Nocardia bacteria are weakly-Gram positive, catalase positive aerobic bacteria belonging to the sub order Corynebacterineae of the Actinobacteria.
Nocardia are saprophytes and are present in soil, water or decaying organic material. The genus contain at least 25 species of which 13 are pathogenic (Nocardiosis) to humans in both immune-competent and immune-compromised individuals.
Nocardiosis is an acute, subacute, or chronic infectious disease that generally occurs in cutaneous, pulmonary and disseminated forms.
The primary cutaneous condition manifests as cellulitis, abscess or lymphocutaneous nocardiosis conditions.
Pleuropulmonary nocardiosis can be acute, subacute or chronic pneumonitis in immune-compromised patients as well as individuals on long-term corticosteroid therapy for lung disease.
Subcutaneous and lymphocutaneous infections arise from traumatic inoculation. The lymphocutaneous infection is accompanied with regional lymphoadenopathy and may drain purulent material.
N. asteroides and brasiliensis are causal in most cases of infection. Immune-compromised patients have been reported to have the following species associated with their infection: cyriacigeorgica (endocarditis), farcinica (adrenal glands), abscessus (grain abscess) and other infections (otitidiscavarium, transvalensis).
Cutaneous and systemic nocardiosis in patients with long-term corticosteroid therapy has been reported for the species brasiliensis and otitidiscavarium.
Toxigenic strains of Nocardia have been isolated from indoor environments of water-damaged buildings. These include N. exhalans, N. umidischolae, N. prasina, N. lucentensis, N. tropica and strain ES10.1. These organisms produced toxins that were toxic to mitochondria thorough dissipation of the mitochondrial membrane of boar spermatozoa.
For additional information:
Case Report: Nocardia asteroides Mycetoma.Annals of Clinical & Laboratory Science, vol. 33, no. 3, 2003. Read the paper.
Primary cutaneous nocardiosis with craniocerebral extension: A case report. Dermatology Online Journal 15 (6): 8.