What is Mycobacterium Avium Complex (MAC)

Mycobacterium avium complex is an infection caused by two similar and very common types of bacteria. MAC causes two types of infection:

• Local infection. This is limited to one area. If you have a normal disease-fighting system (immune system), you are more likely to get this type of infection.
• Disseminated infection. This is an infection that affects all parts of the body. It is more serious than a local infection. You are more likely to get this infection if you have a weak immune system.

MAC infections most often affect the lungs. MAC is not contagious. This means that it does not spread from person to person.

What are the causes?

This condition is caused by two kinds of bacteria, Mycobacterium avium and Mycobacterium intracellulare. These bacteria are often found in drinking water, hot tubs, swimming pools, house dust, and animals. You may become infected from:

• Breathing in water particles or dust particles that contain the bacteria (contaminated).
• Eating or drinking something that is contaminated.
• Drinking milk. MAC bacteria can grow in pasteurized milk.

What increases the risk?

The following factors may make you more likely to develop this condition:

• Having HIV or AIDS.
• Being a child.
• Being an older woman.
• Smoking cigarettes.
• Having long-term (chronic) lung diseases, such as:
  • Tuberculosis.
  • Chronic obstructive pulmonary disease (COPD).
  • Lung cancer.
  • Cystic fibrosis.

What are the signs or symptoms?

Symptoms vary depending on the type of MAC infection you have.

Symptoms of a local infection

• Lymph nodes that are bigger than usual (enlarged). Enlarged lymph nodes may be:
  • On one side of the neck.
  • Under the jaw.
  • Around the ear.
• Fatigue.
• Shortness of breath.
• A long-term cough that produces lots of mucus.
• Abnormal sounds when breathing. A health care provider may hear this when listening to your lungs.

Symptoms of a disseminated infection

• Fever.
• Night sweats.
• Weight loss.
• Loss of appetite.
• Fatigue.

How is this diagnosed?

This condition may be diagnosed based on:

• Your symptoms.
• A physical exam.
• Your medical history.

You may also have tests, including:

• Chest X-ray or CT scan.
• Blood tests.
• Test of mucus from your lungs (sputum) or other body fluids to see whether bacteria will grow (culture).
• Removal of a piece of body tissue to be checked under a microscope (biopsy).

How is this treated?

Treatment for this condition depends on the type of infection. Treatment may include:

• Taking antibiotic medicines. You may have to take antibiotics until MAC bacteria have stopped growing in cultures.
• Surgery to remove infected lymph nodes. After the lymph nodes are removed, antibiotics are usually not needed.

In some people with a disseminated infection, treatment with antibiotic medicines may continue for several years.

Follow these instructions at home:

Medicines

• Take over-the-counter and prescription medicines only as told by your health care provider.
• Take your antibiotic medicine as told by your health care provider. Do not stop taking the antibiotic even if you start to feel better.

Eating and drinking

• Eat a healthy, well-balanced diet. Talk with your health care provider or a diet and nutrition specialist (dietitian) about what food choices are best for you.
• Drink enough fluid to keep your urine pale yellow.

General instructions

• Seek medical care for any underlying health conditions you have. Follow your health care provider’s instructions about how to manage those conditions.
• Do not use any products that contain nicotine or tobacco, such as cigarettes and e-cigarettes. If you need help quitting, ask your health care provider.
• Keep all follow-up visits as told by your health care provider. This is important.

How is this prevented?

• Stay up-to-date on your vaccines.
• Take all of your medicines as told by your health care provider, especially if you have problems with your immune system.
• Avoid drinking water that may not be clean. Lakes, rivers, and other open water sources can contain germs that cause infections.
• Wash your hands often with soap and water. If soap and water are not available, use hand sanitizer.
• Practice safe food preparation, especially if your immune system is weak because of an underlying illness.
  • Store foods at safe temperatures.
  • Avoid eating raw or undercooked meats, poultry, fish, shellfish, and eggs.
  • Wash and peel fruits and vegetables before eating or cooking them.
  • Use separate food preparation surfaces and storage spaces for raw meat and for fruits and vegetables.
  • Wash your hands, food preparation surfaces, and utensils thoroughly before and after you handle raw foods.

Contact a health care provider if you:

• Have chills or a fever.
• Have a cough that does not go away.
• Have loss of appetite or weight loss.
• Feel very tired.

Get help right away if you:

• Have a fever for more than 2–3 days.
• Cough up blood.
• Have trouble breathing.
• Have chest pain.

Summary

• Mycobacterium avium complex (MAC) is an infection that is caused by two similar and very common types of bacteria.
• If you have a normal disease-fighting system (immune system), you are more likely to get an infection that is limited to one area of your body (local infection).
• If you have a weak immune system, you are likely to get infections in all parts of your body (disseminated infection).
• Treatment for this condition is difficult because MAC does not respond to many common antibiotic medicines. Treatment depends on the type of infection, and may involve surgery or antibiotics.