Pathogenicity of different species of staphylococci in caprine udder

Aseptic foremilk samples were collected from Finnish landrace goats. Ten different species of staphylococci, causing subclinical infections were detected. Twelve goats with persistent subclinical staphylococcal infection were followed on a monthly basis and compared with foremilk samples of nine goats suffering from clinical mastitis. Parameters of inflammation based on the activity of the California Mastitis Test (CMT). N-acetyl-beta-D-glucosaminidase (NAGase) and antitrypsin were determined from the milk. Staphylococci were further classified using the API STAPH system. On the basis of elevations of activities of CMT, NAGase and antitrypsin, Staphylococcus aureus was the most pathogenic in clinical and subclinical mastitis, S. hyicus showed only marginal pathogenicity. Subclinical infections were persistent and the infective organism was not always detected from milk by culture. The biochemical reactions of subclinical staphylococci seemed to vary within the same gland by time. Antitrypsin was most effective in differentiating between subclinical and clinical infection. A teat cistern puncture technique was found to be suitable for the goat.