Burkholderia pseudomallei

Background

Microbiology

• Oxidase-positive, indole-negative Gram-negative bacillus with "safety pin" appearance
• Non-hemolytic
• Colonies are dry and wrinkly

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