AN ATYPICAL STAPHYLOCOCCUS-AUREUS INTRAMAMMARY INFECTION IN A DAIRY-HERD

An atypical Staphylococcus aureus (S. aureus) strain, isolated in a da iry herd over an 8 month period, was examined. The S. aureus strain wa s clumping factor negative, weakly heat-resistant deoxyribonuclease po sitive and produced narrow zones of double haemolysis. In total, 57 qu arter infections were observed. Prevalence data per month, calculated as the percentage of quarters infected with this atypical S. aureus st rain varied from 7.5% to 11.7% and the new infection rate varied from 0.14 to 0.55. In routine bacteriology, the large number of quarters in fected with the atypical S. aureus could easily be misclassified as qu arters infected with non-aureus staphylococci.