Nocardiosis

Nocardiosis is an acute, subacute, or chronic bacterial infection. It's caused by a weakly gram-positive species of the genus Nocardia - usually Nocardia asteroides. There are approximately 1.000 cases annually in the United States. The disease is more common among adults, especially males. Eighty-five percent of these cases are pulmonary or systemic, with the risk greater in individuals with different cell-mediated immunity, particularly those with lymphoma, transplantation, or acquired immunodeficiency syndrome.

Causes

Nocardia is a genus of aerobic, gram-positive bacteria with branching filaments similar in appearance to fungi. Normally found in soil, these organisms occasionally cause disease in humans and animals throughout the world. Their incubation period is unknown, but it is probably several weeks. The usual mode of contact is through soil or vegetable matter. Less often, transmission occurs by direct inoculation through puncture wounds or abrasions.

Signs and Symptoms

Most cases of nocardiosis begin as lung infections which develop into lung abscesses. Nocardiosis symptoms are similar to those of pneumonia and tuberculosis.

Symptoms may include:

• A vague feeling of discomfort or illness.
• Chest pain.
• Cough.
• Blood stained sputum (phlegm), containing mucus, saliva, and bacteria.
• Night sweats.
• Chills.
• Weakness.
• Lack of appetite.
• Weight loss.
• Difficulty in breathing.

Eventually the abscess may extend into the chest wall and invade the ribs. The infection may spread through the bloodstream causing abscesses in the brain and occasionally in the kidney, intestines or other organs.  Approximately one-third of cases develop brain abscesses. Symptoms associated with brain abscesses may include severe headache and disturbances of focal, sensory and motor functions.

Skin abscesses also occur in approximately one-third of cases. Skin abscesses are usually found on the hand, chest wall and buttocks.

Diagnostic tests

Identification of Nocardia is by culture of sputum or discharge for crooked, branching, beaded, gram-positive filaments with acid-fast smears. Because Nocardia can take up to 4 weeks to grow and culture, the laboratory.
should be alerted when Nocardia infection is suspected. Diagnosis occasionally requires biopsy of lung or other tissue. Chest X-rays vary and may show fluffy or interstitial infiltrates, nodules, or abscesses.

Computed tomography or magnetic resonance imaging of the head, with and without contrast, should be done if brain involvement is suspected. Cerebrospinal fluid (CSF) or urine should be concentrated and cultured. Several presumptive diagnostic tests are under study (antibody testing and metabolites for Nocardia in serum or CSF) but aren't yet used clinically.

Treatment

Nocardiosis is treated with sulfonamides as the treatment of choice; minocycline is an alternative to sulfonamides. If the patient fails to respond to sulfonamide treatment, other drugs, such as ampicillin or amikacin can be substituted. Immunosuppressive agents can also be considered if the underlying disease involves organ transplantation. Treatment also includes surgical drainage of abscesses and excision of necrotic tissue. The acute phase requires complete bed rest; as the patient improves, activity can increase.

Prevention

Caution when using corticosteroids may be helpful - these drugs should be used sparingly and in the lowest effective doses and for the shortest periods of time possible when they are needed.

Some patients with impaired immune systems may need to take antibiotics for long periods of time to prevent the infection from recurring.