Tuberculosis (TB)

Tuberculosis is a leading cause of death among people living with AIDS. HIV infection and tuberculosis are a threatening pair. Each makes the other worse. People with HIV have a 100 times greater risk of developing active TB and becoming infectious than people who donÕt have TB.

Having HIV makes it more likely that a person will get tuberculosis. In addition, it makes it more likely that the tuberculosis will go from a sleeping infection to an active one. Furthermore, tuberculosis makes the AIDS virus copy itself faster. TB often shows up in a person with HIV years before other problems linked to HIV appear. Suddenly getting TB Ð especially in a site outside the lungs Ð often is one of the first indications of HIV infection.

Tuberculosis is caused by bacteria. The name comes from the word tubercles. These are small hard lumps created when the immune system builds a wall around the TB bacteria in the lungs.

Symptoms

Signs of active TB infection are like those of Pneumocystis pneumonia. They include:

• Coughing for more than three weeks. The cough appears at first with yellow or green mucus. Later, bloody mucus may appear.
• Feeling tired
• Night sweats
• Not feeling well
• Pain in the chest, back or kidneys Ð or all three
• Shortness of breath
• Slight fever
• Weight loss

Active TB can occur at any CD4 level.

Causes

TB is an infection caused by mycobacterium tuberculosis. The bacteria spread from one person to another through the air. This usually happens when someone with TB sneezes or coughs. In that way, TB is quite contagious. But in normal daily life, simply passing an infected person isn't likely to spread the infection.

The bacteria can live in an inactive form in the body. Most people who have bee exposed never have signs of the infection. TB infection is usually found in the lungs, but it can spread throughout the body. People with HIV who have a CD4 count of less than 200 are at a greater risk of having the TB spread to organs besides the lungs.

When the immune system gets weak, the bacteria can become active. Once this happens, the bacteria kill tissues in the infected organs. This can sometimes cause death.

Prevention

Soon after a person is diagnosed as being HIV-positive, he or she should have a test for TB. The Mantoux skin test is the most reliable way of telling if a person has the infection. It involves injecting a small amount of liquid under the top layer of skin on the arm. After two to three days, a doctor or nurse will check the spot. If there is a hard, red welt where the injection was done, the person has been infected with TB at some point. A chest X-ray should be done to make sure the infection is not active. If itÕs not, steps should be taken to prevent it from becoming active in the future.

Diagnosis

When tuberculosis is inactive, a person usually doesnÕt have symptoms. The Mantoux test is the best way to learn whether a person has TB. A positive test means that the person has been exposed to TB. It doesnÕt mean that the TB infection is active. A doctor may do chest X-rays, ask about other symptoms or do a sputum culture. This involves getting samples of sputum from the lungs and airways leading from them. The sample is then used to try to grow TB bacteria. This can take four weeks.

Sometimes, if there has been enough damage to the immune system, the body wonÕt react to the test even when the person has TB infection. (This is called anergy.) In that case, the best way to test for TB infection is a sputum culture.

Treatment

If a person with HIV is infected with TB, treatment will be needed to keep it from becoming active. This will help keep it spreading to other people. It will also help keep it spreading throughout the body. TB that resists drugs is a concern to people with HIV/AIDS because it makes treatment harder.

A person infected with inactive is usually given an antibiotic (isoniazid Ð INH) for at least six months or INH plus one or two other drugs for three months. Using more than one drug is more effective than just using INH. It is important to take all the drugs for as long as they have been prescribed. If a person doesnÕt, the TB infection might become resistant and the anti-TB drugs will stop working.

Some antibiotics used to treat TB can damage the liver or kidneys. Antiretroviral therapy can do the same thing. It may be hard to take drugs for both TB and HIV at the same time. INH can cause liver problems especially for black or Hispanic women. It can also cause peripheral neuropathy.

If a person is considering starting antiretroviral therapy but has TB, the TB should be treated first. (This may not be possible if CD4 cell counts are too low.) Two drugs used to fight TB Ð rifampin or rifabutin Ð can cause antiretroviral drugs in the blood to drop so low they donÕt work against HIV. On the other hand, antiretroviral drugs can raise the levels of rifampin or rifabutin so high that there are serious side effects. Rifampin should not be used with most protease inhibitors. Special guidelines for doctors treating people for TB and HIV at the same time are available from the Centers for Disease Control.