Nocardiosis

Nocardiosis is an acute, subacute, or chronic bacterial infection caused by weakly gram-positive bacilli of the genus Nocardia—usually Nocardia asteroides. It can occur in cutaneous, lymphocutaneous, and subcutaneous forms following local traumatic inoculation. Dissemination from these sites is more likely in immunocompromised hosts. Pleuropulmonary nocardiosis is thought to arise from inhalation exposure. Disseminated nocardiosis is spread first through the bloodstream, usually from a pulmonary focus, and then to the central nervous system (CNS) or skin. Most persons with disseminated disease are immunocompromised or receiving immunosuppressive therapy.

Causes

Nocardia are aerobic bacilli with branching filaments that resemble fungi. Normally found in soil, these opportunistic pathogens cause occasional sporadic disease in humans and animals throughout the world. Their incubation period is unknown but is probably several weeks. The usual mode of transmission is inhalation of organisms suspended in dust. Transmission by direct inoculation through puncture wounds or abrasions is less common.

Complications

Complications include meningitis, seizures, and cardiac arrhythmias. Other potential complications include tracheitis, bronchitis, pericarditis, endocarditis, peritonitis, mediastinitis, septic arthritis, and keratoconjunctivitis.

Assessment Findings

The physical findings in patients with nocardiosis will vary depending on the site of infection and extent of dissemination. Nocardiosis originating as a pulmonary infection produces a cough with thick, tenacious, purulent, mucopurulent, and possibly blood-tinged sputum. It may also cause a fever as high as 105° F (40.6° C), chills, night sweats, anorexia, malaise, and weight loss. This infection may lead to pleurisy, intrapleural effusions, and empyema.

If the infection spreads through the blood to the brain, abscesses form, causing confusion, disorientation, dizziness, headache, nausea, and seizures. Rupture of a brain abscess can cause purulent meningitis. Extrapulmonary, hematogenous spread may cause endocarditis or lesions in the kidneys, liver, subcutaneous tissue, and bone.

Cutaneous nocardiosis may present as a cutaneous, lymphocutaneous, or subcutaneous infection. Cutaneous nocardiosis manifests with symptoms of cellulitis or nontender erythematous nodules at the site of traumatic inoculation. These nodules may drain purulent material. Lymphocutaneous nocardiosis is evident by lesions with ascending regional lymphadenopathy, which may also drain purulent material. In tropical areas of the world, mycetoma of the extremities may occur as a chronic, swollen, purulence-draining, subcutaneous infection.

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