טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentOffer Miri
SubjectUse of Bacteriophage to Reduce Human Bacterial
Pathogens in Food
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Robert Armon
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

The incidence of outbreaks associated with foodborn bacterial pathogens has increased in many countries in the last decade.

One of the methods uses bacteriophages to reduce those pathogens can be of great benefit at each step of the food production process, from the animal growing all the way through butchery, packaging and storing.

A few characteristics make the phages well suitable for this purpose:

         Since bacteria are phages natural enemy, it can be used as biological control on the bacterial population without harming the environments natural flora.

         Phages are highly specific to their host, so the treatments can be targeted to particular pathogens.

         The phages are able to adapt to the host genetic changes during the bacteriophages life cycle.

Although phage has shown some promise, limitations still exist. Such limitations are:

         Only lytic phages were used for therapy. Lysogenic phages don’t match for biocontrol of foodborne pathogens because they integrate and change the host genome. Those changes can cause unpathogenic bacteria to become pathogenic. As opposed to them, the lytic bacteriophages can’t integrate within the host genome. They can cause lyse to the host cell following infection and release of new progeny phages that in turn infect new uninfected adjacent host cells. That advance finds the last one suitable of biocontrol of foodborne pathogens.

         Before using any phage, researchers must be confident that phage is lytic and does’t confers virulence to its host.

         To prevent the problem of resistance, a phage cocktail prepares from strains with different receptor specificity for the pathogenic bacterium.


This review paper intends to briefly summarize and explain the considerations before using of bacteriophage to reduce human bacterial pathogens in food and comparison between conclusions from different studies about limitations and advantages of this approach.  The conclusions divided to food producing animals and fresh produce. For example:

         Both foods producing animals and fresh produces had shown success of reduction of host bacteria. That success of reduction of host bacteria is dependent on the phage dosage and specificity, and the length of time between infection and treatment. The longer the time period between infection with the host and oral administration of phage, the lower the reduction of host bacteria.

         Fruit with a neutral pH could be effectively controlled with a phage cocktail.

         Phage cocktails were more effective than using a single phage strain, and resulted in a lower percentage of resistant mutants.