[co-author: Gloria Malpass, Ph.D.]
Photo by Adrian Lange on Unsplash
Food poisoning is an experience that no one is likely to ever forget. Some of the common bacteria that cause foodborne illness include Listeria monocytogenes (L. monocytogenes), Salmonella (S. enterica), and Escherichia coli (E. coli). Through the Food Safety Modernization Act (FSMA), the U.S. Food and Drug Administration (FDA) is pursuing a comprehensive regulatory scheme that covers food production and preparation from farm to table. The basic premise of FSMA is to prevent the introduction and spread of harmful bacteria and viruses that can cause foodborne illness. FSMA focuses on sanitary conditions for farms, food manufacturing facilities, food processors and food handlers, all for the purpose of preventing contamination of the food supply by harmful bacteria and viruses.
However, some viruses are being deliberately introduced into various foods — not to make people sick, but to prevent the growth of harmful bacteria. Bacteriophages, also called phages, are viruses that infect and reproduce within bacteria and can kill harmful bacteria. Phages were discovered in 1915, and were studied as treatments for bacterial infections prior to the discovery of antibiotics in 1928.
Phages are the most numerous lifeform on earth (estimated at 1031), and are found everywhere bacteria exist. Phages enter their host cells by binding to specific receptors — meaning that a specific type of phage can only infect specific types of bacteria. Once the phage infects the bacterium it can either replicate and kill the cell or integrate its DNA into the host DNA and be passed on to descendants of that bacterium. However, phages do not infect and replicate in human cells. Phages outnumber our gut bacteria by a factor of 10 and are important for regulating populations of bacteria in our bodies.
You may not realize it, but you are probably already eating foods treated with phages. In 2006, the U.S. FDA approved PhageGuard LISTEXTM P100 to control L. monocytogenes growth in cheeses. [GRN 198] LISTEXTM contained only one type of phage — P100. In 2007, the approval was extended to foods in general. [GRN 218] In 2014, the FDA cleared ListShieldTM, which is a mixture of six different phages specific for L. monocytogenes. [21 CFR 172.785; GRN 528] Since then, the FDA has also cleared phage products against Salmonella spp., Shigella spp., and E. coli. The standard pathway for obtaining clearance for phage products used to treat post-harvest foods is through application for a Generally Recognized as Safe (GRAS) designation, due to the ubiquitous nature of phages and their longstanding presence in our food supply.
Phages are a more natural alternative to antibiotics, pesticides and fungicides which might otherwise be used to treat the animals and crops that we eat. Phages are not believed to present any harm to humans (in fact, they already exist in our gut). Moreover, phages do not impact the taste of the food. Phage products are used to treat a wide range of foods, including meats, poultry, milk, and fresh fruits and vegetables during food production and processing. Phages can be used to replace antibiotics and chemicals that would otherwise be needed to control harmful bacterial growth in animals and plants. Phages can be introduced to animals while they are being raised and to fruit and vegetables while they are being grown. Phages may also be used during harvesting and preparation to control bacteria, and even included on packaging. In addition, phages may be used to clean surfaces in food processing facilities.
No commercial phage products are currently available for use against Campylobacter, another bacterium that commonly causes foodborne illness. However, one may soon be available. The Campylobacter-Specific Nullification via Innovative Phage-mediated Enteropathogen Reduction (C-SNIPER) project led by the Spanish technology center, AZTI, has developed a prototype phage product targeting Campylobacter and aims to have a commercial product available for use in poultry production and processing worldwide within the next two years. When this new product becomes available, approval by the FDA will be required for its use in food production and processing in the U.S. If approved, it will join the arsenal of other phage products already being used to kill harmful bacteria in our food.
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