DNase Agar

DNase Agar

SKU: KM0053 Category:

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.


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Product Description

Organisms Ref. No Result
Staphylococcus aureus NCTC 12981 Growth, white colonies and clear zones surrounding colonies *
Staphylococcus epidermidis NCTC 13360 Growth, white colonies and no clear zones surrounding colonies *
 *Following the addition of 1M hydrochloric acid



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


Suspend 41.3g of the medium in one litre of deionised / purified water. Allow the medium to soak whilst mixing for 10 minutes. Heat with frequent agitation and boil for one minute to completely dissolve the medium. Sterilise at 121°C for 15 minutes. Cool to 45-50°C and aseptically dispense into appropriate sterile containers.