Mycobacterium Aviumcomplex (MAC)

This infection is caused by a group of bacteria called by one name Mycobacterium aviumcomplex (MAC). About half of the people with AIDS may develop MAC, especially when the CD4 cell count falls below 50.

Related to tuberculosis, MAC can affect the lungs or spread throughout the body. When it spreads, it usually gets into the gut, bone marrow, liver and spleen. People with advanced HIV infection and a CD4 cell count of less than 40 are more likely to have MAC throughout the body. MAC almost never causes disease in people with a CD4 count of more than 100.

The bacteria normally cause an infection of the lungs. But people with advanced HIV infection and a CD4 count less than 50 are more likely to develop an infection that can affect almost any internal organ.

Symptoms

Many of the signs of MAC are general. They include:

• Anemia (low red blood cells)
• Chills
• Diarrhea
• Fatigue
• High fevers
• Stomach aches
• Weight loss
• If MAC has spread, it can cause blood infections, hepatitis, pneumonia and other problems.

Causes

The bacteria that make up Mycobacterium aviumcomplex are common. They can be found in water, soil, dust and food. Almost everyone has them. A healthy immune system will control them. People with a weakened immune system may develop MAC disease.

Prevention

The bacteria that cause MAC can't be avoided. The best protection is a strong immune system. Antiretroviral therapy helps keep MAC in check.

The antibiotics azithromycin and clarithromycin help prevent MAC. These drugs are usually given to people who have a CD4 cell count of less than 75. Once CD4 cell counts go over 100 and stays there for three months, the antibiotics may be stopped, depending on the doctor's judgment.

Diagnosis

Many opportunistic infections cause symptoms like those of MAC. A doctor will take samples of blood, urine or saliva to check for the MAC bacteria. The sample will be used to grow bacteria to see what is there. This process, called culturing, can take several weeks. Even if a person is infected with MAC, it can be hard to find the MAC bacteria.

If a person has a CD4 cell count less than 50, the doctor may go ahead and treat him or her for MAC. This is because MAC infection is common but difficult to diagnose.

Treatment

 There isn't any cure for MAC. Treatment must continue for life to keep the infection from coming back. MAC bacteria can become resistant to some of the drugs used to fight it. Often, several antibiotics are used to treat MAC. At least two drugs are used, usually azithromycin or clarithromycin plus up to three other drugs.

People react differently to anti-MAC drugs. It may be necessary to try several combinations before one works with the fewest side effects. The most common MAC drugs are:

• Amikacin (Amkin), given as an injection. It may cause kidney and ear problems.
• Azithromycin (Zithromax), given as a shot or in capsules. It may cause nausea, headaches, vomiting or diarrhea.
• Ciprofloxacin (Cipro or Ciloxan), given as a shot or taken as tablets. It may cause nausea, vomiting or diarrhea.
• Clarithromycin (Biaxin): given as a shot or in capsules. It may cause nausea, headaches, vomiting or diarrhea.
• Ethambutol (Myambutol): It may cause nausea, vomiting or eye problems.
• Rifabutin (Mycobutin): It may cause rashes, nausea or anemia. It interacts badly with other drugs.
• Rifampin (Rifampicin, Rifadin, Rimactane): It may cause fever, chills, muscle or bone pain. This drug can turn urine, swea, and saliva red-orange. (It may stain contact lenses.) It interacts with other drugs, including anti-HIV drugs, antifungal drugs and birth control pills.

A person being treated for MAC needs to be sure that his or her doctor knows all the drugs that he or she is taking. This is vital to prevent drug interactions.

Cutting down on the amount of fat in the diet and eating more fruits and vegetables can help. As ongoing diarrhea can cause wasting, it is important to help build back any weight loss. These means eating healthy amounts of the right food. If loss of appetite is a problem, appetite-boosting drugs may be helpful. These include Marinol (gel-caps containing THC, the active ingredient in marijuana) and megestrol acetate (Megace).

Wasting causes a loss of muscle. Doing weightlifting or other exercises to build up muscles is helps the wasting.