Public Health Safety of Bacteriophages in Ready-To-Eat Meats & Poultry Products

Recently approval has been given by the USFDA for use of the combination of six bacterial viruses or bacteriophages as a food additive. These bacteriophages are to be used on ready-to-eat meats and poultry to kill strains of listeria monocytogenes prior to their packaging. 

Listeria monocytogenes are of major public health concern because it can cause serious infection in pregnant women, newborns and adults with weaken immune systems. It has been estimated that 2,500 people become seriously ill with listeriosis each year. Hence there is a growing need to develop effective treatments against pathogenic microorganisms such as listeria monocytogenes. The approval of bacteriophages by the USFDA for use in ready-to-eat meats and poultry therefore serves to address this public health problem.

However, it is uncertain whether bacteriophages are safe enough to be used in ready-to-eat meats and poultry without causing any short or long term health effects. Because scientific studies to date have not shown conclusively to confirm or deny the safety of bacteriophages in ready-to-eat meats and poultry. It is hoped that the apparent expeditious use of bacteriophages in the light of insufficient scientific data may not compromise the public's health. The purpose of this article is to bring to the forefront a concise review of the possible public health concerns associated with the use of bacteriophages in ready-to-eat meats.

What are bacteriophages?

The term bacteriophages are derived from the Greek word meaning
"bacteria-eater". Bacteriophages were discovered around 1915 and have contributed significantly to the understanding of viruses or virology. They provide an alternative to costly antibiotics and can be developed mush faster and at a lower cost.

How can bacteriophages be used to control bacteria?

Bacteriophages are first grown in a preparation containing the target bacteria. The preparation is first purified before use on food. The bacteriophages are then sprayed onto ready-to-eat meat and poultry at a concentration of 1 ml per 500 cm2 of food surface. Bacteriophages then seek out bacteria and infect them during its life cycle. The life cycle of bacteriophages can follow either the lytic or lysogenic pathway that results in lysis of the bacterium.

In the lytic cycle, the virulent bacteriophage binds to the bacterium and releases its DNA into the host cell. This triggers a series of events that leads to the lysis of the host cell, resulting in cell dealth. Bacteriophages multiply much faster than bacteria and infect many bacteria in a short time period thereby eliminating them or controlling their growth and numbers to acceptable levels.

In the lysogenic cycle, the temperate bacteriophage binds to the bacterium and releases its DNA into the host cell, which then binds to the host cell DNA and form a prophage. This prophage has the potential to lyse the resulting bacterium causing dealth.

Are bacteriophages safe to consume?

Bacteriphages are bacteria-viruses. Viruses contain either DNA or RNA in their genetic make. This genetic material is believed to be transferred only to bacterial cells and not normal cells. But, has this specificity been rigorously tested in experimental animals/models and demonstrated in clinical trials? Strong scientific evidence is lacking and there is an urgent need for more research in this area. Viruses may induce an immunological response in vivo and in normal cells causing the development of secondary infections especially in susceptible individuals such as young children, old people, pregnant women and immuno compromised persons with HIV/AIDS.

What are some of the public health concern regarding the safety of bacteriophages?

Some of the public health concerns regarding the safety of bacteriophages include:

o Failure to select specific phages against the target bacteria in vitro, before using them on ready-to-eat meats and poultry may increase the possibility of developing secondary infections.

o Lack of availability and/or reliability of bacterial laboratories for carefully identifying the pathogens involved, therefore making selection of specific phage very difficult.

o Endotoxins can be released as a result of lysis of bacteria which could lead to health complications such as liver edema and pain in the associated abdominal region if meat or poultry is improperly cooked.

o Lack of thorough understanding of the heterogeneity and "mode of action" (lytic or lysogenic modes of action) of bacteriophages may affect their ability to destroy target bacteria.

o Bacteria resistant bacteriophages and the apparent ineffectiveness of bacteriophages to kill target bacteria.