MICROBIOLOGY

Nocardiae are branching, beaded, gram-positive filaments that usually give positive results with modified acid-fast stains. These saprophytic aerobic actinomycetes are common in soil.

• Nine species or species complexes are most commonly associated with human disease.
• Speciation of nocardiae is precluded in most clinical laboratories, although improvements in mass spectrometry–based techniques may change this limitation in high-resource countries.
• Nocardia brasiliensis is most often associated with localized skin lesions.