Mycobacterium avium
| Mycobacterium avium-intracellulare infection | |
|---|---|
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| CT scan of patient with right middle lobe aspiration and Mycobacterium avium infection consistent with Lady Windermere syndrome | |
| Classification and external resources | |
| Specialty | infectious disease |
| ICD-10 | A31.0 |
| ICD-9-CM | 031.0 |
| DiseasesDB | 29182 |
| eMedicine | med/1532 |
| MeSH | D015270 |
| Mycobacterium intracellulare | |
|---|---|
| Scientific classification | |
| Kingdom: | Bacteria |
| Phylum: | Actinobacteria |
| Order: | Actinomycetales |
| Suborder: | Corynebacterineae |
| Family: | Mycobacteriaceae |
| Genus: | Mycobacterium |
| Species: | M. avium |
| Binomial name | |
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Mycobacterium avium |
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Mycobacterium avium-intracellulare infection (MAI) is an atypical mycobacterial infection, i.e. one with nontuberculous mycobacteria or NTM, caused by Mycobacterium avium complex. This infection causes respiratory illness in birds, pigs, and humans, especially in immunocompromised people. In the later stages of AIDS it can be very severe. It usually first presents as a persistent cough. It is typically treated with a series of three antibiotics for a period of at least six months.
Mycobacterium avium and M. intracellulare (the M. a. complex, or MAC) are saprotrophic organisms present in soil and water; entry into hosts is usually via the gastrointestinal tract, but also can be via the lungs.
MAC can cause fevers, diarrhea, malabsorption, as well as loss of appetite and weight loss, and can disseminate to the bone marrow. Therapy for MAI is typically resistant to standard mycobacterial therapies.
Symptoms are similar to tuberculosis (TB), and include fever, fatigue, and weight loss. Pulmonary involvement is similar to TB, while diarrhea and abdominal pain are associated with gastrointestinal involvement.
M. avium and M. haemophilum infections in children form a distinct clinical entity, not associated with abnormalities of the immune system. M. avium typically causes unilateral swelling of one of the lymph nodes of the neck. This node is firm at the beginning, but a collarstud abscess' is formed eventually, which is a characteristic blue-purple in colour with multiple discharging sinuses. The treatment of choice is surgical excision of the affected lymph nodes, with antibiotic treatment (usually clarithromycin and rifabutin for 18 to 24 months) reserved for those patients who cannot have surgery.
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