The Milk Producer - September 2011 - (Page 34)

APPLIEDSCIENCE By Céline Ster and François Malouin ith the goal of finding new ways to fight Staphylococcus aureus mastitis infections, an ambitious research program has developed a novel treatment approach. The result could be a new antibiotic on the market within a few years. Funded by the Canadian Bovine Mastitis Research Network, the research program was established to find bacterial genes expressed during intramammary infection. These genes are the tools the pathogen uses to cause an infection. We highlighted a certain number of those genes, including one in particular that could be targeted by a novel class of antibiotics. During our research program, dairy cows were infected with S. aureus. We collected milk samples, and analysed the genes expressed by S. aureus during the infection. During intramammary infection, S. aureus expresses the guaA gene, among others, which is vital to the bacterium’s survival. The gene leads to the production of guanosin monophosphate (GMP), which is the bacterium’s fuel. Controlling the guaA gene is a molecular switch called a riboswitch. It, in turn, is controlled by GMP. Following studies in collaboration with the laboratory led by Dr. Daniel Lafontaine at the University of Sherbrooke, we identified a molecule that resembles guanine and operates on the riboswitch in the same manner. This prototype molecule was called PC1. When we studied the growth of S. aureus in the lab, as shown in Figure 1, we found the switch opens when the bacterium needs fuel. GMP syn- A novel approach W Researchers come up with a new type of antibiotic to help ward off mastitis infections caused by S. aureus A cow is infused with a new antibiotic at the Sherbrooke research centre. thetase can be produced and, in turn, produce GMP fuel for the cell. When the cell has enough fuel, the surplus guanine binds to the riboswitch to close it, halting the production of GMP synthetase and GMP fuel. When the fuel level decreases again, a new cycle begins. This process takes place during an actual udder infection. The bacterium needs energy and GMP. To satisfy that need, the bacterium uses GuaA, and the riboswitch opens as shown in Figure 2. If we infused PC1 into the infected udder quarters, the molecule should bind to the switch and close it. This would block the GMP fuel production and cause the bacterium to die as shown in Figure 3. Bacteria numbers reduced We conducted trials to test the therapeutic potential of this novel class of 34 | September 2011 | MilkPRODUCER

Table of Contents for the Digital Edition of The Milk Producer - September 2011

The Milk Producer - September 2011
Contents
Editor’s Notes
DFO Chair’s Message
Dairy Update
Johne’s Update
DFC Promotion
Producer Profile
Cover Story
Research
Applied Science
Ruminations
Alternative Energy
Markets
New 'N' Noted
Back Forty

The Milk Producer - September 2011