Burkholderia pseudomallei
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Burkholderia pseudomallei
Burkholderia pseudomallei (also known as Pseudomonas pseudomallei) is a Gram-negative, bipolar, aerobic, motile rod-shaped bacterium. It infects humans and animals and causes the disease melioidosis. It is also capable of infecting plants.
B. pseudomallei measures 2-5 μm in length and 0.4-0.8 μm in diameter and are capable of self-propulsion using flagellae. The bacteria can grow in a number of artificial nutrient environments, especially betaine- and arginine-containing.
in vitro, optimal proliferation temperature is reported around 40°C in pH-neutral or slightly acidic environments (pH 6.8–7.0). The majority of strains are capable of fermentation of sugars without gas formation (most importantly, glucose and galactose, older cultures are reported to also metabolize maltose and starch). Bacteria produce both exo- and endo-toxins. The role of the toxins identified in the process of melioidosis symptom development has not been fully elucidated.
| Kingdom | Bacteria |
|---|---|
| Phylum | Proteobacteria |
| Class | Betaproteobacteria |
| Order | Burkholderiales |
| Family | Burkholderiaceae |
| Genus | Burkholderia |
| Species | B. pseudomallei |
| Binomial | Burkholderia pseudomallei |
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[edit] Surface Characteristics
Polysaccharide capsule of B. pseudomallei plays a role in environmental protection, immune system evasion and attachment to epithelial cells
[edit] Pathogenic Activity
Burkholderia pseudomallei is a human and animal pathogen and is the cause of melioidosis, which is a disease native to Southeast Asia and northern Australia. It releases exo and endo toxins but their role in instigating the symptoms of melioidosis is not yet fully understood. Nevertheless, infection is spread through ingestion or contact of bacteria onto open skin wounds or through the inhalation of the aerosolized Burkholderia pseudomallei. Melioidosis can be classified as acute or chronic depending on the incubation time before symptoms appear. Burkholderia pseudomallei mimics tuberculosis in its ability o lay dormant without showing any symptoms for years. Common symptoms include fever, formation of abscess on various parts of the body such as the brain, osteomyelitis, bacteremia and various diseases of the heart, kidney and lungs such as pneumonia. Burkholderia pseudomallei is thought to have biological warfare potential and its virulence is made evident by being listed as a “Category B agent” by the US centers for Disease Control.
[edit] Virulence
B. pseudomallei is an "accidental pathogen". It is an environmental organism that has no requirement to pass through an animal host in order to replicate. From the point of view of the bacterium, human infection is an evolutionary "dead end".
Strains which cause disease in humans differ from those causing disease in other animals by possessing certain genomic islands.
B. pseudomallei is able to invade cells, polymerise actin and to spread from cell to cell, causing cell fusion and the formation of multinucleate giant cells.
B. pseudomallei is one of the first proteobacteria to be identified as containing an active Type 6 secretion system. it is also the single organism identified that probably contains up to 6 different independent type 6 secretion system.
It may have the ability to cause disease in humans because of DNA it has acquired from other microorganisms. The mutation rate is also high, and the organism continues to evolve even after infecting the host.
B. pseudomallei is intrinsically resistant to a large number of antimicrobial agents. One important mechanism is that it is able to pump drugs out of the cell, and this mediates resistance to aminoglycosides (AmrAB-OprA), tetracyclines, fluoroquinolones and macrolides (BpeAB-OprB).
