An agar diffusion method for the determination of antibodies against Staphylococcus aureus deoxyribonuclease.

On the addition of small concentrations of deoxyribonuclease, produced by Staphylococcus aureus, to Toluidine Blue DNA agar, a medium is produced on which antibodies against S. aureus deoxyribonuclease may be detected. When samples of milk, or blood serum, containing antibodies against S. aureus are applied into wells in the agar, the deoxyribonuclease activity is inhibited by the antibodies diffusing into the agar. As a result of this inhibition, blue zones are produced around the wells in the otherwise bluish-red agar. The diameters of the zones correspond to the concentrations of antibodies, and the method may consequently be used for qualitative and quantitative examinations of antibodies against S. aureus deoxyribonuclease in milk and serum. The procedure and certain limitations of the method are described.