Burkholderia pseudomallei
| Burkholderia pseudomallei | |
|---|---|
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| B. pseudomallei colonies on Ashdown's agar showing the characteristic cornflower head morphology | |
| Scientific classification | |
| Kingdom: | Bacteria |
| Phylum: | Proteobacteria |
| Class: | Beta Proteobacteria |
| Order: | Burkholderiales |
| Family: | Burkholderiaceae |
| Genus: | Burkholderia |
| Species: | B. pseudomallei |
| Binomial name | |
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Burkholderia pseudomallei (Whitmore 1913) Yabuuchi et al. 1993 |
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| Synonyms | |
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Bacillus pseudomallei Whitmore 1913 |
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Bacillus pseudomallei Whitmore 1913
Bacterium whitmori Stanton and Fletcher 1921
Malleomyces pseudomallei Breed 1939
Loefflerella pseudomallei Brindle and Cowan 1951
Pfeiferella pseudomallei
Pseudomonas pseudomallei (Whitmore 1913) Haynes 1957
Burkholderia pseudomallei (also known as Pseudomonas pseudomallei) is a Gram-negative, bipolar, aerobic, motile rod-shaped bacterium. It is a soil-dwelling bacterium endemic in tropical and subtropical regions worldwide, particularly in Thailand and northern Australia. 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 is capable of self-propulsion using flagella. The bacteria can grow in a number of artificial nutrient environments, especially betaine- and arginine-containing ones.
In vitro, optimal proliferation temperature is reported around 40 °C in 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 endotoxins. The role of the toxins identified in the process of melioidosis symptom development has not been fully elucidated.
B. pseudomallei is not fastidious and grows on a large variety of culture media (blood agar, MacConkey agar, EMB, etc.). Ashdown's medium (or Burkholderia cepacia medium) may be used for selective isolation. Cultures typically become positive in 24 to 48 hours (this rapid growth rate differentiates the organism from B. mallei, which typically takes a minimum of 72 hours to grow). Colonies are wrinkled, have a metallic appearance, and possess an earthy odour. On Gram staining, the organism is a Gram-negative rod with a characteristic "safety pin" appearance (bipolar staining). On sensitivity testing, the organism appears highly resistant (it is innately resistant to a large number of antibiotics including colistin and gentamicin) and that again differentiates it from B. mallei, which is in contrast, exquisitely sensitive to a large number of antibiotics. For environmental specimens only, differentiation from the nonpathogenic B. thailandensis using an arabinose test is necessary (B. thailandensis is never isolated from clinical specimens). The laboratory identification of B. pseudomallei has been described in the literature.
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