems. One published study reviewed the long-term outlook of people with MAC infections with and without other diseases, and found a 75% chance for survival five years after their first diagnosis.

People who are HIV-positive with MAC infections may have a shortened lifespan depending on their immune systems and their response to HIV medications. For people who have had successful treatment, there is still a chance that the infection will come back, so people who have been sick from a MAC infection need to be monitored over time.

In HIV-negative people with lung disease from a MAC infection, the treatment success rates range from 20-90% in different studies. People with certain types of lung disease, people who are underweight, and people with anemia are more likely to have a poor outcome than other HIV-negative people affected by a MAC infection.

MAC lymphadenitis in children generally does not impact their health. In some cases, the condition may go away even without treatment.

Last updated on 05-01-20

How might mycobacterium avium complex infections be treated?

Mycobacterium avium complex (MAC) infection is classified into several different types including:

  • Pulmonary MAC infection, which affects the lungs
  • Disseminated MAC infection, which affects many different parts of the body
  • MAC lymphadenitis, which causes swollen lymph nodes

Treatment options for MAC infections vary by type of infection and by the presence of other medical conditions such as AIDS, cystic fibrosis, COPD, or cancer.

Pulmonary MAC infections and disseminated MAC infections are usually treated with a combination of antibiotic medications. There are many types of antibiotics approved for treating MAC infections A combination of medicines is used because some of the disease-causing bacteria can be resistant to certain types of antibiotics. Using more than one antibiotic reduces the chance for the MAC bacteria to come back after treatment is over.

For people who have both HIV/AIDS and a MAC infection, treatment usually involves a combination of different antibiotics for the MAC infection and antiretroviral therapy to treat the HIV infection.

In special circumstances, there is some evidence to suggest that surgery to remove a single spot of infection in one lung can be helpful in people who have had a poor response to drug therapy. Surgery is usually only done when the infection is found in only one lung and the surgery won't cause any long- term harm.

Treatment of MAC lymphadenitis usually involves surgical removal of affected lymph nodes. Antibiotics may also be prescribed depending on the severity of infection and the response to surgery.

Last updated on 05-01-20

In-Depth Information

The AIDS Education and Training Center (AETC)

The AIDS Education and Training Center (AETC) offers information on Mycobacterium Avium Complex infections. Click on the link to view this information page.

Last updated on 04-27-20

Name: NTM Info & Research supports pulmonary NTM infections 550 Madruga Avenue, Suite 230
Coral Gables, FL, 33146,
Phone: 305-667-6461, ext 26 and 32 Email: Url:
Diel R, Lipman M, Hoefsloot W. High mortality in patients with Mycobacterium avium complex lung disease: a systematic review BMC Infect Dis. 2018; 18(206). 1-10. Reference Link

Note, these links are external searches against the National Laboratory of Medicine's drug database. You may need to adjust the search if there are no results found.

Drug Name Generic Name
Arikayce liposomal amikacin

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