Study: In-feed phage cocktail reduced salmonella colonization in challenged birds
A trial backed by feed company, AB Agri, and led by University of Leicester researchers, Dr Anisha Thanki and Professor Martha Clokie, showed the phage based liquid product prevented the bacterial infection developing in the birds.
The phage used within the trial was developed in the University’s new Leicester Centre for Bacteriophage Research, which is studying such products to prevent and treat bacterial infections in humans, animals and in agriculture.
Phages are viruses that infect and kill bacteria. In contrast to antibiotics, they target specific bacteria and thus represent a promising alternative for fighting harmful bacterial pathogens.
The researchers said they hope the product, which could be administered directly to poultry and targets multiple strains of Salmonella common throughout UK farming, will eventually be available for use in commercial poultry production.
Their trial used 672 broiler chickens, split across six control groups, to evaluate whether the bacteriophage was effective in differing doses.
“We tested whether the bacteriophage product delivered in feed at different doses wiped out Salmonella in chickens over a 42-day period. We found that all those infected and treated with the lowest dose at the beginning of the trial tested negative for Salmonella on day 42,” said Dr Thanki.
Phage treatment at all three doses had a positive impact on growth performance in challenged birds with increased weight gains in comparison to challenged birds with no phage diet.
"We showed delivering phages via feed was effective at reducing Salmonella colonization in chickens and our study highlights phages offer a promising tool to target bacterial infections in poultry.”
Regulatory bodies may require dose response data when assessing efficacy and safety of phage products. “Furthermore, obtaining phage dose response data increases the likelihood of identifying an economic optimum for delivery of treatments,” said the researchers in a summary of the trial published in the scientific journal, Emerging Microbes and Infections.
Application in feed
The phage cocktail was delivered to the birds in the trial by mixing liquid phages into the mash diet of starter, grower, and finisher feed and the phage cocktail was stable within the diet.
Adding the phage cocktail after manufacturing the diet was necessary as heat and high pressures used during the production process could affect phage viability, especially phages in liquid.
“Commercially, this could be a viable option for phage delivery in feed; additives are currently being added to final feed products, such as by mixing with or spraying on feed.”
Other potential delivery options could be drying the phages with excipients, which protect during the drying process and then mixing the dried phages with feed and pelleting at commercial scale, said the research team.
While they have shown that this route is viable, the team noted that as the drying excipients assessed are expensive it would add extra costs to manufacturing.
The experts said that future research will focus on investigating the safety of phage therapy by determining the impact of phages on the microbiome of chickens and use histopathology to determine pathological impact, if any, of phage infection in chicken organs.
Regulatory landscape
Despite their promise in several applications, the commercialization of bacteriophage-based products for use in human and animal health is rife with challenges, reports Fixed Phage.
“The regulatory landscape is ever-changing, and there is a lack of clear regulatory guidelines or processes. There is currently a push for better regulatory guidelines, and a collaborative effort involving UK Phage Therapy, CPI, FixedPhage, and the University of Leicester’s Centre for Phage Research is working to establish a novel infrastructure for the provision of phage therapy in the UK.”
