Nocardia: Difference between revisions

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Nocardia
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*Microscopic appearance similar to [[Actinomyces]], differentiated by acid fast staining ([[Actinomyces]] is ''not'' acid fast)
 
*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
 
*Colonies are slow to grow and have a chalky white appearance
*Saprophyte found in soil and water
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*Ubiquitous environmental saprophyte found in soil and water
   
 
=== Pathophysiology ===
 
=== Pathophysiology ===
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* Spores or mycelia are either inhaled into the lungs or directly inoculated in the skin and soft tissue
 
* 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
 
* Traumatic inoculation includes during motor vehicle collisions, mild scratches or pricks, or nosocomial with dirt entering through an open wound or central line
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* Forms difficult-to-treat biofilms when involved in [[CLABSI|CLABSIs]]
   
 
=== Risk Factors ===
 
=== Risk Factors ===
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* Among transplant recipients, [[lung transplant]] appears to be highest risk
 
* 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
 
* High-dose steroids and high levels of [[calcineurin inhibitors]] appear to be specific risk factors
  +
* Also diabetes and alcohol use
   
 
== Clinical Manifestations ==
 
== Clinical Manifestations ==
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==Management==
 
==Management==
   
  +
=== Further Evaluation ===
  +
  +
* Consider screening MRI brain in all patients with disseminated or pulmonary disease regardless of neurologic symptoms
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* Consider CT chest in all patients
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* Consider assessment for immunodeficiency; at the very least, HIV testing and a good history
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  +
=== Antimicrobial Selection ===
 
*Mild to moderate: [[Is treated by::TMP-SMX]]
 
*Mild to moderate: [[Is treated by::TMP-SMX]]
 
**Immunocompetent: 5-10 mg/kg split tid to qid
 
**Immunocompetent: 5-10 mg/kg split tid to qid

Latest revision as of 18:05, 12 March 2023

Background

Microbiology

  • 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

Pathophysiology

  • 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

Pulmonary

  • 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

Disseminated

  • 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

Other

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

Management

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

Duration

  • 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

Monitoring

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