Burkholderia pseudomallei

Burkholderia pseudomallei (melioidosis)

Microbiology

• Oxidase positive, indole-negative Gram-negative rod with "safety pin" appearance
• Non-hemolytic

Epidemiology

• Humans and animals
• Important cause of death in SE Asia and northern Australia
  • Up to 80% seroprevalence in Thailand, mostly asymptomatic
  • Sporadic cases elsewhere
• 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 Presentation

• 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 shock
  • Pneumonia (50%)
  • GU infection (15%)
  • Skin (15%)
  • Primary bacteremia (10%)
  • Septic arthritis/OM (3-5%)
  • Neuro (3-5%)
• About 20% of clinical cases with develop septic shock

Diagnosis

• Culture

  • Blood, throat, and urine cultures 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
  • 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 is not reliable for identifying it

• Other methods

  • PCR
  • Immunofluorescence and latex agglutination
  • Serology (acute/convalescent)

  Management

  • Intrinsic resistance to many antibiotics, especially using efflux pumps
  • Ceftazidime
  • Amoxicillin-clavulanic acid
  • TMP-SMX

  Biosafety

  • Lab workers can have aerosol exposure
  • May need prophylaxis in high-risk patients
    • Septra or doxy or amox/clav
  • Monitor with serology at baseline, weeks 1 2 4 and 6 post-exposure
    • Needs to be sent to CDC via NML