Overview of glucose nonfermenters

History

• Melioidosis was first described as a case series of 38 patients in Rangoon, Burma, by pathologist Alfred Whitmore in 1912 (hence the alternative name, ‘Whitmore’s disease’)

Taxonomy

• 79 Burkholderia spp.
• Non-cepacia complex spp:
  • gladioli (v nonpathogenic; may not cause disease in humans)
  • mallei (causes Glanders)
  • pseudomallei (causes Melioidosis)

Epidemiology

• Northern Australia
• SE Asia
• Other areas: Pacific, South Asia, Africa & Americas
  • • South Queensland, South USA recently confirmed
• Also seen in animals: pigs, cats, dogs, goats, sheep, horses, others
• Incidence: 165k/yr (approx 89k deaths) estimated

| Site | - Soil (10-90cm depth)

• ”Found in the rhizosphere around the roots of grasses, including rice, in the aerial portion of grasses, and in faeces of grazing livestock & native animals”
• Surface water
• Can be aerosolised during storms | | --- | --- | | Risk Factors | Diabetes (#1), liver disease, renal disease, EtOH XS, thalassemia, cancer, Non-HIV immunosuppression (esp. steroids), CF (Who are advised to avoid Melioid endemic areas)

No RF present in 16% (Aus) & 36% (Thailand) of cases

Indigenous Northern Australians SE Asian farm workers

Wet season | | Transmission | - Percutaneous/Inhalation/ingestion of contaminated soil/water

• Animal transmission (V rare; reported outbreaks in zoos/farms) | | Pathogenic mechanisms | Intracellular lifestyle —> immune evasion Replicates in both phagocytic & non-phagocytic cells Spreads cell-cell —> infected syncytia

Virulence factors

• 3 Type 3 secretion systems (T3SS): Deliver bacterial molecules into host cytoplasm
• T6SS x6: Intracellular survival
• BimA: Burkholderia intracellular motility A: actin polymerisation —> cell-to-cell spread
• Capsular polysaccharide
• LPS
• Flagella
• Burkholderia Lethal Factor 1 | | Clinical syndromes | Incubation: mean 9d, up to 21d (Range: 2d —> several years)

Latency

• Unknown prevalence
• ~3% conversion to active infection

Localised

• Australian children: skin lesion (see https://dermnetnz.org/topics/melioidosis for examples)
• SE Asian children: parotid lesions

Acute Melioidosis

• LRTI (50% on presentation)
• BSI (50% on presentation)
• 20% get septic shock
• Untreated mortality: 90%
• Can be complicated by…

Disseminated infection

• Organs involved typically include abscesses of the liver, lung, spleen, prostate
• uncommonly bone/joints, viscera, lymph nodes, skin, or brain.

Chronic

• 10% cases
• Sx lasting >2 months
• Typically ‘TB-like’ resp infection or non-healing skin infection | | Mortality | 10-40% |

Virulence factors (picture)