Nocardiosis in transplant recipients.

Nocardia is an increasingly important opportunistic pathogen in immunosuppressed patients, especially solid organ transplant recipients. Infection is most often caused by Nocardia asteroides and presents as lung disease in 80% to 90% of infected transplant patients. Radiographic findings are nonspecific and include nodular infiltrates, cavitation, and pleural effusion. Dissemination to other organs, especially to the central nervous system (CNS) and skin, occurs in up to 40% of transplant recipients. A presumptive diagnosis is most rapidly made by the direct visualization in tissue, lower respiratory secretions, or wound drainage of filamentous, gram-positive, beaded rods that are partially acid fast. Specimens for culture should be held for at least 3 weeks when the diagnosis is suspected. The prognosis of nocardial infection is related to the site of disease, rapidity of diagnosis, and extended treatment with a sulfonamide. Mortality is highest in patients with CNS involvement. Prophylactic trimethoprim-sulfamethoxazole should be considered in transplant centers with excess rates of nocardial infection. Hopefully, future refinement of immunosuppressive regimens will be accompanied by a reduction in frequency of Nocardia infections in transplant recipients.