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Updated 19 February 2016

Nocardiosis

Nocardiosis is an infectious disease, caused by bacteria of the nocardia family.

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Summary:
an infectious disease, caused by bacteria of the nocardia family, and either limited to the lungs or systemic (spread through the body).

Alternative names:
none

What is this?
An infection with nocardia bacteria, usually nocardia asteroides, or nocardia brasiliensis, and is more common in men, especially if they have a weakened immune system.

What causes this?
Nocardia bacteria are found in the soil, and the infection is spread by inhaling them in dust in the air. They cause occasional mild infections in humans and animals in many parts of the world, and serious illness when they reach someone with much reduced immunity, including someone with HIV/Aids or transplant recipients, or those on long-term steroid therapy for other reasons. Chronic smokers may also be at increased risk.

What are its symptoms?
In a chest infection, symptoms include fever, night sweats, cough, and chest discomfort, and it does not respond to the usual forms of antibiotic treatment for chest infections. There tend to be multiple lung abscesses. It can spread to the nervous system, causing confusion, weariness, seizures, headache and other neurological signs. It can cause skin infections and swellings of the lymph nodes. In the more systemic variety, in patients with little normal immunity, it usually involves lungs, kidneys (with urinary infection) , liver (with abdominal pain) and brain, with fever and brain abscesses ; and les often, may spread to the heart, eyes, joints and bones. The severity of the illness tends to wax and wane.

How is it diagnosed?
Diagnosis can be difficult, and the infection can mimic infections such as tuberculosis. Careful microscopic examination to identify the organism is needed, searching relevant body fluids such as sputum, and pus from abscesses, and biopsies from infected areas may help. It may be possible to grow the organism in the laboratory, but this can take up to three weeks. X-rays and scans may help locate abscesses.

How is it treated?
At least six months of treatment is needed, usually with co-trimoxazole or high dose sulfonamodes, intravenously. Linezolid given orally can be very effective. Where response to these is limited, other antibiotics may be tried, including ampicillin, erythromycin, or others. Surgical drainage of abscesses is useful and can aid the diagnosis, too. Antibiotic treatment may need to be prolonged.

What is the prognosis?
It is a serious infection with a mortality of around 50% even with competent treatment, and where the infection has spread to the brain, the mortality is over 80%. In patients with Aids, the infection may reasserts itself after a considerable time.

When to call your doctor
When the relevant symptoms arise in someone with reduced immunity.

How can it be prevented?
Not practical, as this is an opportunistic infection in vulnerable patients. Where co-trimoxazole is used to prevent pneumocystis infections, it may also to some degree protect against nocardiosis.

Copyright M. A. Simpson, 2008

 
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