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.
Nocardia infection develops when you inhale the bacteria. The causes pneumonia-like symptoms but is often not limited to the lungs. Infection can spread to any part of the body, but brain and skin infections are the most common complications.
People at highest risk for nocardia infection are people with impaired immune systems, including people with HIV, people receiving chronic therapy with steroid medication, and people who have received organ transplants. People suffering chronic lung problems related to smoking, emphysema, or other infections such as tuberculosis are also at increased risk.
Symptoms and Signs
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.
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.
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.
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