The Milk Producer - January 2010 - (Page 30)

APPLIEDSCIENCE By Jean-Philippe Roy, Marianne Allard, François Malouin and Julie Baillargeon Subduing S. aureus By identifying individual strains of these common bacteria, researchers aim at coming up with unique treatments For example, after diagnosing a new S. aureus infection in one of your cows, your veterinarian could tell you the identified strain does not respond to antibiotic treatment, has a strong potential for being contagious and causes chronic infections. You would probably cull this cow and not waste money on ineffective treatments. Your vet might also indentify a different strain that should respond well to antibiotic treatment, is not very contagious and does not increase SCC. The cow with this infection could be treated and stay in your herd. The bacteria express specific virulence genes. When combined with the infected cow’s immune system reactions, they determine the course of infection. Recently, we collected bacteria from several experimentally infected cows to study the virulence genes expressed by S. aureus during mastitis. Many of these genes caused cases of chronic mastitis, and represent new therapeutic targets for vaccine and antibiotic development. We are still not familiar with all the genes involved in virulence, but the research continues to shed light on the nature of S. aureus. These breakthroughs will soon prepare us to successfully fight it. Knowing which strain has infected a cow could help you determine whether to treat her. hanks to advanced laboratory techniques, dairy scientists now know there are different strains of the mastitis-causing bacteria Staphylococcus aureus. This knowledge forms the foundation of promising research aimed at finding solutions to better control S. aureus mastitis in your herd. S. aureus ranks among the most common causes of bovine mastitis. In a two-year survey of Canadian dairy farms, it was the most frequently identified bacterium in clinical mastitis cases. Most dairy herds in Canada and around the world experience significant economic losses from S. aureus. Losses are due to decreased milk production, antibiotic treatment costs 30 | January 2010 | MilkPRODUCER T for clinical mastitis and early culling of infected cows. The ability of S. aureus to cause intramammary infections provides an excellent example of a micro-organism adapting to its environment. The diagram on the opposite page shows how these bacteria infect a cow’s udder. Depending on the strain infecting a cow, S. aureus can increase somatic cell count (SCC), be highly contagious, exhibit antibiotics resistance, or cause chronic or clinical infections. Several possibilities arise from characterizing and identifying the virulence factors of each strain. They could include development of new vaccines, treatments and diagnostic tools. Jean-Philippe Roy is a veterinarian and assistant professor, faculty of veterinary medicine, Sherbrooke University, Marianne Allard is a doctoral student, Sherbrooke University, François Malouin is a professor, Sherbrooke University, and Julie Baillargeon is agronomist and transfer manager, Canadian Bovine Mastitis Research Network.

Table of Contents for the Digital Edition of The Milk Producer - January 2010

The Milk Producer - January 2010
Editor's Note
DFO Vice-Chair's Message
Contents
Dairy Update
Farm Finance
Processor Spotlight
DFC Promotion
Victory Over Johne’s
Applied Science
Research
Ruminations
Farm Energy
Markets
New 'N' Noted
Back Forty

The Milk Producer - January 2010