Nocardia: Difference between revisions

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Nocardia
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{{DISPLAYTITLE:''Nocardia''
  
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[[Category:Gram-positive bacilli]]
  
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==Background==
  
==Background==
   
 
===Microbiology===
  
===Microbiology===
   
−
*Beaded [[Stain::Gram-positive]] [[Stain::partially acid-fast]] [[Shape::bacillus]]
 +
*Beaded [[Stain::Gram-positive]] [[Stain::partially acid-fast]] [[Shape::bacillus]] within the class [[Class::Actinobacteria]] and order [[Order::Corynebacteriales]]
  +
*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
  +
*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 [[CLABSI|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==
  
==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 ===
 
*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
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* Serious pulmonary infection: 6 to 12 months or longer
  
* Serious pulmonary infection: 6 to 12 months or longer
 
* Any non-cutaneous disease in immunocompromised host: at least 12 months, and possibly lifelong suppression
  
* 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{{DISPLAYTITLE:''Nocardia''}}
  ⚫
[[Category:Gram-positive bacilli]]

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
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