Brucella + Burkholderia
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.
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. 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).
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.