DNase Agar

DNase agar is used primarily in clinical laboratories to differentiate pathogenic Staphylococcus aureus from other staphylococci based on deoxyribonuclease (DNase) activity.

The tryptone provides the required carbon, nitrogen and vitamins. Sodium chloride maintains the osmotic balance. The addition of DNA to the base medium provides a simple method to check for DNase activity.

Following incubation of the inoculated medium, the surface of the medium is flooded with a small quantity of 1M hydrochloric acid to precipitate the DNA. This results in the medium turning opaque. Organisms that can produce sufficient quantity of a DNase enzyme will hydrolyse the DNA resulting in a clear area around the colonies. Whereas DNase negative organisms will not produce clearing.

NB: As with most tests of this type a positive result should not be taken in isolation and other appropriate tests, e.g. coagulase test, latex agglutination etc., should be carried out.

Additional Information

Shelf Life (days): 1095 days

Storage Temp (C): 10-30°C

Dehydrated Medium Appearance: Fine Powder

Prepared Medium Appearance: Firm Gel

Dehydrated Medium Colour: Beige

Prepared Medium Colour: Straw

Dehydrated PH: 7.3±0.2

Prepared PH: 7.3±0.2

Recommended Incubation: Aerobically at 35-37°C for 18-24 hours

Formula*g/L

Tryptone: 20.0

Deoxyribonucleic acid: 2.0

Sodium chloride: 5.0

Agar: 14.3

Total: 41.3

*Adjusted/supplemented as required to meet performance requirements