The Milk Producer - August 2010 - (Page 36)

APPLIEDSCIENCE By Julie Baillargeon, Marie-Ève Paradis and Daniel Scholl On-farm CSI Powerful new test using DNA to identify mastitis-causing bacteria could have a major impact on your management hen a crime is committed, investigators often determine the culprit’s identity through DNA traces left at the crime scene. Veterinarians and dairy producers could detect mastitis-causing bacteria in much the same way with powerful new tests especially designed to identify these pathogens in milk samples. The technique used to analyse bacteria DNA is the polymerase chain reaction (PCR). Some laboratories have been offering it as a mastitis diagnostic tool for a few years now, but available tests identify only one bacterium at a time, and are more expensive than traditional bacterial cultures. New tests on the market, called multiplex PCRs, can identify several pathogens at the same time. Most of them can even measure how many bacteria are in a sample, known as real-time PCR. These tests have proven highly effective in laboratories, offering a promising avenue for diagnosing mastitis. Still unknown, however, is their true sensitivity and specificity in the field. Sensitivity is the percentage For more information and practical udder health resources, visit www.mastitisnetwork.org and subscribe to our electronic newsletter, Mastitis-Flash. W of false negative test results and specificity the percentage of false positives. Dr. Daniel Scholl, scientific director of the Canadian Bovine Mastitis Research Network (CBMRN) and epidemiology professor in the University of Montreal’s faculty of veterinary medicine, decided to remedy this situation. He initiated a project to evaluate PCR testing accuracy by estimating sensitivity and specificity results. Both can significantly impact a dairy farm since a misdiagnosis could result in the wrong management decision. Scholl and his team are studying a large quantity of samples taken from the 91 herds in the CBMRN’s National Cohort of Dairy Farms, a representative cross-section of the Canadian dairy population. So, study results will apply directly to your farm. The study is checking sensitivity and specificity by using samples taken from cows showing clinical mastitis symptoms and lactating cows with no apparent symptoms. There is no ideal diagnostic method for detecting mastitis bacteria in milk. Bacterial cultures—normally used to analyse samples sent to the laboratory—still serve as the reference method or gold standard. Accordingly, all cohort samples first underwent a bacterial culture. The study is comparing these results with those of PCR analyses. Identifying the bacteria causing a mastitis case helps you determine the proper treatment. 36 | August 2010 | MilkPRODUCER http://www.mastitisnetwork.org

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

The Milk Producer - August 2010
Contents
Editor's Notes
DFOVice-Chair's Message
Dairy Update
Industry Roundup
DFC Promotion
Issues Update
Research
Applied Science
Ruminations
Markets
New 'N' Noted
Back Forty

The Milk Producer - August 2010