Atypical Mycobacterial Infection

Overview

Atypical mycobacterial infections, also called nontuberculous mycobacterial (NTM) infections, are caused by a large group of mycobacteria that live naturally in soil, water, and dust. These bacteria are related to the ones that cause tuberculosis and leprosy, but they are different organisms and behave differently.

Unlike tuberculosis, most atypical mycobacterial infections are not spread from person to person. People usually become infected through contact with the environment, such as breathing in the bacteria or having them enter the skin through a wound. The infections can affect the lungs, the skin and soft tissue, or the lymph nodes, and they are more likely in people with certain lung conditions or weakened immunity. Treatment often requires a long course of several antibiotics.

Symptoms

Symptoms depend on which part of the body is affected.

• Lung infection: Chronic cough, sometimes with phlegm or blood, fatigue, fever, night sweats, weight loss, and shortness of breath.
• Skin and soft tissue infection: Nodules, ulcers, or abscesses, often after a skin injury or exposure to water.
• Lymph node infection: Swollen lymph nodes, especially in the neck, most often in young children.
• Widespread infection: Fever, weight loss, and other symptoms in people with severely weakened immune systems.

Symptoms often develop slowly, and lung disease can be mistaken for other chronic chest conditions.

Causes

These infections are caused by nontuberculous mycobacteria that are common in the environment. People are exposed regularly, but infection is uncommon and usually occurs when there is a route of entry or reduced defenses. Common ways of acquiring infection include:

• Inhaling bacteria from water droplets, soil, or dust, which can lead to lung infection.
• Skin entry through cuts, wounds, or procedures, leading to skin and soft tissue infection.
• Swallowing bacteria, which may contribute to lymph node infection in children.

Most types do not spread from person to person.

Risk Factors

• Chronic lung diseases, such as bronchiectasis or COPD
• A weakened immune system, including advanced HIV
• Older age
• Previous lung infections or damage
• Skin injuries with exposure to soil or water
• Certain body types and conditions associated with NTM lung disease

Diagnosis

Diagnosis requires identifying the specific mycobacteria and confirming they are causing disease, since these bacteria can sometimes be present without causing infection.

• Samples for testing: Sputum, tissue, fluid, or pus cultured in the laboratory, often more than once.
• Special stains and cultures: Because mycobacteria grow slowly and need specific methods.
• Imaging: Chest X-ray or CT for lung disease.
• Identifying the species: Which helps guide which antibiotics to use.

Distinguishing these infections from tuberculosis is important because treatment differs.

Treatment

Treatment depends on the type of mycobacteria, the site of infection, and the person's health. Not every positive test needs treatment, since some findings reflect harmless presence rather than active disease.

• Combination antibiotics: Usually several drugs taken together for many months to avoid resistance and clear the infection.
• Long treatment courses: Often a year or more for lung disease, with monitoring for side effects.
• Surgery or drainage: Sometimes used for infected lymph nodes, abscesses, or limited, severe lung disease.
• Treating underlying conditions: Such as managing lung disease or immune problems.

Because treatment is long and the medicines can have side effects, the decision to treat balances the benefits against the burdens, and it is often made with a specialist. Some people with mild findings are monitored over time rather than treated right away. Close follow-up with repeat samples and imaging is needed to track the response, manage side effects, and decide when treatment can stop.

Prevention

Because these bacteria are widespread, infection cannot always be prevented, but some steps may lower the risk for people who are vulnerable:

• Clean and cover skin wounds, especially before contact with soil or water
• Manage chronic lung conditions well
• Reduce exposure to aerosolized water sources if advised by your clinician
• Seek care early for a persistent cough or non-healing skin lesion if you are at higher risk

When to See a Doctor

See a doctor if you have a persistent cough, unexplained fatigue, fever, night sweats, or weight loss, or a skin lesion or swollen lymph node that does not heal, especially with a chronic lung condition or weakened immunity. Seek prompt care if you have:

• Coughing up blood
• Worsening shortness of breath
• High fever with feeling very unwell
• A rapidly spreading skin infection

Related Topics

Frequently Asked Questions

References

1. Centers for Disease Control and Prevention (CDC). Nontuberculous Mycobacteria (NTM) Infections.
2. American Thoracic Society. Nontuberculous mycobacterial disease.
3. MedlinePlus, U.S. National Library of Medicine.
4. National Institute of Allergy and Infectious Diseases (NIAID).