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Frequently Asked Questions

How are phages applied?

Phages can be applied of surfaces that could be inadvertently be contaminated by dipping or spraying of food products. They can also be applied in brines, batters and other liquids. Incorporating them into solid food matrices is not advisable as they would lose mobility.

How long do phages work?

Phage activity is short lived and as such they are considered processing aids. Phage activity on foods is limited to 24 hours but the majority of killing the target bacteria is observed within the first hour after application.

Are there considerations for factory workers or equipment?

Phages do not react with anything other than their host bacteria. They are odorless and tasteless and completely harmless to workers and equipment.

Does the use of phages result in resistant bacteria in the processing environment?

No, this does not happen. Phage pressure can result in the selection for mutant bacteria in a population but when treating food or food contact surfaces there is no phage pressure on the source of the contamination. Mutations occur randomly in a bacterial population. Phage resistant mutants do exist but if found on the treated foodstuff they would leave the processing environment with no feedback loop to their original source.

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What is the dose needed for killing bacteria?

Both bacteria and phages are incredibly small. To them the surface of foods is enormous, just as a country is enormous to hikers. Phages move only through passive diffusion and this motion is random. Therefore one needs a critical dose to ensure that rare bacterial contaminations and phages meet one another. For most foodstuffs 107 phages per cm2 results in a >1log kill.

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Under which conditions are phages functional?

Phages are stable and functional under almost all conditions encountered in food processing. They are functional within a wide range of pH and salt concentrations. They are however, very sensitive to denaturing and oxidizing chemicals such as hydrogen peroxide, chlorine, PAA and similar compounds. These substances react away quickly and phages can be applied after their use but combined use is not possible. Prolonged exposure to temperatures above 45°C should be avoided.

 

Will phages be effective on the problematic strain?

The phages in both PhageGuard Listex and PhageGuard S all have extremely broad host ranges. The phage in PhageGuard Listex infects all members of the Genus Listeria commonly associated with food processing facilities. The phages contained in PhageGuard S infect all serovars of Salmonella.