Bacteriophages: Fighting off disease-causing germs

Published: 30-01-2014

Bacteria eaters
Bacteriophages – Greek for “bacteria eaters” – were discovered nearly a century ago. Bacteriophages are viruses capable of infecting only bacteria and are among the most common microorganisms on earth. They are approximately 100 times smaller than a typical bacterium and they destroy bacteria in a process called lysis. They are present in significant numbers in soil, water, and foods of various origins. Moreover, bacteriophages are also present in the gastrointestinal tract of humans and animals. There are numerous types of bacteriophages known, each killing only their “own” type of bacterium. This means that bacteriophages are highly host-specific, exhibiting only narrow host ranges, usually targeting specific bacterial strains.

Bacteriophage therapy was established during the 1930s, for example, in France, the U.S. and in the Republic of Georgia. However, phage therapy and phage research was abandoned in most of the Western world, primarily due to the advent of antibiotics. More recently, the rise of antibiotic resistance has been responsible for the renewed interest in bacteriophages and their promising use in human and veterinary medicine, in agriculture and animal farming, and in the food industry.

Bacteriophage technology as a new industry standard
Micreos Food Safety develops antibacterial food safety solutions based on its bacteriophage technology. “Our company is committed to turning the application of bacteriophages into a new industry standard for the control of unwanted pathogens in food products,” CEO Mark Offerhaus says.  In 2006, LISTEX™ P100, Micreos Food Safety’s product against Listeria monocytogenes, was recognized as GRAS (Generally Recognized as Safe) by the U.S. FDA. LISTEX™ P100 is used as a processing aid in the production of meat, cheese, fish and other products and is aimed at prevention of the outgrowth of Listeria strains during food processing. In 2007, Micreos Food Safety was the winner of the Food Ingredients Europe Gold award for providing a new approach to an urgent and growing problem that affects both consumers and manufacturers. Since then, LISTEX™ has been approved by the Dutch Ministry of Health as a processing aid (July 2009) and earmarked as an organic (natural) product by SKAL/Dutch Ministry of Agriculture.

Listeria monocytogenes causes listeriosis, a serious infection that has recently been recognized as an important public health problem in the United States and in other countries. In the United States, an estimated 2,500 people become seriously ill with listeriosis each year, and around 500 of these die (source: CDC website). Scientists at the European Food Safety Authority have indicated that the risks in food from Listeria are on the increase (source: EFSA website). Healthy adults and children occasionally become infected with Listeria, but rarely become seriously ill. The disease primarily affects persons of advanced age, pregnant women, newborns, and adults with a weakened immune system. Infections during pregnancy can lead to miscarriage or stillbirth, premature delivery, or infection of the newborn. Listeria bacteria are ubiquitous in the environment; they are found in soil and water. Many animals carry the bacteria in their feces. Transmission generally occurs through the consumption of contaminated food. The bacterium has been found in a variety of raw foods, such as unpasteurized (raw) milk, uncooked meats and vegetables, as well as in processed foods that became contaminated after processing, such as soft cheeses and cold cuts at the deli counter. Listeria monocytogenes is destroyed by cooking, but can grow at refrigeration temperatures, in low oxygen environments, and at high salt concentrations.

In 2008, there was a widespread outbreak of listeriosis in Canada. Twenty-two of the 57 confirmed cases died, with listeriosis playing either an underlying or contributing role as the cause of death (source: website Public Health Agency of Canada). The outbreak could be linked to two production lines of a plant in the neighborhood of Toronto. Since the bacteria were transferred through deli meats, which are cooked, the contamination likely occurred during packaging. There were more than 200 possibly contaminated products. Costs of the recall alone were said to have exceeded $20 million.  In addition, the damage to the image of the company, as well as the industry as a whole, most probably resulted in lost sales adding up to many times this amount. Hence, the consequences of contamination may be far-reaching, both in human and economic terms. Efforts to reduce risks to human health should focus on risk reduction practices both during the production process of ready-to-eat foods and at home by consumers.

Different legal requirements and regulations exist in different countries and for different foods. With respect to Listeria in ready-to-eat (RTE) foods, the United States has adopted a zero-tolerance policy. In the European Union and Switzerland, up to 100 CFU/g are permitted in RTE foods. However, in September it was announced that the European Commission is now considering a move to zero tolerance as well, since it is deeply concerned with the rise of listeriosis in the EU since 2001.

Application and technical support
“The LISTEX™ P100 phage has been selected from Micreos Food safety’s proprietary collection of food-grade phages based on its ‘performance’ in the killing of the broadest possible selection of strains within the pathogenic species of Listeria monocytogenes,” Offerhaus explains. He goes on to say, “The use of the product can be integrated easily within the daily routine of the normal production process. Our technicians examine each phase of our clients’ production process, provide input into local HACCP programs and provide support during trials – on specific application methods and by optimizing the moment and dosage rate of the LISTEX™ phages.”  Offerhaus adds, “Listeria, in contrast to Salmonella and Campylobacter, is extremely hardy, being able to grow at refrigeration temperatures and in low-oxygen environments, such as in a vacuum-packaged product. Phage treatment at the stage where a contamination is most likely to occur is the logical conclusion. For many foods, this will be at some point prior to packaging. However, cheese for example, is vulnerable to contamination throughout the ripening stage.”

Research and development
Micreos Food Safety has a history of extensive international collaborations with universities and institutes, and with many clients, ranging from local producers to some of the world’s largest multinationals. Results regarding the effect of LISTEX™ P100 phages in foods have been published in peer-reviewed journals, both by Micreos Food Safety, itself, and by others. In a recent study it was concluded that the added phages can be very effective for specific biocontrol of Listeria monocytogenes in contamination-sensitive RTE foods (Guenther et al., 2009: Appl. Environ. Microbiol. 75:93-100). In another recent publication, it was shown that a combination of LISTEX™ P100 phages with a protective Lactobacillus sakei culture could be used successfully to reduce the growth of Listeria monocytogenes during “worst case” storage of deliberately contaminated sliced cooked ham (Holck and Berg, 2009:Appl Environ Microbiol. Aug 28. [Epub ahead of print]).

Besides Listeria monocytogenes, the company also conducts research on Salmonella, E-coli O-157, Staphylococcus aureus (MRSA) and Campylobacter jejuni. Since these bacteria might colonize in animals whose meat is used for human consumption, the possible application of phages during livestock farming is studied, as well as treatment of meat after slaughter.

Mark Offerhaus
Contact Details:
Further information is provided on the following website: or can be obtained from Mark Offerhaus, CEO, Micreos Food Safety.
Telephone: +31 317 421414