Campden BRI: Bacteriophage treatments are not a ‘magic bullet’

Bacteriophages are viruses (naturally present in the environment) that can kill specific host bacteria.

There are none approved at European-wide level, although some EU countries allow use under national rules.

The project focused on Salmonella spp., Campylobacter spp., Listeria monocytogenes, shiga toxin producing E. coli (STEC) and Staphylococcus aureus and was in response to a call by the UK Food Standards Agency (FSA).

It critically reviewed information on the use of bacteriophages on food to determine where and how they could potentially be used in food production.

It noted none of the studies had evaluated the use of phage in the field either in pilot facilities or in the factory environment.

Use to date​

From the evidence to date, suggested use would be as a processing aid to reduce the level of microorganisms at a set time point, said Campden BRI.

Generally Regarded As Safe (GRAS) approved, commercially produced bacteriophage are being used as food additives in the US and as processing aids in parts of Europe. 

They are being used to reduce the pathogen load of L. monocytogenes, Salmonella enterica and E. coli O157:H7 on poultry, red meat, RTE foods, fish, shellfish as well as processed fruits and vegetables.

Specific bacteriophages to reduce Listeria are permitted in Canada, Australia and New Zealand.

The major use of commercially produced bacteriophage to date is in the pre-harvest control of foodborne pathogens including STEC and Salmonella.

Although bacteriophages are being approved for use, one of the main barriers to wider use is the formulation of guidelines for safe and effective use. 

Three key safety concerns are: toxicological safety; emergence of resistance to biocides and antimicrobials linked to its use and the risk of release of bacteriophage into the environment.

Knowledge can be shared with the pharmaceutical sector, which has expertise in the use of bacteriophage to control microbial populations.

There are no specific controls to use of the treatments on foods but there are several regulations that must be complied with when using bacteriophage treatments in/on food products across Europe.

Food additive or processing aid?​

Efficacy of the bacteriophage is governed by its specificity; the potential for bacteriophage resistant mutants to be generated and the capability to protect the food product over life.

“There is insufficient data at present to support the use of bacteriophage to control the microbial load over product life and further work is needed to confirm if bacteriophage provide a one off ‘kill’ or are able to inactivate contaminating organisms introduced after the treatment period.​

“If bacteriophages have an ongoing effect and continue to reduce the level of bacterial contamination of food they would be regarded as food additives, which require approval prior to use under EU food additives legislation.  ​

“If they act as a one off ‘kill’ they may be considered to be processing aids and so would only require approval under EU food hygiene legislation if used to decontaminate the surfaces of meat or fish.”​

It is recommended that lytic bacteriophage should be used in preference to lysogenic bacteriophage as results suggest they are more effective.

Lysogenic bacteriophage fuses their genetic material into the host bacterial cell during infection while a lytic bacteriophage produces factors that break down the bacterial cell leading to cell death.

It is unlikely that a single bacteriophage would be effective against all strains of a particular bacterial species so a ‘cocktail’ may be necessary to reduce bacteria levels. 

Use with other antimicrobial treatments (e.g. nisin) often resulted in an improved ‘kill’ of target bacteria.

Knowledge gaps remain in the effectiveness of using bacteriophages against food spoilage bacteria due to a lack of published studies, the impact on toxin-producing bacteria and on how they influence the human gut microflora.