Measurement of Staphylococcus aureus nuclease and antinucleases. Applicability for the assessment of mastitic milk.

The concentration of the nuclease produced by Staphylococcus aureus and titres of antinucleases were determined in the udder secretions of 539 cows, most of them with clinical S. aureus mastitis. On average, the nuclease was detected in 85 % of the samples from mastitic quarters. In milk from most cows, antinucleases neutralize the activity of the nuclease, and a successful demonstration of this thermostable enzyme presupposed the inactivation of antibodies by heating the samples on boiling water-bath. The nuclease was demonstrated most frequently, and at highest concentration, in samples from cows with a severe mastitis and from cows which did not recover completely. The test for nuclease, performed out both non-heated and heated quarter samples, and the antimuclease test, may supplement conventional laboratory methods. The advantages and limitations of the methods in the diagnosis of mastitis are discussed.