Atypical mycobacterial infection

Definition

Atypical mycobacterial infection is an infection caused by a species of mycobacterium other than tuberculosis.

Causes, incidence, and risk factors

Atypical mycobacteria can cause a wide variety of infections such as abscesses, septic arthritis and osteomyelitis (bone infection). They can also can infect the lungs, lymph nodes, gastrointestinal tract, skin and soft tissues.

There are many different species of mycobacterium other than tuberculosis (Mycobacterium tuberculosis). Some of the most common are listed below:

• M. avium-intracellulare
• M. marinum
• M. ulcerans
• M. kansasii

M. avium-intracellulare frequently affects AIDS patients, often causing fever, lymphadenopathy (swollen lymph nodes), and diarrhea. M. avium intracellulare and M. kansasii cause lung disease.

M. marinum and M. ulcerans cause skin infections. M. marinum is also responsible for swimming pool granuloma.

The incidence of atypical mycobacterial infections is rare, but it is increasing as the AIDS population grows. Populations at risk include individuals with pre-existing lung disease and immunocompromised (immunosuppressed) persons.

Symptoms

• Fever
• Weight loss
• Enlarged lymph glands
• Diarrhea
• Sweating, excessive -- night sweats
• Fatigue
• General discomfort, uneasiness or ill feeling (malaise)
• Cough
• Shortness of breath (dyspnea)
• Skin lesions
• Joint pain
• Bone pain

• Paleness
• Flank pain

Signs and tests

Tests to determine infection:

• A blood culture using special techniques to detect mycobacterium
• A sputum culture with special stains
• A lymph node culture or biopsy with special stains
• A bone marrow culture with special stains
• A stool culture with special stains
• A chest X-ray or CT scan

Treatment

Treatment of the infection depends upon the sensitivity of the infecting organism to specific antibiotics. As many as 4-6 drugs may be used to treat some infections and treatment may require 6 months to 2 years.

Certain lymph node infections and skin lesions can be surgically removed. Treatment in immunocompromised (immunosuppressed) patients may require even more extended periods of medication use.

Expectations (prognosis)

The outcome depends upon the severity of the infection, the resistance of the organism, the individual's immune status and, ultimately, the response to treatment.

Calling your health care provider

Call for an appointment with your health care provider if symptoms develop that indicate an atypical mycobacterial infection may be present. HIV-positive individuals who develop a cough, rapid breathing (tachypnea), shortness of breath, or other pulmonary symptoms should see their health care provider immediately.

Prevention

Use of azithromycin or clarithromycin in AIDS patients with CD4 counts less than 50 may help to prevent this infection.

Illustrations

Mycobacterium marinum infection on the hand

Antibodies

Page Content:

Mycobacteria other than tuberculosis; Nontuberculous atypical mycobacterial disease