Pseudomonas pseudomallei (aka Burkholderia pseudomallei) - MegaMicro

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Pseudomonas pseudomallei (aka Burkholderia pseudomallei)

Microbiology > Bacteriology > Gram-negative bacteria > Gram-negative bacilli > Pseudomonas
P. pseudomallei (also called Burkholderia pseudomallei)

a.       Structure
                          i.      Gram negative, rod-shaped, bipolar
                        ii.      Smooth form appears as long parallel bundles and rough form appears more irregularly arranged
                       iii.      Has two chromosomes (most bacteria have one!)
b.      Pathobiology:
                          i.      Oxidase-positive
                        ii.      Catalase-positive
                       iii.      Motile
                      iv.      Aerobic
                        v.      Non-spore forming
                      vi.      Saprophytic
                     vii.      Incubation time ranges from days to years
                   viii.      Grows best on pH neutral to slightly acidic
                      ix.      Virulence factors:
1.       Burkholderia lethal factor 1
2.       Capsular polysaccharide I
3.       Cluster I type VI secretion system
4.       Bsa type III secretion system
5.       Burkholderia intracellular motility factor A (BimA) – required for actin-based motility
6.       Filamentous hemagglutinin – helps adhere to host epithelial cells
c.       Epidemiology
                          i.      Soil-dwelling endemic in tropical and subtropical regions – particularly Southeast Asia (Thailand, Vietnam) and Northern Australia
                        ii.      Can infect both animals and humans through direct contact via inhalation, ingestion or open wounds

d.      Laboratory diagnosis
                          i.      Definite diagnosis can be made by culturing the organism from any sample, because the organism is never part of normal human flora .

e.      Disease manifestations
                          i.      Causes Melioidosis, also called Whitmore’s disease
1.       Melioidosis is associated with tropical climates (esp. Southeast Asia)
2.       Bacteria is found in contaminated water and soil
3.       Spread to humans and animals through direct contact with the contaminated source
4.       Symptoms are diverse – range from mild, localized skin infection to more severe, fatal presentations including septic shock, internal abscess and neurological involvement
5.       Commonly causes abscesses in the lung, bronchitis or pneumonia
6.       Patients typically present with fever and bloody sputum.
7.       Can also cause blood disease, kidney disease, heart disease, etc.
                     ii.         Diagnostic methods
1.       Diagnosed by isolating P. pseudomallei from the blood, urine, sputum, or skin lesions
2.       Also can be diagnosed by detecting and measuring antibodies to the bacteria in the blood
                    iii.         Differential diagnosis
1.       Clinically similar to Ganders disease – but the ecology and epidemiology are different
a.      Ganders is contracted by humans from infected domestic animals
b.      Glanders is caused by Burkholderia mallei
F. Therapy
1.       Treatment is divided into two stages:
a.       IV intensive phase – IV ceftazidime (cephalosporin, 3rd gen) or IV meropenem (β-lactam)
                     i.      Given for 10-14 days until the patient’s temp has returned to normal
b.      Eradication phase – treatment with co-trimoxazole (sulfonamide) and doxycycline (tetracycline) for 12-20 weeks to reduce recurrence
2.       Requires combination of antibiotics because the bacteria is resistant to most antibiotics – treatment usually lasts over a month
3.       Surgically drain any abscesses

E. Prevention and control
1.       Currently no vaccines available
2.       In endemic areas, avoid contact with soil, mud, and surface water
3.       Populations at risk are patients with diabetes mellitus, chronic renal failure, chronic lung disease, or immune deficiency of any kind
4.       Wear boots if possible
Related concepts
  1. Gram-negative bacteria
  2. Gram-negative bacilli
  3. Pseudomonas
  4. P. pseudomallei
  5. Tropical
  6. Melioidosis
  7. Soil
  8. Burkholderia pseudomallei

Web links:

1. Burkholderia pseudomallei Info (Missouri S&T Microbiology):
a. Useful for pictures
2. Melioidosis Info (CDC):
a. Very thorough source

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