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Mycobacterial Infections, Atypical

Mycobacterial Infections, Atypical

Definition

Atypical mycobacterial infections are infections caused by several types of mycobacteria similar to the germ that causes tuberculosis. These atypical mycobacterial infections are a frequent complication in patients with human immunodeficiency virus (HIV) infection or AIDS.

Description

Mycobacteria are a group of rod-shaped bacteria that cause several diseases, among them leprosy and tuberculosis. For some time, scientists have known of bacteria that are similar to Mycobacterium tuberculosis, the cause of tuberculosis, but that grow and act differently. When tuberculosis was a much more widespread problem and microbiology was much less able to tell the difference between similar microbes, these atypical mycobacteria were ignored. Today, they have been classified more precisely as members of the same species and called atypical (or nontuberculosis) mycobacteria.

Although the medical profession has known about these atypical infections for a long time, they were not considered a serious problem until the early 1980s. It was then that many of these atypical infections were noticed among homosexuals and intravenous drug users in New York City. These bacteria rarely cause infection in humans other than those with HIV or AIDS.

Causes and symptoms

Although there are more than a dozen species of atypical mycobacteria, the two most common are Mycobacterium kansasii and M. avium-intracellulare. These microbes are found in many places in the environment: tap water, fresh and ocean water, milk, bird droppings, soil, and house dust. The manner in which these bacteria are transmitted is not completely understood. There is no evidence that they are transmitted from person to person.

M. avium-intracellulare (MAC or MAI) is a rare cause of lung disease in otherwise healthy humans but a frequent cause of infection among those whose resistance has been lowered by another disorder (opportunistic infection). According to some experts, MAC infection is an almost inevitable complication of HIV. The infection is caused by one of two similar organisms, M. avium and M. intracellulare.

AIDS patients are almost always attacked by these mycobacteria. Once inside the body, the atypical mycobacterial organisms colonize and grow in the lungs like tuberculosis. Because AIDS patients have a poorly functioning immune system, the microbes multiply because they aren't stopped by the body's normal response to infection. Once they have colonized the lungs, the organisms enter the bloodstream and spread throughout the body, affecting almost every organ. These devastating infections can invade the lymph nodes, liver, spleen, bone marrow, gastrointestinal tract, skin, and brain.

Symptoms include shortness of breath, fever, night sweats, weight loss, appetite loss, fatigue, and progressively severe diarrhea, stomach pain, nausea and vomiting. If the infection spreads to the brain, the patient may experience weakness, headaches, vision problems, and loss of balance.

MAC and M. kansasii sometimes cause lung infections in middle-aged and elderly people with chronic lung conditions. MAC, M. kansasii, and M. scrofulaceum may cause inflammation of the lymph nodes in otherwise healthy young children. M. fortuitum and M. chelonae cause skin and wound infections and abscesses after trauma or surgical procedures. M. marinum causes a nodular inflammation, usually on the arms and legs. This infection is called "swimming pool granuloma" because it is associated with swimming pools, fish tanks, and other bodies of water. M. ulcerans infection causes chronic skin ulcerations, usually on an arm or leg. Atypical mycobacteria infections can also occur without causing any symptoms. In such cases, a tuberculin skin test may be positive.

Diagnosis

The diagnosis is made from the patient's symptoms and organisms grown in culture from the site of infection. In cases of lung infection, a diagnostic workup will include a chest x ray and tests on discharges from the respiratory passages (sputum).

Treatment

These nontypical mycobacteria are not easy to treat in any patient and the problem is complicated when the person has AIDS. Antibiotics are not particularly effective, although rifabutin (a cousin of the anti-tuberculosis drug rifampin) and clofazimine (an anti-leprosy drug) have helped some patients. It is also possible to contain the infection to some degree by combining different drugs, including ethionamide, cycloserine, ethambutol, and streptomycin.

Prognosis

Because drug therapy is not easily effective, the overwhelming infections caused by these mycobacteria in AIDS patients can be fatal.

Prevention

People with HIV infection can prevent or delay the onset of MAC by taking disease-preventing drugs such as rifabutin.

AIDS patients and persons with tissue damage, such as skin wounds or pulmonary disease, can make a number of lifestyle changes to help prevent MAC infection. Since these mycobacteria are found in most city water systems, in hospital water supplies, and in bottled water, at-risk persons should boil drinking water. Persons at risk should also avoid raw foods, especially salads, root vegetables, and unpasteurized milk or cheese. Fruits and vegetables should be peeled and rinsed thoroughly. Conventional cooking (baking, boiling or steaming) destroys mycobacteria, which are killed at 176°F (80°C).

KEY TERMS

Culture A test in which a sample of body fluid, such as prostatic fluid, is placed on materials specially formulated to grow microorganisms. A culture is used to learn what type of bacterium is causing infection.

Human immunodeficiency virus (HIV) The virus that causes AIDS.

Finally, at-risk patients should avoid contact with animals, especially birds and bird droppings. Pigeons in particular can transmit MAC.

Resources

ORGANIZATIONS

National AIDS Treatment Advocacy Project. 580 Broadway, Ste. 403, New York, NY 10012. (888) 266-2827. http://www.natap.org.

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Mycobacterial Infections, Atypical

Mycobacterial infections, atypical

Atypical mycobacteria are species of mycobacteria that are similar to the mycobacteria that are the cause of tuberculosis . Like other mycobacteria, they are rod-like in shape and they are stained for observation by light microscopy using a specialized staining method called acid-fast staining. The need for this staining method reflects the unusual cell wall chemistry of mycobacteria, relative to other bacteria . In contrast to other mycobacteria, atypical mycobacteria do not cause tuberculosis. Accordingly, the group of bacteria is also described as nonpneumoniae mycobacteria. This group of bacteria is also designated as MOTT (mycobacteria other than tuberculosis). Examples of atypical mycobacteria include Mycobacterium kansasii, Mycobacterium avium, Mycobacterium intracellulare, Mycobacterium marinum, and Mycobacterium ulcerans.

The atypical mycobacteria are widely present in the environment. They inhabit fresh and salt water, milk, soil, and the feces of birds. Other environmental niches, which so far have not been determined, are possible. The nature of their habitats suggests that transmission to people via soiled or dirty hands, and the ingestion of contaminated water or milk would be typical. Yet, little is still known about how people become contaminated. One species, known as Mycobacterium marinum, is found in swimming pool water, and can cause a skin infection in fingers or toes upon contact with the skin of a swimmer. Additionally, some evidence supports the transmission of atypical mycobacteria in aerosols (that is, as part of tiny droplets that can drift through the air and become inhaled).

Contamination with atypical mycobacteria may be a natural part of life. For the majority of people, whose immune systems are functioning efficiently, the microbe does not establish an infection. However, for those who immune system is not operating well, the presence of the atypical mycobacteria is a problem. Indeed, for those afflicted with acquired immunodeficiency syndrome (AIDS ), infection with atypical mycobacteria (typically with Mycobacterium avium and Mycobacterium intracellulare ) is almost universal.

Atypical mycobacteria tend to first establish a foothold in the lungs. From there the bacteria can spread, via the bloodstream, throughout the body. Infections in almost every organ of the body can ensue. Examples of sites of infection include the brain, lymph nodes, spleen, liver, bone marrow, and gastrointestinal tract. The overwhelming nature of the infections can be fatal, especially to people already weakened by AIDS.

The spectrum of infection sites produces a wide range of symptoms, which include a feeling of malaise, nausea, worsening diarrhea, and, if the brain is affected, headaches, blurred vision, and loss of balance.

Infrequently, those with healthy immune systems can acquire an atypical mycobacterial infection. The result can be a bone infection (osteomyelitis), a form of arthritis known as septic arthritis, and localized infections known as abscesses.

The diagnosis of infection caused by atypical mycobacteria is complicated by the fact that the growth of the microorganisms on conventional laboratory agar is very difficult. Specialized growth medium is required, which may not be available or in stock in every clinical laboratory. The delay in diagnosis can result in the explosive development of multi-organ infections that are extremely difficult to treat.

Treatment of atypical mycobacteria is complicated by the unusual cell wall possessed by the bacterium, relative to other bacteria. The cell wall is made predominantly of lipids. Partially as a result of their wall construction, atypical mycobacteria are not particularly susceptible to antibiotic therapy. As well, aggressive therapy is often not possible, given the physical state of the AIDS patient being treated. A prudent strategy for AIDS is the use of certain drugs as a means of preventing infection, and to try to avoid those factors that place the individual at risk for acquiring atypical mycobacterial infections. Some risk factors that have been identified include the avoidance of unwashed raw fruit and vegetables. As well, contact with pigeons should be limited, since these birds are known to harbor atypical mycobacteria in their intestinal tracts.

See also Bacteria and bacterial infections; Immunodeficiency diseases

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Mycobacterium

Mycobacterium (order Actinomycetales) A genus of bacteria that typically form straight or curved, rod-shaped cells but also branched rods or fragile filaments. The genus includes many species, among which are several important pathogens. M. tuberculosis (the tubercle bacillus) causes tuberculosis in humans, other primates, dogs, and certain other animals. M. bovis (bovine tubercle bacillus) also causes tuberculosis, and is generally more pathogenic in cattle and various other animals than is M. tuberculosis. M. avium (avian tubercle bacillus) causes tuberculosis in birds, including domestic fowl. M. leprae causes leprosy in man. The genus also includes some saprotrophic species. M. phlei (timothy grass bacillus) is non-pathogenic and is found on grass and hay.

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Mycobacterial Infections, Atypical

Mycobacterial Infections, Atypical

What Are Atypical Mycobacterial Infections?

Are Atypical Mycobacterial Infections Common?

How Do People Know They Have an Atypical Mycobacterial Infection?

What Are Some Specific Infections?

How Do Doctors Diagnose and Treat Atypical Mycobacterial Infections?

Can People Prevent Atypical Mycobacterial Infections?

Resources

Atypical mycobacterial (my-ko-bak-TEER-e-ul) infections are infections caused by mycobacteria* other than those that cause tuberculosis*.

*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.

KEYWORDS

for searching the Internet and other reference sources

Mycobacteria other than tuberculosis (MOTT)

Mycobacterium avium complex (MAC)

Mycobacterium intracellulare

Mycobacterium kansasii

Mycobacterium marinum

Mycobacterium ulcerans

Opportunistic infections

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 persons 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.

*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.

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.

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 MOTT infection. In children, lymphadenitis* is the most common type of MOTT infection, whereas lung infections, which occur less often in children, are the most common in adults.

*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.

Exposure to Mycobacterium marinum can lead to a rare infection known as swimming pool granuloma or aquarium granuloma. About 3 weeks after the bacteria enters through a break in the skin, usually on the hands, reddish bumps appear. This infection can be prevented by avoiding contact with contaminated water and wearing gloves or washing thoroughly when cleaning aquariums. Custom Medical Stock Photo, Inc.

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.

*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.

Mycobacterium marinum

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.

*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.

Mycobacterium ulcerans

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.

Mycobacterium kansasii

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 patients 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.

*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.

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 persons 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.

*abscesses
(AB-seh-sez) are localized or walled off accumulations of pus caused by infection that can occur anywhere in the body.

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.

See also

AIDS and HIV Infection

Tuberculosis

Resources

Organizations

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

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"Mycobacterial Infections, Atypical." Complete Human Diseases and Conditions. . Retrieved December 18, 2017 from Encyclopedia.com: http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/mycobacterial-infections-atypical

Mycobacterium

Mycobacterium (my-koh-bak-teer-iŭm) n. a genus of rodlike aerobic Gram-positive bacteria. Several species are responsible for opportunistic infections of the lung (see MAI complex). M. leprae (Hansen's bacillus) the species that causes leprosy. M. tuberculosis (Koch's bacillus) the species that causes tuberculosis.

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