Final Report Summary - PHAGEVET-P (Veterinary phage therapies as alternatives to antibiotics in poultry production)
The PHAGEVET-P project aimed at evaluating the potential use of phages as alternatives to antibiotics in poultry production and to characterise the efficacy of phages from farm-to-fork. The numbers of reported outbreaks of food-borne diseases and pathogen presence in food-stuffs, continues to climb to unlikely figures, considering the general improvement in food safety knowledge and good practices. The two major important pathogens involved in food-outbreaks and surveys are salmonella and campylobacter.
A study by the Department of Environment, Food and Rural Affairs pointed out the growing resistance of food-borne pathogens to antimicrobials used during animal production and warns processors about the risks of these resistant pathogens passing through the food chain to consumers. Bacteriophages have proven their efficacy as therapeutic agents, in both human clinical settings and animal disease research models. Actual and productive research on this matter strongly supports the concept that bacteriophage therapy can be developed as an alternative to antibiotics. The number of works published, including some reviews, clearly shows that the scientific community finally opened its mind to the tremendous potential of bacteriophages in the control of pathogenic or undesirable bacteria.
Stated targets of PHAGEVET-P were the characterisation of the efficacy of phages from farm-to-fork and input in poultry food safety, including the promotion of knowledge transfer on phage use as alternatives to antibiotics from Eastern Europe, allowing the establishment of an industry-based project follow-up framework. The main scientific objectives were to establish that in live poultry, treatment with specific phages can reduce or eliminate the occurrence of the two pathogens responsible for the majority of human food-borne illness, namely salmonella and campylobacter spp. and to establish that this protection of the live birds from infection provides poultry products for human consumption that have greatly reduced contamination levels with these two pathogens.
Several phages active against salmonella and campylobacter were isolated from sewage water and poultry carcasses. These phages were tested against a pool of food and clinical isolates of salmonella enterica enteritidis and campylobacter coli and campylobacter jejuni (total of 200 strains), which enabled the characterisation of their lytic spectra. Phages having the broader lytic spectrum were fully characterised and used in the in vivo trials and production experiments. Characterisation involved:
- Scanning electron microscope (SEM) analysis for morphology;
- DNA restriction profile for DNA size;
- hybridisation with host pathogens, for DNA homology;
- in vitro activity under simulated GI tract conditions;
- susceptibility to GI tract conditions and phage-host bacteria interaction, phage infection parameter (burst size and latency period).
It must be stressed that the phages selected are strictly lytic and do not encode toxins. One of the campylobacter phages was sequenced being the first campylobacter coli phage to be sequenced and the data will be deposited in GenBank.
In vivo trials demonstrated that phage therapy of poultry can dramatically reduce the numbers of colonising campylobacters and salmonellas. An average 3.1 log and 1.98 log reductions in salmonella and campylobacter numbers were achieved, respectively. Oral gavage or incorporation in food are two feasible and effect routes of phage administration, conversely aerosolised phage had no effect on the numbers of campylobacter colonising the chickens. In addition, there was no phage detected in the faeces at any point post administration.
Based on the in vivo results, it is recommended that the phages are administered one day pre-slaughter in order to achieve the best phage efficacy and to minimise the risk of resistance developing, e.g. in the rearing environment. This recommendation is based on the large but short-lived reduction in pathogen numbers within one day of phage administration, therefore maximising the reduction in pathogen load. Moreover, one day pre-slaughter administration would reduce the time that the pathogen has in contact with the phage and therefore reduce the time for resistance to phage to emerge.
A study by the Department of Environment, Food and Rural Affairs pointed out the growing resistance of food-borne pathogens to antimicrobials used during animal production and warns processors about the risks of these resistant pathogens passing through the food chain to consumers. Bacteriophages have proven their efficacy as therapeutic agents, in both human clinical settings and animal disease research models. Actual and productive research on this matter strongly supports the concept that bacteriophage therapy can be developed as an alternative to antibiotics. The number of works published, including some reviews, clearly shows that the scientific community finally opened its mind to the tremendous potential of bacteriophages in the control of pathogenic or undesirable bacteria.
Stated targets of PHAGEVET-P were the characterisation of the efficacy of phages from farm-to-fork and input in poultry food safety, including the promotion of knowledge transfer on phage use as alternatives to antibiotics from Eastern Europe, allowing the establishment of an industry-based project follow-up framework. The main scientific objectives were to establish that in live poultry, treatment with specific phages can reduce or eliminate the occurrence of the two pathogens responsible for the majority of human food-borne illness, namely salmonella and campylobacter spp. and to establish that this protection of the live birds from infection provides poultry products for human consumption that have greatly reduced contamination levels with these two pathogens.
Several phages active against salmonella and campylobacter were isolated from sewage water and poultry carcasses. These phages were tested against a pool of food and clinical isolates of salmonella enterica enteritidis and campylobacter coli and campylobacter jejuni (total of 200 strains), which enabled the characterisation of their lytic spectra. Phages having the broader lytic spectrum were fully characterised and used in the in vivo trials and production experiments. Characterisation involved:
- Scanning electron microscope (SEM) analysis for morphology;
- DNA restriction profile for DNA size;
- hybridisation with host pathogens, for DNA homology;
- in vitro activity under simulated GI tract conditions;
- susceptibility to GI tract conditions and phage-host bacteria interaction, phage infection parameter (burst size and latency period).
It must be stressed that the phages selected are strictly lytic and do not encode toxins. One of the campylobacter phages was sequenced being the first campylobacter coli phage to be sequenced and the data will be deposited in GenBank.
In vivo trials demonstrated that phage therapy of poultry can dramatically reduce the numbers of colonising campylobacters and salmonellas. An average 3.1 log and 1.98 log reductions in salmonella and campylobacter numbers were achieved, respectively. Oral gavage or incorporation in food are two feasible and effect routes of phage administration, conversely aerosolised phage had no effect on the numbers of campylobacter colonising the chickens. In addition, there was no phage detected in the faeces at any point post administration.
Based on the in vivo results, it is recommended that the phages are administered one day pre-slaughter in order to achieve the best phage efficacy and to minimise the risk of resistance developing, e.g. in the rearing environment. This recommendation is based on the large but short-lived reduction in pathogen numbers within one day of phage administration, therefore maximising the reduction in pathogen load. Moreover, one day pre-slaughter administration would reduce the time that the pathogen has in contact with the phage and therefore reduce the time for resistance to phage to emerge.