Burkholderia pseudomallei: Difference between revisions
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Burkholderia pseudomallei
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*Can occasionally lay latent and reactivate decades after exposure |
*Can occasionally lay latent and reactivate decades after exposure |
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===Prognosis and Complications=== |
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*50% mortality even with high-quality care |
*50% mortality even with high-quality care |
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**Blood, throat, and urine cultures should be taken from ''all'' patients with suspected melioidosis |
**Blood, throat, and urine cultures should be taken from ''all'' patients with suspected melioidosis |
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**Grows on blood agar, MacConkey, etc. (i.e. ''not'' a fastidious organism) |
**Grows on blood agar, MacConkey, etc. (i.e. ''not'' a fastidious organism) |
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**Can use selective colistin or polymyxin B |
**Can use selective colistin or polymyxin B, since it is inherently resistant |
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**On sheep blood agar, grows as small, smooth, cream-coloured colony with metallic sheen |
**On sheep blood agar, grows as small, smooth, cream-coloured colony with metallic sheen |
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**May develop a dry and '''wrinkled''' appearance after 1 to 2 days of incubation |
**May develop a dry and '''wrinkled''' appearance after 1 to 2 days of incubation |
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*MALDI-ToF may misidentify it as [[Burkholderia thailandensis]], and automated biochemical tests may misidentify it as [[Chromobacterium violaceum]] |
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*MALDI-ToF is ''not'' reliable for identifying it |
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*Other methods |
*Other methods |
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**PCR |
**PCR |
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Revision as of 11:00, 29 August 2020
Background
- Also called melioidosis or Whitmore's disease
Microbiology
- Oxidase positive, indole negative Gram-negative bacillus with "safety pin" appearance (i.e. bipolar staining)
- Non-hemolytic
- Colonies start small, smooth, cream-coloured with a metallic sheen, but become dry and wrinkly after 1 to 2 days of incubation
- Inherently resistant to polymixins
Epidemiology
- Humans and animals
- Important cause of death in south-east Asia and northern Australia
- Up to 80% seroprevalence in Thailand, mostly asymptomatic
- More cases during the rainy season
- Sporadic cases elsewhere, including the Middle East, Africa, and the Americas
- May have latent disease with reactivation much later
- Acquired by percutaneous inoculation, inhalation (esp. lab workers), and ingestion
- Risk factors for clinical disease
- Diabetes
- Heavy alcohol use
- Chronic lung disease
- Chronic kidney disease
- Treatment with glucocorticoids
- Cancer
- Thalassemia
Clinical Manifestations
- Incubation period 9 days (range 1 to 21 days)
- Presentations can vary from asymptomatic, skin ulcers, abscesses, latent infection, chronic pneumonia (similar to TB), or fulminant shock1
- Pneumonia (50%)
- Genitourinary infection (15%)
- Skin infection (15%), with ulcers, nodules, or abscesses
- Primary bacteremia (10%)
- Septic arthritis/OM (3-5%)
- Neuro (3-5%)
- Disseminated infections can involve liver, spleen, lung, and prostate
- About 50% of clinical cases have bacteremia, and 20% of cases will develop septic shock
- Can occasionally lay latent and reactivate decades after exposure
Prognosis and Complications
- 50% mortality even with high-quality care
Diagnosis
- Culture
- Blood, throat, and urine cultures should be taken from all patients with suspected melioidosis
- Grows on blood agar, MacConkey, etc. (i.e. not a fastidious organism)
- Can use selective colistin or polymyxin B, since it is inherently resistant
- On sheep blood agar, grows as small, smooth, cream-coloured colony with metallic sheen
- May develop a dry and wrinkled appearance after 1 to 2 days of incubation
- MALDI-ToF may misidentify it as Burkholderia thailandensis, and automated biochemical tests may misidentify it as Chromobacterium violaceum
- Other methods
- PCR
- Immunofluorescence and latex agglutination
- Serology (acute/convalescent)
Management
- Intrinsic resistance to many antibiotics, including colistin, primarily using efflux pumps
- Treat with induction followed by eradication therapy
- Induction: ceftazidime, imipenem, or meropenem for 10-14 days
- Eradication: TMP-SMX for 3+ months
- Others: amoxicillin-clavulanic acid
Prevention
Biosafety
- Lab workers can have aerosol exposure
- May need prophylaxis in high-risk patients
- Monitor with serology at baseline, weeks 1 2 4 and 6 post-exposure
- Needs to be sent to CDC via NML
References
- ^ Bart J. Currie, Linda Ward, Allen C. Cheng. David Joseph Diemert. The Epidemiology and Clinical Spectrum of Melioidosis: 540 Cases from the 20 Year Darwin Prospective Study. PLoS Neglected Tropical Diseases. 2010;4(11):e900. doi:10.1371/journal.pntd.0000900.
