Nocardia: Difference between revisions

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Nocardia
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===Microbiology===
 
===Microbiology===
   
*Beaded [[Stain::Gram-positive]] [[Stain::partially acid-fast]] [[Shape::bacillus]]
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*Beaded [[Stain::Gram-positive]] [[Stain::partially acid-fast]] [[Shape::bacillus]] within the class [[Class::Actinobacteria]] and order [[Order::Corynebacteriales]]
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*Catalase [[Catalase::positive]] and lyzozyme resistant
*Appearance similar to [[Actinomyces]], differentiated by acid fast staining ([[Actinomyces]] is ''not'' acid fast)
 
  +
*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
  +
*Saprophyte found in soil and water
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  +
=== Pathophysiology ===
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  +
* Spores or mycelia are either inhaled into the lungs or directly inoculated in the skin and soft tissue
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* 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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  +
=== Risk Factors ===
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* 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]]
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* Among transplant recipients, lung transplant appears to be highest risk
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* High-dose steroids and high levels of celcineurin inhibitors appear to be specific risk factors
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== Clinical Manifestations ==
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=== Primary Cutaneous ===
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* Typically acquired by direct inoculation with soil
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* [[Nocardia brasiliensis]] is the most common cause in North America
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* May present with superficial soft tissue infection, including ulcer, abscess, cellulitis, pustules, plaques, or papules, most commonly on the arms and legs
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* Can progress to lymphocutaneous infection with [[sporotrichoid lesions]]
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=== Pulmonary ===
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* Subacute or chronic cough, dyspnea, fever, with or without pleuritic chest pain
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* Most common form of disease in US
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* Colonization also possible, particularly with patients who have structural lung changes like [[cystic fibrosis]]
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* Starts with inflammation followed by formation of granulomas and necrotic abscesses
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* Imaging typically showed lung nodules, lobar consolidation, and pleural effusion, and may show infiltrates and necrotizing granulomas
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** Usually bilateral
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** Cavitations more common in immunocompromised patients
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=== Disseminated ===
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* Usually starts with a focal infection (skin or lung), which then disseminates hematogenously
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* Most commonly involves skin, lungs, and CNS, but can also dissemiante to kidney, joint, retina, and heart
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* Much more common in immunosuppressed patients
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=== CNS Disease ===
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* Most common site of hematogenous dissemination
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* Presents with typical symptoms of fever, headache, meningismus, seizures, and focal neurologic deficits
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* Can also be asymptomatic, so immunocompromised patients should get imaging and possibly LP
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=== Other ===
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* [[Mycetoma]]
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* Bacteremia
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* Ocular infection, either from direct inoculation or hematogenous spread
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* Bone and joint infection, primarily from dissemination
   
 
==Management==
 
==Management==

Revision as of 08:53, 5 November 2022

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
  • 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

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 celcineurin inhibitors appear to be specific risk factors

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 dissemiante 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, seizures, 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

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