nocardiosis, chronic systemic bacterial disease of humans and many other animals originating in the respiratory tract and disseminated by way of the blood to other organs, especially the brain. It is caused either by introduction into the skin or by inhalation of Nocardia asteroides, a normal inhabitant of soil and compost heaps. Nocardiosis is an uncommon disease that is found worldwide. It most often occurs as an opportunistic infection in susceptible individuals, such as those with chronic lung disease or persons with weakened immune systems, which may be associated with chronic disease or immunosuppressive therapy.
Nocardiosis usually begins with malaise, weight loss, fever, and night sweats. Most often it causes a cough productive of purulent and blood-tinged sputum (pseudotuberculosis). Prolonged treatment with sulfonamide drugs, especially when begun before the disease has spread, can reduce mortality from nocardiosis greatly. If the organism has reached the brain, however, the outlook usually is very poor. Amikacin, an antibiotic, may be used with patients who do not respond to sulfa drugs.