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Nocardia / (Redirected from Nocardiosis)



  • Beaded Gram-positive partially acid-fast bacillus within the class Actinobacteria and order Corynebacteriales
  • Catalase positive and lyzozyme resistant
  • Has a classic beaded branching cell morphology
  • Microscopic appearance similar to Actinomyces, differentiated by acid fast staining (Actinomyces is not acid fast)
  • Colonies are slow to grow and have a chalky white appearance
  • Ubiquitous environmental saprophyte found in soil and water


  • Spores or mycelia are either inhaled into the lungs or directly inoculated in the skin and soft tissue
  • Traumatic inoculation includes during motor vehicle collisions, mild scratches or pricks, or nosocomial with dirt entering through an open wound or central line
  • Forms difficult-to-treat biofilms when involved in CLABSIs

Risk Factors

  • More common in immunocompromised (cell-mediated immunodeficiency including HIV, hematologic malignancy, and transplant patients), though can also occur in immunocompetent who have COPD, bronchiectasis, and cystic fibrosis
  • Among transplant recipients, lung transplant appears to be highest risk
  • High-dose steroids and high levels of calcineurin inhibitors appear to be specific risk factors
  • Also diabetes and alcohol use

Clinical Manifestations

Primary Cutaneous

  • Typically acquired by direct inoculation with soil
  • Nocardia brasiliensis is the most common cause in North America
  • May present with superficial soft tissue infection, including ulcer, abscess, cellulitis, pustules, plaques, or papules, most commonly on the arms and legs
  • Can progress to lymphocutaneous infection with sporotrichoid lesions


  • Subacute or chronic cough, dyspnea, fever, with or without pleuritic chest pain
  • Most common form of disease in US
  • Colonization also possible, particularly with patients who have structural lung changes like cystic fibrosis
  • Starts with inflammation followed by formation of granulomas and necrotic abscesses
  • Imaging typically showed lung nodules, lobar consolidation, and pleural effusion, and may show infiltrates and necrotizing granulomas
    • Usually bilateral
    • Cavitations more common in immunocompromised patients


  • Usually starts with a focal infection (skin or lung), which then disseminates hematogenously
  • Most commonly involves skin, lungs, and CNS, but can also disseminate to kidney, joint, retina, and heart
  • Much more common in immunosuppressed patients

CNS Disease

  • Most common site of hematogenous dissemination
  • Presents with typical symptoms of fever, headache, meningismus, seizure, and focal neurologic deficits
  • Can also be asymptomatic, so immunocompromised patients should get imaging and possibly LP


  • Mycetoma
  • Bacteremia
  • Ocular infection, either from direct inoculation or hematogenous spread
  • Bone and joint infection, primarily from dissemination


Further Evaluation

  • Consider screening MRI brain in all patients with disseminated or pulmonary disease regardless of neurologic symptoms
  • Consider CT chest in all patients
  • Consider assessment for immunodeficiency; at the very least, HIV testing and a good history

Antimicrobial Selection


  • Isolated cutaneous infection in immunocompetent host: 3 to 6 months
  • Isolated cutaneous infection in immunocompromised host: 6 to 12 months
  • Serious pulmonary infection: 6 to 12 months or longer
  • Any non-cutaneous disease in immunocompromised host: at least 12 months, and possibly lifelong suppression


  • Serial CT scans to assess response to therapy
  • Monitoring for antibiotic toxicity