Nocardia.

N asteroides is an aerobic, gram-positive, partially acid-fast, branching rod. Cell-mediated immunity via both macrophage activation and direct cytotoxicity represents the main host defense. While clinical infection most commonly occurs in immunocompromised hosts, Nocardia can infect and exist as a saprophyte in normal hosts. Diligence on the part of the treating physician is necessary to confirm the diagnosis. A combination of trimethoprim and sulfamethoxazole is the mainstay of treatment. With an aggressive approach to diagnosis and therapy, the prognosis in patients with nocardiosis appears to be dependent on their underlying disease process.