AIDS InfoNet Logo
This website is certified by Health On the Net Foundation. Click to verify.
This site complies with the HONcode standard for trustworthy health information:
verify here.

The Henry J. Kaiser Family Foundation
Site of the Week
November 2003

The Health Leader Award 2006
The Health Leader Award 2006

The HOPE Reward Medical Award Featured Site Award

IBS Tales Hope Award Editor's Choice Award

Listed in Listed in Treasures of the Internet

AIDS InfoNet Logo.  The AIDS InfoNet - Reliable, Up-to-Date AIDS Treatment Information
International Association of Providers of AIDS Care
Reviewed September 30, 2014

Fact Sheet 514

Mycobacterium Avium Complex (MAC)



Mycobacterium Avium Complex (MAC) is a serious illness caused by common bacteria. MAC is also known as MAI (Mycobacterium Avium Intracellulare). MAC infection can be localized (limited to one part of your body) or disseminated (spread through your whole body, sometimes called DMAC). MAC infection often occurs in the lungs, intestines, bone marrow, liver, and spleen.

The bacteria that cause MAC are very common. They are found in water, soil, dust, and food. Almost everyone has them in their body. A healthy immune system will control MAC, but people with weakened immune systems can develop MAC disease.

Up to 50% of people with AIDS may develop MAC, especially if their CD4 cell count is below 50. MAC almost never causes disease in people with more than 100 CD4 cells.



The symptoms of MAC can include high fevers, chills, diarrhea, weight loss, stomach aches, fatigue, and anemia (low numbers of red blood cells). When MAC spreads in the body, it can cause blood infections, hepatitis, pneumonia, and other serious problems.

Many different opportunistic infections can cause these symptoms. Therefore, your health care provider will probably check your blood, urine, or saliva to look for the bacteria that causes MAC. The sample will be tested to see what bacteria are growing in it. This process, called culturing, can take several weeks. Even if you are infected with MAC, it can be hard to find the MAC bacteria.

 If your CD4 cell count is less than 50, your health care provider might treat you for MAC, even without a definite diagnosis. This is because MAC infection is very common but can be difficult to diagnose.



The MAC bacteria can mutate and develop resistance to some of the drugs used to fight it. Health care providers use a combination of antibacterial drugs (antibiotics) to treat MAC. At least two drugs are used: usually azithromycin or clarithromycin plus up to three other drugs. MAC treatment must continue for life, or else the disease will return.

People react differently to anti-MAC drugs. You and your health care provider may have to try different combinations before you find one that works for you with the fewest side effects.

 The most common MAC drugs and their side effects are:

  • Amikacin (Amkin): kidney and ear problems; taken as an injection.
  • Azithromycin (Zithromax, see fact sheet 530): nausea, headaches, vomiting, diarrhea; taken as capsules or intravenously.
  • Ciprofloxacin (Cipro or Ciloxan, see fact sheet 531): nausea, vomiting, diarrhea; taken as tablets or intravenously.
  • Clarithromycin (Biaxin, see fact sheet 532): nausea, headaches, vomiting, diarrhea; taken as capsules or intravenously. Note: The maximum dose is 500 milligrams twice a day.
  • Ethambutol (Myambutol): nausea, vomiting, vision problems.
  • Rifabutin (Mycobutin): rashes, nausea, anemia. Many drug interactions.
  • Rifampin (Rifampicin, Rifadin, Rimactane): fever, chills, muscle or bone pain; can turn urine, sweat, and saliva red-orange (may stain contact lenses); can interfere with birth control pills. Many drug interactions.



The bacteria that cause MAC are very common. It is not possible to avoid being exposed. The best way to prevent MAC is to take strong antiretroviral medications (ARVs). Even if your CD4 cell count drops very low, there are drugs that can stop MAC disease from developing in up to 50% of people.

The antibiotic drugs azithromycin, rifabutin, and clarithromycin have been used to prevent MAC. These drugs are usually prescribed for people with less than 50 CD4 cells.

Combination antiretroviral therapy can make your CD4 cell count go up. If it goes over 100 and stays there for 3 months, it may be safe to stop taking medications to prevent MAC. Be sure to talk with your health care provider before you stop taking any of your prescribed medications.




Several drugs used to treat MAC interact with many other drugs, including ARVs, antifungal drugs, and birth control pills. This is especially true for rifampin, rifabutin, and rifapentine. Be sure your health care provider knows about all the medications that you are taking so that all possible interactions can be considered.




MAC is a serious disease caused by common bacteria. MAC can cause serious weight loss, diarrhea, and other symptoms.

If you develop MAC, you will probably be treated with azithromycin or clarithromycin plus one to three other antibiotics. You will have to continue taking these drugs for life to avoid a recurrence of MAC.

People with 50 CD4 cells or less should talk with their health care providers about taking drugs to prevent MAC.



Back to Fact Sheet Categories

International Association of Providers of AIDS Care


The AIDS InfoNet is a project of the International Association of Providers of AIDS Care.


United States National Library of Medicine

Partially funded by the National Library of Medicine

Search Our Site
Newest Fact Sheets
Print This Fact Sheet
You can print this fact sheet on a single page in Microsoft Word (.doc) format or Adobe Acrobat (.pdf) format. Click on the links below to open the document in your browser and then print it.
 Adobe Acrobat PDF
 Microsoft Word

You can print directly from your browser using the link below. The printout will probably go onto a second page.
 Print Version (Web)

Monthly E-mail Updates

The InfoNet updates its Fact Sheets frequently. A listing of each month's changes is posted to several e-mail lists.

If you would like to receive this monthly update by personal e-mail, please click on the SUBMIT button.