Phages gain traction as food safety tools
August 3, 2010
by Steve Bjerklie
According to legend and tradition, a wade into the River Ganges or a dip into the waters at Lourdes will cure the sick and infirm, especially those suffering from infectious diseases such as leprosy and cholera. But, in fact, there’s some truth in the story – and the reason why may become one of the most important food-safety tools for meat packers and processors.
Certain waters contain a super-abundance of phages, viruses that are the natural enemies of bacteria. Indeed, phages, which were formally called bacteriophages, are thought to be the most-widely distributed and diverse organisms in the entire biosphere, according to the book “Bacteriophage: Genetics and Molecular Biology,” edited by McGrath and van Sinderen, and the study of phages has helped scientists understand the basic building blocks of life. They’re found everywhere, from the human gut to sea water – in short, where there are bacteria, there are phages.
“The collective biomass of phages is more than the collective biomass of all humans put together,” said Dirk de Meester, director of business development at EBI Food Safety in the Netherlands. “They’re the most omnipresent organism on the planet. Their estimated number is 10 to the 32nd power, an incomprehensible amount.”
What phages mean for meat packers and processors, he observes, is a simple fact: They “harness the power of nature to get rid of what you don’t want.” The ‘Borg’
The discovery of phages occurred about the same time as the discovery of antibiotics, but due to some poorly performed phage experiments, Western medicine generally came to favor antibiotics as an infectious disease therapy, though phages were commonly used medicinally in the former Soviet Union and still in present-day Russia. Phages are vicious attackers of bacteria: lytic cycle phages break open and destroy cells to replicate the phage virus, which then hunts down new hosts; lysogenic cycle phages merge with a host cell’s DNA to replicate, a kind of microscopic “Borg.”
Though knowledge of phages goes back more than 100 years to early research conducted at the Pasteur Institute in Paris, the Brown Institution in London and elsewhere – Sinclair Lewis’s 1926 novel “Arrowsmith” mentions phages as a therapeutic agent – the use of phages as a food-safety tool has come entirely in the 21st century. The Food and Drug Administration first approved use of phages in a food application in the U.S. in 2006 to control Listeria monocytogenes
in cheese. The following year, the F.D.A. broadened the approval to include all FDA-regulated foods.
The U.S.D.A. has followed suit, and two phages currently on the market, EBI’s Listex (distributed in the U.S. by World Technology Ingredients, or WTI) and Elanco Food Solutions’s Finalyse, are both approved for meat applications. Both products have limited application – but that’s their benefit. Phages are developed to destroy specific types and strains of bacteria: Listex targets Listeria
and Finalyse, which is a pre-harvest tool, targets E. coli
O157:H7 on cattle hides. Pre-harvest, post-processing
“We think phages are the most elegant way to control pathogenic bacteria,” commented Mr. de Meester. “It’s using the system nature has already developed to control bacteria, which would go wild if there weren’t phages. Really, all we are doing is taking this natural tool and directing its energy toward a specific pathogen that’s been a problem in foods. Listex targets Listeria specifically, and generally likes similar conditions.”
Elanco’s Dr. Patrick Mies, the company’s beef technical consultant for food safety, describes use of phages as a “novel” food-safety intervention, meaning it’s different from any kind of food-safety tool seen or used before. He emphasizes, however, that Finalyse is but one tool in a food-safety toolbox that packers should be taking advantage of. “Since there is no single food-safety intervention that acts as a ‘silver bullet,’ a pre-harvest intervention such as Finalyse enables post-harvest interventions to work more effectively,” he said.
For example, Finalyse used in conjunction with Elanco’s BoviBrom carcass wash, will provide a 2.5-3.5 log reduction in E. coli
numbers, according to the company. “The entire beef chain has been very focused on — and has invested heavily in — pre-harvest, food-safety interventions, and Finalyse is the first hide wash for live cattle that reduces the level of food-borne pathogens at the processing facility,” he added.
Dr. Aimee Belanger, a senior scientist for food safety at Elanco, noted that any single kind of phage targeting E. coli
O157:H7 may not be active against all strains of the organism that are found on cattle hides, so “Finalyse contains a mixture of phages that, when combined, are effective against nearly all of the E. coli
O157:H7 strains found on beef cattle,” she said.
EBI’s Listex is designed for in-plant topical treatment on processed products – on frankfurters emerging from the peeler, for example. “It really protects the entire exposed process,” said Mr. de Meester. Processors can expect a 1-3 log kill – “and as far as Listeria monocytogenes is concerned, that’s enough.” The potent product is added in tiny amounts, no more than 0.006 parts per million. Mr. De Meester said Listex adds no organoleptic qualities or off-flavors and will not reduce processed meat quality. Like Mr. Mies and Ms. Belanger, he emphasized the need to combine a phage tool with other food-safety tools. “The starting point has to be a clean plant. No intervention gives an excuse to work dirty, nor does the specific targeting of Listeria allow for this.”
Could the phages get loose and run wild in meat operations that, unlike packinghouses, actually want bacteria to be present – processors of fermented salami, for example? No, because phages are absolutely species-specific. The only phages a bacteria-using processor would need to worry about are naturally occurring phages that attack specific beneficial bacteria, and even if such phages colonized a processing plant, it’s easy to replenish the supply of beneficial bacteria from industry sources. Industry acceptance
Acceptance of phages in the packing and processing industry so far has been slow but steady. “Let’s face it, meat processors are a traditional market. They need to see the proof that something’s effective before they go all in,” said Mr. de Meester. “But in our experience, the more people know about phages, the cooler phages seem. They’re such an elegant food-safety tool.”
Mr. Mies and Ms. Belanger report that Finalyse, which was introduced to the market last year, has been well received by cattlemen and packinghouse yard personnel. Already, about one in four head of cattle processed in the U.S. are treated with Finalyse. The next step for the company is a Salmonella
-specific phage for poultry growers and processors. Steve Bjerklie is M&P’s East Coast correspondent based in Franconia, N.H. He has worked as a journalist covering the meat and poultry processing industry for more than 25 years.