Bacteria contaminations and food safety
When we talk about bacterial contaminations in food, this includes spoilage bacteria that results in undesirable organoleptic changes and deterioration, as well as pathogenic bacteria that causes foodborne diseases when in contact with the body through ingestion.3
Even with the worldwide standards related to microbiological safety in foods like regulation (CE) no. 2073/2005, contaminations occur; and foods such as poultry, milk, mushrooms, vegetables and fruits are related to outbreaks in the last years.4
There are five main bacteria responsible for most foodborne diseases: Salmonella, E. coli, Campylobacter, Listeria and Vibrio cholerae.1
Antimicrobials as a solution
Antimicrobials can be added to food processes, products and packaging to control and avoid these contaminations. Synthetic antimicrobials used in the food industry can cause undesired organoleptic changes and negatively affect foods with beneficial bacteria like cheese and yoghurt.5
Consumers worldwide are turning their preferences to more natural and organic foods with clean labels. They are becoming more conscious about what food they buy and want to avoid synthetic antimicrobials. This is one of the drivers for natural antibacterial agents as an alternative to synthetics – bacteriophages are revealing promising results as natural antimicrobials.6 Bacteriophages that target these specific bacteria responsible for food contamination can be used as antibacterial agents to avoid and control contaminations.
Bacteriophages
Bacteriophages, from the Greek meaning ‘bacteria eaters’, are viruses that kill specific bacteria and are the most abundant entities on Earth. Usually called phages, they are present everywhere in nature and control the bacteria in the environment.7
Phages were discovered in 1915 by Edward Twort who observed their bacterial activity, but it wasn’t until 1917 that Felix d’Herelle reported the use of phages to treat diseases (dysentery disease).8 Phage therapy is still used to successfully treat several bacterial diseases even today, so one may wonder why they are not more widely known or indeed used to treat diseases and bacterial contamination-related problems. When penicillin emerged on the scene as well as other antibiotics, phages started to be marginalised around the world, with the exception of some Eastern European countries.
How do phages work?
The way in which phages work is relatively simple; after binding to their correspondent and specific bacteria, phages use the protein machinery to replicate inside. This leads to the lysis of the bacteria and the release of newly formed phages, known as a lytic pathway. There is also the lysogenic pathway whereby phages input their genetic information into the bacteria chromosome without cell death. Due to safety reasons to ensure no genome change in the bacteria, phages with a lytic pathway are the ones that should be studied and used for food applications.9
Phages regulation
So, if phages are so good, why don’t we use them? In 2006, phages were allowed to be used as biocontrol agents by the US Food and Drug Administration (FDA), but even today their use in food is still very restrictive. The legal restrictions are very limiting and outdated; in 2019 the European Court of Justice allowed the use of phages in ready-to-eat foods to prevent Listeria contaminations even though the legal framework is absent.10
Today, some phage products are already approved. PhageGuard Listex and PhageGuard S. and E. are used against Listeria monocytogenes, Salmonella and E. coli respectively, for example. While LMP102 is used against Listeria monocytogenes in poultry packaging and ready‑to‑eat meat products.
Due to this interest in phages as a solution for food safety issues, we have seen novel applications in which phages are incorporated in a hope to improve phage stability and viability and allow the phage’s controlled release into the food product or packaging.
Phages and food industry
Due to the unique properties of phages, including their high specificity, low cost, maintenance of organoleptic properties and harmless properties, phages can be used to control foodborne diseases and food wastage.9 One third of all the food produced in the world is wasted, leading to big economic losses estimated at €143 billion per year in Europe; with people at risk of starving and malnutrition increasing at an alarming rate, change is desperately needed.11
Moreover, every year almost half a million people die because of foodborne diseases and almost 500 million people stay ill.1 A possible solution for this huge problem of food safety and wastage is the use of phages.
You will have probably heard about bacteria resistance and super bacteria over the last few years too, and this has only further driven research into phages as a solution.
Phages and food applications research
There are already some studies about the application of phage systems in food applications that are showing promising results as natural antimicrobial solutions.
Some interesting studies have shown the potential to apply phages in food packaging using coatings or nanofibres. Costa et al.12 developed coatings and nanofibres incorporating Felix O1 phage against Salmonella Enteritidis, and the results demonstrated successful incorporation and activity of the phage and a promising solution to use in food packaging to control Salmonella contamination.
Research must increase regarding applications of phages and phage systems in food
Alves et al.13 have also studied the use of coatings to encapsulate cinnamaldehyde and EC4 and φ135 phages to fight against Salmonella Enteritidis and E. coli. The researchers studied their effect in chicken meat, observing a synergy between the phages and the cinnamaldehyde and an antibacterial effect showing to be a feasible application for chicken packaging.
In other research using φIBB-PF7A phages to prevent Pseudomonas fluorescens in poultry, Alves et al.14 observed antibacterial activity in chicken breasts.
Phage systems applied into fruits have also been studied; Amarillas et al.15 used chitosan to load phages against E. coli O157:H7 and applied it onto the surface of a tomato. The team realised that the bacterial growth was significantly reduced by 3 log after one week.
Vonasek et al.16 also used T7 phage using whey protein isolate and beeswax as a delivery system and applied it as a coating onto cucumbers, apples and tomatoes, observing an antibacterial effect against E. coli BL21 and an antimicrobial effect in cut apples of 2 log and approximately equal to 1.5 logs in tomatoes.
The future
Research must increase regarding applications of phages and phage systems in food, and the study of different systems and methods to produce these phage systems must be extended. It is important to make continuous inspections to avoid the possibility of bacterial resistance to phages. Food regulation must be improved urgently so these solutions can be used and applied in the real world to help the food industry. The communication between science, food companies and consumers must be improved to allow a faster application of phage solutions and their acceptance and understanding.
If phages research related to food applications continues at this pace, in the next few years we will see solutions come to market that will help prevent food loss, foodborne diseases and death.
About the author
Maria Costa
Maria is a food scientist at CEB in University of Minho and at INL in Portugal. She graduated in 2011 in Biological Engineering – Chemical and Food Technologies, and since 2012 has been researching food innovation, valorisation and safety. Maria is currently finishing her PhD project focused on the development of bio-based systems to incorporate bacteriophages in the food industry to control Salmonella contaminations.
References
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- López-Cuevas O, Medrano-Félix JA, Castro-Del Campo N, Chaidez C. Bacteriophage applications for fresh produce food safety. Int. J. Environ. Health Res. 2019, 00, 1–16, doi:10.1080/09603123.2019.1680819.
- What are spoilage bacteria? Available online: https://ask.usda.gov/s/article/What-are-spoilage-bacteria (accessed on Aug 31, 2021).
- Public Health Advisories from Investigations of Foodborne Illness Outbreaks | FDA Available online: https://www.fda.gov/food/outbreaks-foodborne-illness/public‑health-advisories-investigations-foodborne-illness-outbreaks (accessed on Aug 31, 2021).
- Leung V, Szewczyk A, Chau J, et al. Long-Term Preservation of Bacteriophage Antimicrobials Using Sugar Glasses. 2017, doi:10.1021/acsbiomaterials.7b00468.
- Scott SE, Rozin P, Small DA. More for Preventatives Than for Curatives. J. Consum. Res. 2020, 1–57.
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- Pinto G, Almeida C, Azeredo J. Bacteriophages to control Shiga toxin-producing E. coli–safety and regulatory challenges. Crit. Rev. Biotechnol. 2020, 0, 1–17, doi:10.1080/07388551.2020.1805719.
- Sillankorva SM, Oliveira H, Azeredo J. Bacteriophages and their role in food safety. Int. J. Microbiol. 2012, 2012, doi:10.1155/2012/863945.
- Fernández L, Gutiérrez D, Rodríguez A, García P. Application of bacteriophages in the agro-food sector: A long way toward approval. Front. Cell. Infect. Microbiol. 2018, 8, 1–5, doi:10.3389/fcimb.2018.00296.
- Food Waste. Available online: https://ec.europa.eu/food/safety/food-waste_en (accessed on Aug 31, 2021).
- Costa MJ, Pastrana LM, Teixeira JA, et al. Characterization of PHBV films loaded with FO1 bacteriophage using polyvinyl alcohol-based nanofibers and coatings: A comparative study. Innov. Food Sci. Emerg. Technol. 2021, 69, doi:10.1016/j.ifset.2021.102646.
- Alves D, Cerqueira MA, Pastrana LM, Sillankorva S. Entrapment of a phage cocktail and cinnamaldehyde on sodium alginate emulsion-based films to fight food contamination by Escherichia coli and Salmonella Enteritidis. Food Res. Int. 2020, 128, 108791, doi:10.1016/j.foodres.2019.108791.
- Alves D, Marques A, Milho C, et al. Bacteriophage ϕIBB-PF7A loaded on sodium alginate-based films to prevent microbial meat spoilage. Int. J. Food Microbiol. 2019, 291, 121–127, doi:10.1016/j.ijfoodmicro.2018.11.026.
- Amarillas L, Ana LL, Heredia KAJB, León-félix AGJ. The antibacterial effect of chitosan-based edible coating incorporated with a lytic bacteriophage against Escherichia coli O157 : H7 on the surface of tomatoes. 2018, 1–10, doi:10.1111/jfs.12571.
- Vonasek EL, Choi AH, Jr JS, Nitin N. Incorporating Phage Therapy into WPI Dip Coatings for Applications on Fresh Whole and Cut Fruit and Vegetable Surfaces. 2013, 1–9, doi:10.1111/1750-3841.14188.
