|
Clinical
Features |
Overall, 80% of cases present as
invasive pulmonary infection, disseminated disease, or brain
abscess; 20% present as cellulitis. For pulmonary diseases
common symptoms are fever, cough, and chest pain; for central
nervous system disease symptoms are usually headache, lethargy,
confusion, seizures, and sudden onset of neurologic deficit.
|
Etiologic
Agent |
Nocardia asteroides (causes
at least 50% of invasive infections). Other pathogenic species
include N. farcinica, N. nova, N.transvalensis, N. brasiliensis,
and N. pseudobrasiliensis. |
Incidence |
In the United States, an estimated
500-1,000 new cases of Nocardia infection occur annually.
An estimated 10%-15% of these patients also have HIV infection. |
Sequelae |
Approximately 10% of cases with
uncomplicated pneumonia are fatal. Case-fatality rate increases
with overwhelming infection, disseminated disease, or brain
abscess. Surgical drainage may be indicated and may improve
patient outcome. |
Transmission |
Pulmonary and disseminated infections
occur through inhalation and primary cutaneous disease through
soil-contaminated wounds. Rarely, nosocomial postsurgical
transmission occurs. |
Risk
Groups |
Severely immunocompromised persons
(e.g., persons with malignancy, connective tissue disorders,
bone marrow or solid organ transplantation, high-dose corticosteroid
use, or HIV infection), alcoholism or pulmonary alveolar proteinosis,
and males (ratio male:female = 3:1) |
Surveillance |
No disease-specific surveillance
is conducted. |
Trends |
Although incidence data are extremely
limited, the number of cases probably has increased recently
because of the overall increased number of severely immunocompromised
persons. |
Challenges |
Diagnosis may be difficult. In
the clinical laboratory, routine cultures may be held for
insufficient time to grow nocardiae, and referral to a reference
laboratory may be needed for species identification. Recently,
N. farcinica and N. nova have been removed from
N.asteroides complex. N. farcinica frequently
is more resistant to antimicrobial agents, including trimethoprim-sulfamethoxazole
(TMP-SMX) (the drug of choice), and has been shown to be more
virulent in an animal model. TMP-SMX therapy for HIV-infected
patients may be complicated by frequent occurrence of side
effects and drug resistance. |
Opportunities |
A new combination drug therapy
(sulfonamide, ceftriaxone, and amikacin) has shown promise
for infections difficult to treat. Application of newer molecular
diagnostic and subtyping methods may assist in earlier diagnosis
and outbreak investigation. In 1998 MSPB described a rapid
PCR-based method to differentiate N. farcinica from
other nocardiae. |
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December 2003
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