While statistical data from around the world is fragmented, there’s enough evidence to show a definite increase in the number of cases of listeriosis. An EU report shows a steady rise in reported listeriosis cases for Denmark, the UK, Germany, Spain, France and Finland, all of which are developed countries with rigorous food safety controls.
In the US, Centers for Disease Control and Prevention estimates that 2,500 people become seriously ill with listeriosis each year, and of these around 500 die.
The financial and ‘reputational’ risks to manufacturers in terms of product recall and human tragedy necessitate a fundamental approach to bacterial control: eradicate this pathogen before food hits the chill chain and the consumer’s table.
An effective answer to the control of listeria in dairy processing lies in using nature’s own weaponry, bacteriophages, which are antibacterial microorganisms. Phages are ubiquitous and are routinely consumed with all foodstuffs without any adverse impact on human health or enjoyment of food flavours.
While there has been extensive research into the use of phages in the food industry, harnessing their power for convenient and cost-effective use as a topical treatment has been a relatively recent achievement. To date, EBI Food Safety is the only company to have brought a bacteriophage product to market that provides consistent control of listeria, called Listex.
Phages come in many different varieties and are species-specific to bacteria. As soon as the target host cells have been eliminated, the phages have no further function, fulfilling their life cycle and dissolving into harmless amino acids, leaving behind no residue or ecological footprint.
Listex is a solution of listeria-specific phages, able to destroy the harmful target bacteria, even when the latter are present in low levels or hidden in hard-to-reach crevices. Application of Listex at critical production points significantly reduces the risk of subsequent outgrowth of listeria in later stages of the product’s life cycle.
Listex is approved as Gras (Generally Recognised as Safe) by the FDA and USDA/FSIS, and has been shown to be effective against all relevant listeria monocytogenes strains tested. Moreover, since it is of organic origin and doesn’t attack any of the beneficial bacteria so essential in cheesemaking, it’s being welcomed by many producers of fine quality and organic cheeses who are normally resistant to introducing processes that interfere with nature.
Organic and non-GMO accredited, Listex doesn’t affect the colour, taste, touch or smell of cheese in any way. It can be applied to a wide variety of cheeses during brining, washing, slicing or shredding. Used as a spray treatment to the surface of the cheese or added to the brine or smearing solution, it helps to prevent cross-contamination. It’s very important to treat white mould cheeses, such as Camembert and Brie, before the fungus develops.
Surface-smeared cheeses are especially vulnerable to listeria infection. Treatment is performed either by adding the phage culture to the smearing solution or spraying it directly onto the cheese surface, or using a combination of these methods. During ripening, a single remaining bacterium on one cheese can begin the recontamination process from this cheese to others, so it’s vital to continue treatment throughout the ripening process.
Initial contaminations of listeria during food production may be relatively low, but it’s subsequent outgrowth to dangerous levels that poses the greatest risk to consumers. This can happen if dairy products are eaten past their use-by date or stored in fridges that are too warm. As correct domestic fridge temperatures cannot be guaranteed, the Panel on Biological Hazard states that “temperature variability in the chill chain should be taken into account in both challenge tests and in the use of predictive models to establish the shelf life of foods”.
However, eradication or massive reductions of these initial low-level contaminations using bacteriophages during processing can also ensure that far fewer products leave the production facilities with even low levels of contamination. The risk of subsequent outgrowth to dangerous levels in a particular item is then much reduced.
By using bacteriophages as a regular part of their production routine, dairy processors can secure peace of mind as the phages kill the potentially deadly bacteria, rather than just inhibiting their growth. By applying a well formulated solution at the critical processing points, they can demonstrate that they have taken every care and due diligence to ensure that, on leaving the factory, their products are safe and free from listeria.
Steven Hagens is chief scientific officer at EBI Food Safety, a Dutch company that develops natural bacteriophage products against dangerous bacteria in food.
© FoodBev Media Ltd 2024