Staphylococcus aureus (S. aureus) mastitis is extremely difficult to control by treatment alone. To date, successful control is gained only through prevention of new infections and culling of infected animals. S. aureus organisms colonize teat ends and/or teat lesions. Spread of infection can occur through milkers’ hands, washcloths, teat cup liners, and flies. During milking, irregular vacuum fluctuations can force bacteria up into the teat canal, leading to the potential for new infection. If not culled, infected cows must be segregated from the milking herd and milked last, or milked with separate milking units. A backflush system may help reduce bacterial numbers within the liners, but rinsing units by hand is certainly not recommended.