HEAL ▶▶▶TH


Enzybiotics are proteins (enzymes) with bactericidal activi- ties. In the context of phage therapy, enzybiotics are proteins coded by phages. Enzybiotics are capable of destroying cer- tain bacteria, when they are being added externally. The ma- jority of the enzybiotics are endolysins, and are derived from phages. The specific function of these endolysins is to de- stroy the bacteria that is host to the phages, so newly creat- ed virus particles can be set free, once the multiplication cycle has been finished, see Figure 2.


Drawing of a phage attacking bacteria. Pros and cons


When suggesting a novel substance as an antimicrobial, an evaluation requires a comparison with existing methods regarding its pros and cons.


1. Bacteriophages are micro-organisms that are extraordinarily abun- dantly available, as they can be found in their normal form in the environment. For instance, they have been isolated in soil samples at a density of 108 particles/g. This means that humans, animals and plants are in contact with phages for most of our lives without them causing apparently adverse reactions.


2. The antimicrobial action of bacteriophages and enzybiotics is very specific. When used in a therapy, they only target that specific path- ogenic bacteria and the rest will remain untouched.


3. Whether applied to antibiotic resistant bacteria or to susceptible bacteria, the elimination efficacy of bacteriophages and enzybiotics is identical.


4. Bacteriophages multiply when infecting pathogenic bacteria, con- sequently increasing their antimicrobial properties.


5. Enzybiotics act on essential targets for the bacteria’s viability and for that reason, it is difficult for bacteria to modify them. This appears to be the reason why until now there has not been any description of bacteria resistant to enzybiotics.


34 ▶ POULTRY WORLD | No. 1, 2019


Antimicrobials derived from bacteriophages, however, do have a cou- ple of disadvantages.


1. Acceptation by part of the society may be an issue, as bacteriophag- es are associated with dangerous viruses. These viruses, however, are totally specific to these bacteria and for that reason, they are harmless to humans, animals, plants or the environment.


2. The usage of bacteriophages requires a detailed study of its biology as well as of its genetic characteristics. The goal of this research should be to assure that in no case are the phages carriers or capa- ble of transmitting virulence factors to other bacteria.


3. The specificity of the bacteriophages for their target bacteria is very high, which means that, to make sure that all strains will be elimi- nated, it is necessary to use a mixture of various phages with a dif- ferent host range.


4. The appearance of resistance against phage-derived antimicrobials might be a theme of concern. In the case of bacteriophages, bacte- ria can become resistant to these. Using a mixture of different phag- es minimises the probability of acquiring resistance to those. It is good to note that there have not been any descriptions of bacteria being resistant to enzybiotics, although numerous studies of repeat- ed exposure to subinhibitory quantities of them have been made.


Current status of phage therapy The number of studies about phage therapy is growing, indi- cating that more data will become available about phage and enzybiotic efficacy and safety, especially with regard to the elimination of pathogenic bacteria in human health, ani- mal health or the environment. Noteworthy is the significance of research by some, mostly US-based biotechnology-based companies, as they received permission for various products. These products can be used in different segments of the agribusiness production chain, from the treatment or prevention of disease in farm animals, to the disinfection of farm houses. The following applications are available in relation to agriculture. • AgriPhage (Intralytix, USA) is a commercially available product which consists of a mixture of phages which are active against pathogenic bacteria for plants. Its goal is to


PHOTO: MONIKA WISNIEWSKA


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