Nocardia: Difference between revisions
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Nocardia
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===Microbiology=== |
===Microbiology=== |
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*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]] |
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*Catalase [[Catalase::positive]] and lyzozyme resistant |
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*Has a classic beaded branching cell morphology |
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*Colonies are slow to grow and have a chalky white appearance |
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*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 |
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==Management== |
==Management== |
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Revision as of 12:53, 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
- Mild to moderate: TMP-SMX
- Immunocompetent: 5-10 mg/kg split tid to qid
- Immunocompromised: 15 mg/kg split tid to qid
- Severe: TMP-SMX plus either amikacin or imipenem
- Other antimicrobials include ceftriaxone, minocycline, and linezolid
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
