Mycobacterial Infections, Atypical
Atypical mycobacterial (my-ko-bak-TEER-e-ul) infections are infections caused by mycobacteria * other than those that cause tuberculosis *
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Mycobacteria other than tuberculosis (MOTT)
Mycobacterium avium complex (MAC)
What Are Atypical Mycobacterial Infections?
Atypical mycobacteria are commonly found in the environment, like in soil and water, and in food. Most of the time they do not cause infection or illness in healthy people. When a person's immune system is weakened, however, as in people who have HIV or AIDS, several strains of mycobacteria can cause opportunistic infections * . Atypical mycobacteria are related to the bacterium that causes tuberculosis (TB), but they often are resistant to the drugs used to treat TB. These strains are called mycobacteria other than tuberculosis, or MOTT.
Although some mycobacteria can live on human skin or in the nose, atypical mycobacterial infections are not known to spread from person to person. Rather, infection comes from direct contact with the bacteria in the environment.
Are Atypical Mycobacterial Infections Common?
Mycobacterial infections other than tuberculosis are uncommon, and they most frequently affect people with HIV or AIDS. As cases of HIV and AIDS have increased, so have cases of mycobacterium infections. In the United States, these infections are more common than tuberculosis. People with seriously weakened immune systems or chronic lung disease are at greatest risk.
* mycobacteria (my-ko-bak-TEER-e-uh) belong to a family of bacteria called "fungus bacteria' because they are found in wet environments.
* tuberculosis (too-ber-kyoo-LO-sis) is a bacterial infection that primarily attacks the lungs but can spread to other parts of the body.
* opportunistic infections are infections caused by infectious agents that usually do not produce disease in people with healthy immune systems but can cause widespread illness in patients with weak or faulty immune systems.
How Do People Know They Have an Atypical Mycobacterial Infection?
Signs and symptoms of atypical mycobacterial infections include fever, swollen lymph nodes, extreme tiredness, night sweats, weight loss, diarrhea (dye-uh-REE-uh), joint and bone pain, cough, shortness of breath, skin lesions * , general discomfort, and paleness. Many of these symptoms can be signs of less serious conditions, but in a person with a weakened immune system a combination of such symptoms suggests a MOT T infection. In children, lymphadenitis * is the most common type of MOT T infection, whereas lung infections, which occur less often in children, are the most common in adults.
What Are Some Specific Infections?
Mycobacterium avium complex (MAC)
MAC includes the species Mycobacterium avium (A-vee-um) and Mycobacterium intracellulare (in-truh-sel-yoo-LAR-e) and most commonly causes lymphadenitis and lung disease in otherwise healthy people. Patients who have AIDS are particularly susceptible to MAC, and it often spreads to the blood, lungs, spleen, liver, bone marrow * , and intestines in people with HIV. MAC infection in an HIV-positive person can signal the start of full-blown AIDS. Disseminated disease * rarely occurs in people with healthy immune systems.
This infection causes skin lesions, sometimes known as swimming pool granuloma * or fish tank granuloma. Infection with M. marinum (MAR-ih-num) is very rare, occurring in less than 1 in 100,000 people. Those who are most at risk include people with weakened immune systems and people who handle fish, are exposed to contaminated water in aquariums, or swim in fresh or salt water that contains the mycobacterium. Several weeks after a person has contact with contaminated water, a bump appears on a hand, arm, or foot where there was a break in the skin. The lesion grows and drains over several weeks, leaving an ulcer * . Occasionally, a deep infection will cause tenderness and swelling in the nearby bone or joints.
Mycobacterium ulcerans (UL-sir-ans) is found in tropical and subtropical regions in Asia, the Western Pacific, and Latin America, although it is most common in West Africa. The infection causes skin lesions known as Buruli (boo-REH-lee) ulcers, named for a region in Uganda in Africa. The ulcers develop mainly on the limbs, grow slowly, and release a toxin (or poison) that damages the skin and underlying tissue. The infection is relatively painless, but if left untreated it can destroy massive amounts of skin and bone, leading to permanent deformities.
* lesions (LEE-zhuns) is a general term referring to a sore or a damaged or irregular area of tissue.
* lymphadenitis (lim-fah-den-EYE-tis) is inflammation of the lymph nodes and channels of the lymphatic system.
* bone marrow is the soft tissue inside bones where blood cells are made.
* disseminated disease describes a disease that has spread widely in the body.
* granuloma (gran-yoo-LO-muh) is chronically inflamed and swollen tissue that often develops as the result of an infection.
* ulcer is an open sore on the skin or the lining of a hollow body organ, such as the stomach or intestine. It may or may not be painful.
Infection with Mycobacterium kansasii (kan-ZAS-e-eye) causes a lung disease similar to tuberculosis, although not as severe. Patients may experience fever and cough, and a doctor often hears wheezing and "crackling" when listening to the patient's lungs. It also can involve the lymph nodes and cause skin lesions. In people with weak immune systems, the infection can erupt into widespread disease. This infection is rare in the United States, but people with chronic lung disease are especially susceptible. If left untreated, the disease frequently worsens and can be fatal.
How Do Doctors Diagnose and Treat Atypical Mycobacterial Infections?
A doctor can perform several tests to detect mycobacteria, including examination and culture * of samples of blood, sputum * , bowel movement, or bone marrow. Chest X rays or computerized tomography * (CT) scans can show disease in the lungs. Some cases may require endoscopy * to collect a sample of lung or stomach tissue or biopsies * of skin or lymph node tissue. Quickly diagnosing mycobacterial infections is crucial, as treatment needs to begin as soon as possible.
The PPD (purified protein derivative) skin test for tuberculosis will often be positive, although not as strongly so, in people who have an atypical mycobacterial infection, because atypical mycobacteria are so similar to the bacterium that causes TB.
Treatment for mycobacterial infections depends on the type of bacterium, the location and severity of the infection, and the status of the person's immune system. Resistant and severe infections usually need to be treated with a combination of antibiotics, and up to six medications may be used at once. Surgery, sometimes along with medications, is the most effective way to treat lymph node infections and skin lesions.
Treatment for MOTT infections can take as long as 6 months to 2 years. Antibiotics work during the growth stage of bacteria, and mycobacteria are slow growing. If left untreated, MOTT infections can spread throughout the body, especially in people with weak immune systems. They can cause abscesses * , bone and joint infections, and infections of the lymph nodes, lungs, or soft tissue. Widespread infections can lead to serious illness and even death.
Can People Prevent Atypical Mycobacterial Infections?
Because mycobacteria are common in the environment, these infections are difficult to prevent, especially in people with weakened immune systems. Preventive medications are prescribed for people at risk, such as those with HIV or AIDS. Getting enough sleep and eating a healthy diet also can help these patients cope with and fight these infections.
* culture (KUL-chur) is a test in which a sample of fluid or tissue from the body is placed in a dish containing material that supports the growth of certain organisms. Within days or weeks the organisms will grow and can be identified.
* sputum (SPYOO-tum) is a substance that contains mucus and other matter coughed out from the lungs, bronchi, and trachea.
* computerized tomography (kom-PYOO-ter-ized toe-MAH-gruh-fee) or CT, also called computerized axial tomography (CAT), is a technique in which a machine takes many X rays of the body to create a three-dimensional picture. *
* endoscopy (en-DOS-ko-pee) is a type of diagnostic test in which a lighted tube-like instrument is inserted into a part of the body.
* biopsies (BI-op-seez) are tests in which small samples of skin or other body tissue are removed and examined for signs of disease.
* abscesses (AB-seh-sez) are localized or walled off accumulations of pus caused by infection that can occur anywhere in the body.
U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton Road, Atlanta, GA 30333. The CDC is the U.S. government authority for information about infectious and other diseases. It provides information about Mycobacterium avium complex at its website. Telephone 800-311-3435 http://www.cdc.gov
U.S. National Library of Medicine, 8600 Rockville Pike, Bethesda, MD 20894. The National Library of Medicine has a website packed with information on diseases (including atypical mycobacterial infections) and drugs, consumer resources, dictionaries and encyclopedias of medical terms, and directories of doctors and helpful organizations. Telephone 888-346-3656 http://www.nlm.nih.gov