Fighting Germs … With Viruses

Solutions to the increasingly dire public health threat of antibiotic resistance—as well as an agricultural illness that spoils $2 billion of milk every year—could come from the same much-maligned source: viruses.

Although we generally associate them with cold and flu season, a special type of virus known as “bacteriophage” can help protect us by killing disease-causing bacteria. Benefits of this approach include reduced reliance on antibiotics, which are losing their potency because of global overuse. This in turn could shrink the direct risks and costs of antibiotic use.

Daniel Nelson, associate professor of veterinary medicine and a fellow of the Institute for Bioscience and Biotechnology Research (IBBR), and Kasey Moyes, an assistant professor of animal and avian sciences, have teamed up to deploy bacteriophage enzymes called endolysins—a specialty of Nelson’s lab—to treat bovine mastitis, a common infection in dairy cows that renders vast quantities of milk unfit for consumption.

The U.S. Department of Agriculture recently awarded Moyes and Nelson $500,000 over three years to explore the use of one of these enzymes, PlyC, as a treatment that Nelson calls “enzybiotics” (a combination of “enzyme” and “antibiotics”), to kill the bovine mastitis-causing Streptococcus uberis bacteria.

“Essentially, endolysins break chemical ties in the bacterial wall, and the resulting high internal pressure within the bacterial cell causes it to explode and die,” Nelson said.

The Nelson Lab will scale up production to produce consistent, high-quality PlyC for this study and future applications. The lab will also study how PlyC works to kill S. uberis and how likely it is that bacterial populations will develop resistance to the new treatment. 

Moyes will assess the clinical effectiveness of PlyC in lactating dairy cows, both in treating and preventing S. uberis infection. Her group will also identify management and regulatory issues necessary for moving forward with PlyC as a new therapeutic.

“Beyond addressing the challenge of antibiotic resistance and reducing the rate of infection recurrence, PlyC is cleared by the system without any toxicity or chemical residue that may harm the animal as well as humans via consumption,” she said. “This would allow it to be implemented by both conventional and organic dairy producers.”