Ashdown's medium

Ashdown's Medium

Ashdown's medium is a selective culture medium used primarily for the isolation and identification of Burkholderia pseudomallei, the bacterium responsible for melioidosis. This medium is named after Dr. L. R. Ashdown, who developed it in the 1970s to improve the detection of this pathogen in clinical specimens.

Composition

Ashdown's medium is a complex medium that contains the following components:

• Trypticase soy agar
• Glycerol
• Crystal violet
• Gentamicin

The medium is designed to inhibit the growth of most other bacteria while allowing Burkholderia pseudomallei to grow. The addition of glycerol enhances the growth of B. pseudomallei, while crystal violet and gentamicin suppress the growth of Gram-positive bacteria and other Gram-negative bacteria, respectively.

Uses

Ashdown's medium is primarily used in clinical microbiology laboratories for the isolation of Burkholderia pseudomallei from clinical specimens such as sputum, blood, and pus. It is particularly useful in regions where melioidosis is endemic, such as Southeast Asia and Northern Australia.

Procedure

To use Ashdown's medium, a clinical specimen is inoculated onto the surface of the agar. The plate is then incubated at 37°C for 48 to 72 hours. Colonies of Burkholderia pseudomallei typically appear as small, wrinkled, and purple due to the uptake of crystal violet.

Advantages

• Selective for Burkholderia pseudomallei
• Inhibits the growth of contaminating flora
• Enhances the detection of B. pseudomallei in mixed cultures

Limitations

• Requires specific incubation conditions
• May not completely inhibit all non-target organisms
• Not suitable for all types of specimens

Also see

• Burkholderia pseudomallei
• Melioidosis
• Selective media
• Microbiological culture