Got Milk? ARS Develops Test to Keep It Safe

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Dairy farmers were crying over spilled milk, 15 million tons of it. So Agricultural Research Service (ARS) immunochemist Larry Stanker decided to do something about it. Stanker invented a method of detecting the residue of a potent antibiotic given to dairy cattle and other farm animals, making testing methods more accurate and saving large quantities of milk from unnecessarily being discarded every year.

Stanker, a scientist with the Foodborne Contaminants Research Unit in Albany, California, developed an antibody that flags traces of ceftiofur, an antibiotic used to treat bacterial infections in dairy cattle, as well as respiratory diseases in cattle, horses and swine. In doing so, he solved a problem that had long bedeviled dairy farmers.

The Food and Drug Administration monitors the amount of antibiotic residue in animal food products, including milk, meat, poultry and eggs. Milk with ceftiofur residue is considered unsafe, and must be discarded. With prior tests, inspectors could not easily distinguish ceftiofur from other potentially less harmful antibiotic residues. As a result, whenever an antibiotic residue was detected, inspectors ordered the milk to be discarded, just to be safe. And because the inspectors did not know whether it was ceftiofur they had found, they couldn't work with the farmers to pinpoint and solve the problem.

The previous tests were also cumbersome, or used expensive equipment requiring highly trained personnel. The ARS antibody can accurately detect the presence of ceftiofur with a simple strip test, which is now commonly used in the field at farms to pre-screen raw milk before it is trucked, and at creameries.

The antibody was patented and licensed to a private company that produces detection kits about 10 years ago, and it is now one of the highest royalty revenue-generators in the ARS patent licensing program.

The ARS initiated a Material Transfer Agreement to transfer samples of the antibody to a commercial immunoassay kit manufacturer, Charm Sciences, Inc., of Lawrence, Massachusetts. Following extensive evaluation supported by Stanker, Charm obtained a license for commercial use of the antibody, and the ARS transferred the antibody cell line to the company. In 2009, the Neogen Corporation received a nonexclusive license to the technology in order to produce its own commercial testing kit.

In addition, Stanker collaborated with the Food Safety and Inspection Service to develop a simple assay that detects ceftiofur residues in bovine and porcine kidney, which is predictive of levels in muscle and meat.

Stanker's invention takes advantage of the recognition powers of antibodies. When there is an infection, the immune system makes antibodies that recognize and bind to foreign bodies. Stanker created an antibody that is specifically designed to bind with ceftiofur, though not with other antibiotic drugs, and so serves as a flag or marker for that antibiotic. That same concept, using the recognition abilities of antibodies, is used to detect other types of contaminants in food, and has a wide range of other uses, including the diagnosis of diseases.

Stanker has continued his research into the detection of small molecules using monoclonal antibodies. He is now developing novel immunoassays for detection of infectious prions and botulinum neurotoxin, and his research is increasingly attracting commercial interest.

The FLC Far West Region recognized Stanker with an Outstanding Commercialization Success Award for the development of the ceftiofur antibody.