University of Vermont

Research at The University of Vermont

Putting Vermont Farms to the Test


Stacked 15 high, 1,500 culture plates line the bench of John Barlow's lab at UVM. This is the collection of just one day at one Vermont farmstead cheesemaker's farm. Barlow's large-scale, entire-farm sampling hopes to come up with some novel pathogen-detection technology that may be particularly useful to small-scale, on-farm cheesemakers. His research on various forms of Staphylococcus will fill in the gaps in food safety professionals' knowledge: which agents are beneficial in the culturing of cheese, and which may affect human health.

The UVM animal scientist's epidemiology research addresses on-farm practices and milk quality using molecular biology to identify pathogens that influence milk quality. Building on the research of UVM listeria expert Catherine Donnelly, Ph.D., on how the safety of raw-milk cheeses informs national policy, Barlow's work is year two of a three-year $300,000 transdisciplinary grant from the USDA National Institute of Food and Agriculture.

On each of up to five Vermont farms that make artisan cheeses, Barlow and his team take milk samples from the mammary glands of all the cows in the herd, swabs of 15 different skin sites from six of the cows, and 15 different environmental samples from walls and stanchions. "This results in running about 1,500 culture plates per farm," says Barlow of the project whose goal is to collect from five artisan cheese-producing farms. "From this we typically select about 300 Staphylococcus species bacterial isolates for identification and molecular typing."

Back in the Barlow lab, Robert Mugabi, a second-year doctoral student, examines these for potential virulence characteristics such as the ability to form biofilms and antibiotic resistance genes. "We are doing a comprehensive survey to look for sources of Staphylococcus aureus and Staphylococcus species," Barlow explains. "The former is a food safety pathogen of concern, but other species appear to be important for the cheesemaking process and may play a beneficial role as important normal bacterial flora on the cow skin." To further complicate matters, some Staphylococci carry antibiotic resistant genes that could affect human health, which may act as a reservoir for antibiotic-resistance on dairy farms.

While it is too early to make conclusions, by using molecular typing techniques Barlow and colleagues are making progress in understanding the source of the sporadic new infections in these herds, which generally have a low prevalence of udder infections caused by this pathogen.

"Molecular typing has revealed some novel strains," Mugabi says. "However, there is still a lot to discover that could be important in answering some critical questions in animal health, food safety and public health."

Barlow continues to collaborate with Donnelly, and UVM researchers in community development and applied economics, David Conner, Ph.D., and Sarah Heiss, Ph.D., are also making major contributions to the social science aspects of the project. "We are proud of the transdisciplinary approach to this project," says Barlow. He and Donnelly are particularly excited about the opportunity to collaborate with Conner and Heiss as they work to understand how the public views artisan cheese farms and raw milk, and how social networks may influence perceptions of food safety.

"In the big picture, we are here to help artisan cheese producers improve animal health, milk quality and food safety," Barlow says, "and also to help these producers understand how consumers perceive these attributes for Vermont farms and how this affects their perception of food safety risk and ultimately their purchasing decisions."

Last modified May 26 2015 11:05 AM