Burkholderia pseudomallei

Burkholderia pseudomallei is a Gram-negative, bipolar, aerobic, motile rod-shaped bacterium. It causes the disease melioidosis in humans and animals and is also capable of infecting plants. The bacteria can from in a number of artificial environments.

Optimal temperature is around 40°C in pH-neutral or slightly acidic environments. Most strains can ferment sugars without gas formation. The bacteria produces both exo and endo toxins although the role of these toxins has not been fully elucidated.

It grows on a large variety of culture media. Colonies have a wrinkled, metallic appearance and possess an earthy odor. The organisms appear highly resistant on sensitivity tests.

Lab identification of B. pseudomallei is difficult in Western countries since it is rarely seen. They are often discarded as being of no clinical significance. Routine biochemical methods for identifying the bacteria vary widely in their identification of the organism. One differentiating factor is the organism’s resistance to antimicrobials which helps in identifying it. Most B. pseudomallei are instrinsically resistant to all aminoglycosides. Thailand commonly employs latex agglutination assay to identify the bacteria.
B. pseudomallei is susceptible to many disinfectants, heat above 74°C for 10 minutes, or UV irradiation. In humans it is called melioidosis which comes with a mortality rate of 20 to 50% even with treatment.

Ceftazidime is the antibiotic of choice. It is resistance to gentamicin and to colistin. It doesn’t have to pass through an animal host in order to replicate. It is one of the first proteobacteria to be identified as containing an active Type 6 secretion system. It also has a high mutation rate and it continues to evolve even after infecting the host.

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