Nocardiosis

Overview

Nocardiosis is an uncommon infection caused by Nocardia, a group of bacteria that live in soil, dust, water, and decaying plant material. People usually become infected by breathing in the bacteria or when they enter a cut or wound in the skin. From there, the infection can stay local or spread through the bloodstream to other parts of the body.

The infection most often affects people whose immune systems are weakened, although it can occasionally occur in otherwise healthy people. The lungs are the most common site, but nocardiosis can also affect the skin and, importantly, the brain. Because it can be serious and spread, it usually requires a long course of antibiotics under medical care.

Symptoms

Symptoms depend on which part of the body is affected.

• Lung infection: Cough, sometimes with phlegm or blood, chest pain, fever, night sweats, weight loss, and shortness of breath.
• Skin infection: Sores, ulcers, abscesses, or nodules, sometimes spreading along the path of lymph channels after a scratch or wound.
• Brain infection: Headache, confusion, seizures, weakness, or other neurological symptoms if an abscess forms in the brain.
• Spread to other organs: Symptoms depending on the site involved.

Because symptoms can be slow to develop and resemble other infections, nocardiosis is sometimes diagnosed late.

Causes

Nocardiosis is caused by Nocardia bacteria found widely in the environment. People become infected mainly in two ways:

• Breathing it in: Inhaling dust or soil particles containing the bacteria, which can lead to lung infection.
• Skin entry: The bacteria entering through a cut, scratch, or puncture, often from contact with soil or plants.

Once in the body, the infection can stay where it started or travel through the bloodstream to organs such as the brain. Nocardiosis is not spread from person to person.

Risk Factors

• A weakened immune system, such as from HIV, organ transplant, or cancer treatment
• Long-term use of corticosteroids or other immune-suppressing medicines
• Chronic lung diseases
• Diabetes
• Close, frequent contact with soil and plants, such as in gardening or farming

Diagnosis

Diagnosing nocardiosis can be challenging and relies on laboratory identification of the bacteria.

• Samples for testing: Sputum, pus, tissue, or fluid from an affected area examined and cultured in the laboratory.
• Special stains and cultures: Needed because Nocardia can be slow to grow and easy to miss, so the lab is often told to look for it specifically.
• Imaging: Chest X-ray or CT for lung disease, and brain imaging such as CT or MRI to check for abscesses, especially in people with weakened immunity.

Treatment

Nocardiosis is treated with antibiotics, usually for a long period to fully clear the infection and prevent relapse.

• Antibiotics: Often a sulfonamide-based medicine, sometimes combined with others, chosen based on the type of Nocardia and the sites involved.
• Long treatment courses: Frequently several months or longer, especially when the brain or multiple sites are affected.
• Drainage or surgery: Abscesses may need to be drained.
• Managing immune factors: Adjusting immune-suppressing treatment where possible.

Because nocardiosis can be serious and slow to clear, treatment is often guided by an infectious disease specialist. The length of therapy depends on which parts of the body are involved and how strong the immune system is, with longer courses used when the brain is affected or immunity is weakened. Close follow-up is important to confirm the infection clears, to watch for side effects, and to make sure it does not return.

Prevention

There is no vaccine. Prevention focuses on reducing exposure, especially for people with weakened immune systems:

• Wear gloves and protective clothing when handling soil or doing gardening
• Clean cuts and wounds promptly and keep them covered
• Avoid heavy dust exposure when possible
• Manage underlying conditions and take immune-suppressing medicines only as prescribed
• Seek care early for persistent cough, skin sores, or other concerning symptoms if your immunity is reduced

When to See a Doctor

See a doctor if you have a persistent cough, fever, or skin sores that do not heal, particularly if your immune system is weakened. Seek emergency care for neurological warning signs that may suggest brain involvement, such as:

• Severe or worsening headache
• Confusion or change in alertness
• Seizures
• New weakness, numbness, or trouble speaking

Related Topics

Frequently Asked Questions

References

1. Centers for Disease Control and Prevention (CDC). Nocardiosis.
2. MedlinePlus, U.S. National Library of Medicine. Nocardia infection.
3. StatPearls, National Library of Medicine. Nocardiosis.
4. National Institute of Allergy and Infectious Diseases (NIAID).