Phage product found effective against Listeria

To food pathogens like Listeria, bacteriophages are the viral hit squads of the microscopicworld. Bacteriophages are viruses that target bacteria, rather than human, plant or animalcells. For every bacteria, there is a phage that likes to latch on to them, take over their lifeprocesses and multiply. The baby phages then burst out to attack other nearby targets, thus killingthe host cell.

They have the potential to be the next big technological advance in anti-bacterial agentsprocessors can use in ensuring their products do not leave the plant loaded with dangerous pathogenslike Listeria, Salmonella, Campylobacter and E. coli

The study was done by Lieve Vermeiren of Belgium-based Gent University's department of foodsafety and food quality. He studied EBI Food Safety's Listex P100 bacteriophage product on luncheon meatsthat were artificially contaminated with Listeria monocytogenes.

The bacterium regularly causes serious food poisoning. The concern for this pathogen results from its ability to cause listeriosis in humans, a condition known for its30 per cent mortality rate.

Listeria incidentally occurs in unprocessed foods and is particularly renowned for its capacity to grow and reproduce even at low temperatures, at high salt- and low pH-conditions and for its tendency to occupy niches in the infrastructure of food processing companies. Contamination of luncheon meats is particularly a concern during the production process, at the slicing and packaging stage of industrial production.

Listex 100 is a natural product, used as a processing aid. It can act upon a broad spectrum ofListeria strains, thereby reducing the chances of contamination.

Vermeiren used the P100 phage, a bacteriophage which only targets the listeria bacterium, and which is known for its broadhost-range. His in-vitro experiments showed this phage to be lytic against all tested L. monocytogenes isolates at a temperature of 7°C.

Experiments on cooked poultry and ham products showed that application of P100 results in a reduction of the artificially added L. monocytogenes by more than Log3.

"The study confirms the efficacy of the lytic P100 to control Listeria monocytogenes on meat products duringproduction," Vermeiren stated. "Since phages are harmless to humans, animals and the environment, they can be used as an alternative biological manner of protection againstListeria."

The new European regulation concerning microbiological criteria for foods, which came into effect in January this year, states that for ready-to-eat foods the number of L. monocytogenes cells at the moment of consumption must be less than 100 per gram product.

"Applying an adequate dose of P100 phages allows ready-to-eat meat producing companies to meet this newstandard," EBI stated in a press release.