Clinical Overview of Nocardiosis

Etiology

More than 40 Nocardia species are considered clinically relevant. The most commonly reported species from clinical sources are:

• Nocardia nova
• Nocardia farcinica
• Nocardia cyriacigeorgica
• Nocardia brasiliensis
• Nocardia abscessus

Who is at risk

People with very weak immune (body defense) systems are at risk for getting nocardiosis. Several diseases and conditions can cause the immune system to be weak. These include:

• Diabetes
• Cancer
• HIV/AIDS
• Pulmonary alveolar proteinosis (an illness that causes the air sacs of the lungs to become plugged)
• Connective tissue disorder (a disease that affects the tissue that connects and supports different parts of the body)
• Alcoholism
• Having a bone marrow or solid organ transplant
• Taking high doses of drugs called corticosteroids

In addition, men have a greater risk of getting the infection than women; for every female who gets sick with nocardiosis, there are about 3 males who get the disease.

Disease rates

In the United States, there are approximately 500-1,000 new cases of nocardiosis infection every year. Approximately 60% of nocardiosis cases are associated with pre-existing immune compromise.

Although incidence data are extremely limited, the number of cases is likely rising. This may be as a result of the increase in the number of severely immunocompromised people.

Clinical features

Pulmonary infection commonly presents with fever, cough, or chest pain, pneumonia, lung abscesses, or cavitary lesions.

Central nervous system (CNS) symptoms include:

• Headache
• Lethargy
• Confusion
• Seizures
• Sudden onset of neurologic deficit

Contiguous spread within the thoracic cavity and hematogenous dissemination, particularly to the CNS, are possible.

Overall, 80% of nocardiosis cases present as invasive lung infection, disseminated infection, or brain abscess; 20% present as cellulitis. About 10% of cases with uncomplicated pneumonia are fatal. Fatality rates are even higher - up to 80 percent- for brain or central nervous system infections.

Testing and diagnosis

Nocardiosis confirmation must be accomplished by laboratory testing.

Because it can take extended incubation time to isolate Nocardia from primary clinical specimens, infections are often overlooked. Routine cultures must be held for at least 14 days.

Accurate identification of Nocardia species requires molecular methods. Referral of isolates to a reference laboratory, such as CDC's Special Bacteriology Reference Laboratory, may be needed for identification and antimicrobial susceptibility testing.

For more information on laboratory diagnostics for Nocardia species and other aerobic actinomycetes, see the references below.

For information on laboratory submissions, visit Home | Submitting Specimens to CDC | Infectious Diseases Laboratories. All submissions from within the United States must be approved by the health department.

For faster and more accurate pathogen identification, go to MicrobeNET [Access Request Required].

Treatment and recovery

Nocardiosis is treatment with commonly available antibiotics. Surgical intervention is not usually indicated. However, it may be necessary for cerebral and soft tissue abscesses that do not respond to antibiotic treatment. In addition, empyema, mediastinal, and pericardial fluid collection drainage is often needed.

Some nocardiae are reported to have species-specific antibiotic susceptibility profiles and multidrug-resistant strains are common. For example, N. farcinica is often resistant to multiple antimicrobial agents, including trimethoprim-sulfamethoxazole (TMP-SMX). Because of this, antimicrobial susceptibility testing (AST) should be performed on every isolate of clinical significance.

CDC's Special Bacteriology Reference Laboratory performs AST on all isolates received.