Actinomyces and Nocardia Species

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

  • Diagnosis
  • Background
  • Lab Tests
  • References
  • Related Topics

Indications for Testing

  • Pulmonary cavitary disease, cervicofacial abscesses

Laboratory Testing

  • CDC diagnosis information (2016)
  • Actinomycosis anaerobic culture
    • Specimen must be collected and transported under anaerobic conditions
    • May require aggressive collection methods (eg, needle biopsy, transbronchial biopsy)
  • Nocardiosis
    • Gram stain and modified acid-fast stain of sputum or infected material
    • Culture from infected site
      • May take up to 2 weeks to grow
      • Lab should be notified of suspicion so culture will be maintained for longer than usual 48-72 hours


  • 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, or consolidation

Differential Diagnosis


  • 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 intrauterine device (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

  • Actinomycosis
    • Alcoholism
    • Poor oral hygiene
    • Pulmonary form – emphysema, chronic bronchitis, bronchiectasis
  • Nocardiosis

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
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.

Anaerobe Culture and Gram Stain 0060143
Method: Stain/Culture/Identification

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

Nocardia Culture and Gram Stain 0060093
Method: Culture

General References

Brown-Elliott BA, Brown JM, Conville PS, Wallace RJ. Clinical and laboratory features of the Nocardia spp. based on current molecular taxonomy. Clin Microbiol Rev. 2006; 19(2): 259-82. PubMed

Martínez R, Reyes S, Menéndez R. Pulmonary nocardiosis: risk factors, clinical features, diagnosis and prognosis. Curr Opin Pulm Med. 2008; 14(3): 219-27. PubMed

Sullivan DC, Chapman SW. Bacteria that masquerade as fungi: actinomycosis/nocardia. Proc Am Thorac Soc. 2010; 7(3): 216-21. PubMed

Wilson JW. Nocardiosis: updates and clinical overview. Mayo Clin Proc. 2012; 87(4): 403-7. PubMed

Wong VK, Turmezei TD, Weston VC. Actinomycosis. BMJ. 2011; 343: d6099. PubMed

References from the ARUP Institute for Clinical and Experimental Pathology®

Barker AP, Simmon KE, Cohen S, Slechta S, Fisher MA, Schlaberg R. Isolation and identification of Kroppenstedtia eburnea isolates from multiple patient samples. J Clin Microbiol. 2012; 50(10): 3391-4. PubMed

Cloud JL, Conville PS, Croft A, Harmsen D, Witebsky FG, Carroll KC. Evaluation of partial 16S ribosomal DNA sequencing for identification of nocardia species by using the MicroSeq 500 system with an expanded database. J Clin Microbiol. 2004; 42(2): 578-84. PubMed

Khot PD, Bird BA, Durrant RJ, Fisher MA. Identification of Nocardia Species by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry J Clin Microbiol. 2015; 53(10): 3366-9. PubMed

Schlaberg R, Simmon KE, Fisher MA. A systematic approach for discovering novel, clinically relevant bacteria. Emerg Infect Dis. 2012; 18(3): 422-30. PubMed

Medical Reviewers

Last Update: October 2017