What’s old is new again in bacterial control

Bacteriophages are finding more uses in food processing, but not yet in internal medicine

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A virus discovered a century ago could become a powerful weapon against disease and antimicrobial resistance in the livestock industry, according to an expert in the Canadian government.

Why it matters: Bacteriophages could be an antidote to antimicrobial resistance, which is undercutting options for antibiotics at a time when global demand for meat is rising.

Hany Anany.
photo: AAFC

“Phages are considered green, an environmentally friendly biocontrol approach that can be used to mitigate the risk of various bacterial pathogens,” says research scientist Hany Anany.

Anany has worked on bacteriophages (phages) for Agriculture and Agri-Food Canada since 2006.

Anany says that lytic phages are bacterial viruses that can only infect and multiply within their specific hosts, causing the bacterium to lyse (or disintegrate).

They have been studied extensively and, while most current applications are in the food processing sector, they have proven effective in controlling bacterial growth in food-producing animals.

Phages are used to control Salmonella, E. coli, Campylobacter, Clostridium and Listeria.

Phages were originally proven effective against bacterial infections in 1919 by Felix D’Herelle, a French-Canadian microbiologist.

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In fact, Anany says that D’Herelle’s first tests were with chickens to treat fowl typhoid.

With the discovery of antibiotics in 1934, this work was abandoned in western countries. Research into and the use of bacteriophages in human medicine continued in Eastern Europe and in Russia as a complement to antibiotics. Now, with concerns around antimicrobial resistance, phage therapy has regained currency.

“Phages are the most ubiquitous organisms on Earth and are also very common in foods,” Anany says. They also live inside humans and animals.

Their advantages are many, including the fact they target only specific bacteria, so no good bacteria are destroyed. They’re not toxic, can infect bacteria that are resistant to antimicrobials, don’t affect the taste, smell or appearance of foods and don’t alter the organic, halal or kosher designation of foods. They also usually don’t require repeat dosing.

So why haven’t they caught on in the livestock industry, where bacterial disease is the bane of farmers and their animals, and antimicrobial resistance is a danger? It’s partially because they are so specifically focused on destroying targeted pathogens.

“We don’t have a single phage to cover all E. coli serovars or Salmonella serovars,” Anany says, adding that using a cocktail of phages could be one answer, but it would be easier to tackle a less diverse strain such as Staphylococcus aureus.

They are also fussy about temperature, needing to be kept between 2 C and 8 C and can be rendered ineffective by disinfectants and sanitizers. There’s also the difficulty of obtaining wide consumer acceptance — phages are actually viruses and they’re added to food.

Anany cites a dearth of research in terms of veterinary use, pointing out that more needs to be done to validate phage treatment for animal bacterial diseases.

The effectiveness of phage treatment also varies according to the location and complexity of the infection — for example on skin, in the gastrointestinal tract, or in blood. He also says the regulatory barriers are very high for getting livestock treatments.

It’s also an expensive alternative, although Anany says that barrier will come down as more companies get involved in production.

“The human therapy area is more attractive to big pharma, especially with the recent successes of phage therapy in the U.S. and U.K.,” he says.

Phages are commercially available. Intralytix, a company in Baltimore, Maryland, makes and sells three products that target Listeria, Salmonella and E. coli in processed food. Micreos, a company based in The Netherlands, has similar products.

All these products are approved for use by the United States Department of Agriculture.

Health Canada actually has an entire list of antimicrobial food processing aids for use on red meats and poultry, including bacteriophages, for which it has “expressed no objection”.

In terms of livestock applications, Anany says he knows that Passport Food Safety Solutions, based in Des Moines, Iowa, makes a product called Finalyse, which is used as a pre-harvest wash on cattle hides to prevent E. coli. Intralytix also produces phage products that are effective on Salmonella and Clostridium in poultry.

Anany says more funded research is needed, particularly in large animal trials, and the government needs to support the industry in adopting more green antimicrobial approaches.

“It would be ideal if an integrated production system adopted phages throughout the chain,” he says. “For example, phages could be added to the feed and water for poultry on the farm, then sprayed on them before slaughter, then used during carcass processing and packaging – all the way from farm to retail.”

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