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Brucella + Burkholderia
Brucella
Burkholderia pseudomallei is a Gram-negative, bipolar, aerobic, motile rod-shaped bacterium.[1] A human and animal pathogen, B. pseudomallei causes melioidosis.
B. pseudomallei measures 2–5 μm in length and 0.4–0.8μm in diameter and are capable self-propulsion using flagellae. The bacteria can grow in a number artficial 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 understood.[2]
Identification
B. pseudomallei grows on a large variety of culture media (blood agar, McConkey's, EMB, etc.). Ashdown's medium (or Burkholderia cepacia medium) may be used for selective isolation.[3] 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), and 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 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 non-pathogenic B. thailandensis using an arabinose test is necessary (B. thailandensis is never isolated from clinical specimens).[4]
Laboratory identification of B. pseudomallei can be difficult, especially in Western countries where B. pseudomallei is rarely seen. The large wrinkled colonies look like environmental contaminants and are therefore often discarded as being of no clinical significance. Even when the culture is recognised to be significant, commonly used identification systems may misidentify the organism as Chromobacterium violaceum or other non-fermenting gram-negative bacilli such as Burkholderia cepacia or Pseudomonas aeruginosa.[5][6] Again, because the disease is rarely seen in western countries, identification of the bacterium B. pseudomallei in cultures may not actually trigger alarm bells in physicians unfamiliar with the disease.[7]
Molecular methods (PCR) of diagnosis are possible, but not routinely available for clinical diagnosis.[8][9]
B. pseudomallei is the cause of melioidosis. There are number of different forms of melioidosis, but sepsis due to B. pseudomallei has a mortality rate of 80 percent if untreated.
Antigens
Antibodies
Antisera
Kits
Rapid Tests
QC Materials
