Burkholderia pseudomallei

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Burkholderia pseudomallei / (Redirected from Melioidosis)

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 shock12
    • 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

Prevention

Laboratory Safety

References

  1. ^  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.
  2. ^  E. M. Meumann, A. C. Cheng, L. Ward, B. J. Currie. Clinical Features and Epidemiology of Melioidosis Pneumonia: Results From a 21-Year Study and Review of the Literature. Clinical Infectious Diseases. 2011;54(3):362-369. doi:10.1093/cid/cir808.