Actinomyces and Nocardia Species

Diagnosis

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
  • 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
  • CDC technical information on Nocardiosis, including diagnosis challenges

Histology

• 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

• Pulmonary manifestations
  • Bacteria
    • Mycobacteria spp
    • Gram-negative organisms
    • Rhodococcus equi
  • Lung abscess
  • Lung cancer
  • Fungal
    • Aspergillus
    • Cryptococcus
• Cervical-facial manifestations
  • Lymphadenitis
  • Neoplasm
    • Local – head and neck
    • Metastatic
  • Tonsillitis
  • Necrotic skin infection
  • Other odontogenic infections
• Abdominal manifestations
  • Appendicitis
  • Diverticulitis
  • Peptic ulcer disease
  • Foreign body/obstruction
  • Malignancy
  • Inflammatory bowel disease

Clinical Background

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

Epidemiology

• 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)

Organisms

• 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

• Actinomycosis
  • Alcoholism
  • Poor oral hygiene
  • Pulmonary form – emphysema, chronic bronchitis, bronchiectasis
• Nocardiosis
  • Alcoholism
  • Diabetes mellitus
  • HIV
  • Immunocompromised state – particularly solid organ transplant patients
  • Trauma

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