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)
| Oxidase |
spp |
| + |
pseudomallei |
| - |
B.mallei, gladioli |
| V |
B.cepacia complex |
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 Dermnet 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)
