Killing two poultry bugs with one therapy without risk of resistance
The European poultry business is exceptionally important to the economy. With more than 40 000 poultry farms, 12 million tonnes of meat and around 10 million tonnes of eggs produced, the annual turnover in Europe is EUR 30 billion. Avian colibacillosis and salmonellosis are the main bacterial infections in the poultry sector, with a massive economic impact. The European Food Safety Authority estimate the overall economic burden of human salmonellosis at EUR 3 billion annually. The overuse of antibiotics represents another important challenge to control these bacteria, with the ever-present health threat of antimicrobial resistance. The EU-funded PHAGOVET has devised a cost-effective alternative to control both microbes.
Phages and antiseptic cocktail
“Bacteriophages, or phages, are viruses that specifically infect and kill bacteria without negative effects on human or animal cells,” outlines Daniela Silva, project coordinator. During their biological cycle, phages attach to the target bacteria and invade them. “Phage infection is an extremely specific and selective process as phage structures have to match strain-specific variants of bacterial receptors,” Silva explains. Phage specificity is a double-edged sword, however, as one type of phage cannot annihilate all the bacterial strains present. PHAGOVET’s answer to this is a phage cocktail, the PHAGOVET biocide, mixed to target a spectrum of Salmonella strains. To further increase product efficacy, ‘technological feed additives’ containing bacteriophages against both E. coli and Salmonella are applied to feed or drinking water.
Triumphant trials are not without tribulations
Another issue the team took into account is the different rate of mutation of the bacteria in question. Due to the high mutation rate of E. coli, the use of phage-based products is more of a challenge when compared with Salmonella which is much more ‘stable’ genetically than E. coli. “Although there can be a cocktail with a fixed formulation for immediate action, the laboratory must always isolate the bacteria and tested against the available phage bank. If needed the cocktail formulation must be adapted to every specific situation,” Silva says. The team have adapted to this constraint with a large phage library and very well characterised phages. “Then with the E. coli identified, the best combination of phages can be mixed and given to the animals for the most successful treatment,” concludes Silva. Studies show a significant reduction of Salmonella colonisation two weeks post infection in animals treated with the PHAGOVET zootechnical additive. “Most promising are results regarding the secretion of Salmonella to the environment by Salmonella-infected birds,” Silva notes. “The PHAGOVET-treated group have almost non-existent shedding of Salmonella into the environment compared with the control group and also statistically lower Salmonella counts in the caecum of PHAGOVET-treated birds in the first two weeks post infection.” The PHAGOVET biocide results are also good – there is a significant lowering of Salmonella contamination on surfaces where applied.
Carving out a future for phage-based products in Europe
“The PHAGOVET project offers a cost-affordable and effective solution to fight the main bacterial pathogens in poultry using a combination of phage-based biocide and technological food additive products,” summarises Silva. Currently there is no regulatory framework where bacteriophages with their specificities can be included. However, the project will continue collecting as much data as possible to make a comprehensive case to the EU authorities for a registration framework for bacteriophage products.
Keywords
PHAGOVET, Salmonella, poultry, bacteriophage, biocide, E. coli, phage therapy, registration
