The incidence of Methicillin-Resistant Staphylococcus aureus in milk samples of Canadian dairy cows

Abstract

Mastitis is the most important disease in the dairy industry. In Canada, 10.3% of the clinical mastitis cases is caused by Staphylococcus aureus. More than 10% of them were found to be resistant to penicillin. Methicillin-resistant S. aureus (MRSA) contains the Mec-A gene, which makes the bacteria resistant to all β-lactam antibiotics. More and more MRSA infections and carriers are part of a community-associated strain, where originally most of them were healthcare-associated. Animals, farms and farmers seem to be a source, and are therefore a possible risk for public health. Worldwide, MRSA was found in pigs, horses, pets, cattle, chickens and sheep. In Canada it has been reported in pigs, horses, dogs, cats, but not in dairy cows. The first report of MRSA in dairy cattle was in Belgium, in 1975. More recently, researchers reported MSRA in dairy cattle in Italy (2006) and in Korea and Hungary (2007). In this study, milk samples were collected from about 80 farms all over Canada for two years. Approximately 2000 randomly collected S. aureus samples will be analyzed for MRSA. 550 samples are now done, all of them were not methicillin-resistant.