Actinomyces and Nocardia Species


Indications for Testing

  • Pulmonary cavitary disease, cervicofacial abscesses

Laboratory Testing

  • Actinomycosis anaerobic culture
    • Specimen must be collected and transported under anaerobic conditions
    • May require aggressive collection methods (eg, needle biopsy, transbronchial biopsy)
  • Nocardiosis


  • Actinomycosis
    • Sulphur granules occasionally noted in infected material

Imaging Studies

  • Chest x-ray
    • Actinomycosis
      • Cavitation coupled with soft-tissue swelling and rib involvement
      • Most common in lower lobes
    • Nocardiosis
      • Cavitation
      • May appear as masses, nodules, consolidation

Differential Diagnosis

Clinical Background

Actinomyces and Nocardia species are the causative agents of actinomycosis and nocardiosis. These are often considered when patients develop indolent granulomatous diseases.


  • Incidence
    • Actinomycosis – 1-2/300,000
    • Nocardiosis – <1/300,000
  • Age
    • Actinomycosis – peaks in 40s-50s
    • Nocardiosis – all ages, but rare in children
  • Sex
    • Actinomycosis – M>F, 3:1
    • Nocardiosis – M>F
  • Transmission
    • Actinomycosis
      • Mucosal barrier disruption with contiguous spread
      • Aspiration
    • Nocardiosis – inhalation or direct inoculation (eg, penetrating injury)


  • Actinomyces
    • Facultative anaerobe
      • Gram-positive
      • Nonspore forming
      • Commensal of the human oropharynx gastrointestinal tract and female genitalia
    • Disease most commonly caused by Actinomyces israelii
      • Infection may be associated with IUD use
    • Most infections are polymicrobial
  • Nocardia
    • Aerobic genus of the order Actinomycetaceae
      • Gram-positive
      • Weakly acid-fast
      • Soil saprophytes
    • Disease mainly caused by species in the former Nocardia asteroides complex
      • Most commonly Nocardia cyriacigeorgica

Risk Factors

Clinical Presentation

  • Actinomycosis
    • Usually insidious onset with constitutional symptoms – fever, anorexia, malaise, weight loss
    • Oral-cervicofacial – most frequent location
      • Soft tissue swelling, abscess, or mass lesion
        • Most common in premandibular region
        • Sinus tract infections occur frequently
    • Thoracic disease
      • Slowly progressive pneumonia
      • May also involve pleura, mediastinum, chest wall, pericardium
    • Abdominal disease
      • Appendicitis, perirectal disease, hepatic infection, pelvic disease, renal disease
  • Nocardiosis
    • Predominantly causes pneumonia
      • Irregular nodular disease
      • May progress to cavitary disease
      • Process may resemble tuberculosis
    • Disseminated disease common
      • Cerebral abscess – occurs in ~30% of patients with pulmonary disease
      • Other sites – eyes, kidney, bones, joints, heart
    • Skin and soft tissue infections, lymphadenitis – usually result from trauma
    • Bacteremia – often catheter-related
    • Peritonitis – usually peritoneal dialysis catheter-related
    • Local spread of disease – chest wall, soft tissue masses, bone destruction, external fistulas

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
Anaerobe Culture and Gram Stain 0060143
Method: Stain/Culture/Identification
Use to diagnose actinomycoses infection

Specimen must be collected and transported under anaerobic conditions

Acid Fast Stain, Partial or Modified (for Nocardia spp.) 0060325
Method: Stain/Microscopy

Use to detect actinomycetes (Nocardia and Gordonia spp, etc)

Nocardia Culture and Gram Stain 0060093
Method: Culture

Diagnose Nocardia infection

Also detects other actinomycetes (Streptomyces, Rhodococcus, Gordona, Tsukamurella, etc)