Novel Antimicrobials Protect Against Mastitis-Causing Bacteria

An Agricultural Research Service (ARS)-led team has combined specific DNA segments from two different sources to produce a novel antimicrobial protein. The resulting "fusion" antimicrobial protein degrades the cell walls of several bacterial pathogens in a solution of whey extracted from cow's milk.

Agriculturally, the technology provides a key step to developing dairy cows that have a natural, built-in defense against mastitis—a disease that costs U.S. dairy producers up to $2 billion annually.

In the realm of infectious disease, one way to reduce microbial resistance that results from widespread antibiotic use is to come up with new ways to fight pathogens. The findings from this experimental study were published in the April 2006 issue of Applied Environmental Microbiology.

David M. Donovan, a molecular biologist at the ARS Biotechnology and Germplasm Laboratory at Beltsville, Md., presented the study's results today at the American Society for Microbiology's 2006 annual meeting, in Orlando, Fla. ARS is the U.S. Department of Agriculture's chief scientific research agency.

Donovan is the named inventor on a USDA/ARS-filed patent application that describes the technology behind fusing the protein-coding DNA sequences that produce the novel fusion antimicrobial. He and colleagues from Birmingham, Ala., and Quebec, Canada, hope to use the technology to produce fusion proteins as alternatives to the use of broad-range antibiotics both in clinics and on farms.

While all milk contains several naturally occurring antimicrobial proteins, such as lysozyme and lactoferrin, the sale of milk containing the fusion protein would first require rigorous food safety testing and federal regulatory approval.

Bacteria have layers of macromolecules that provide strength and shape to their cell walls. The fusion antimicrobial protein, as a cell-wall-degrading enzyme, kills pathogens by decomposing this structural layer and causing the cell to break down.

The B30-lysostaphin fusion protein developed by Donovan's team is active against both Staphylococcus aureus and three streptococcal mastitis pathogens that together are responsible for up to 50 percent of the dairy cattle mastitis that occurs in the United States.