Gastrointestinal Dynamics of Non-Encapsulated and Microencapsulated Salmonella Bacteriophages in Broiler Production

SIMPLE SUMMARY: Bacteriophages are viruses that kill targeted bacteria and could be used as a therapy against multidrug-resistant bacteria in animal production. Gastrointestinal tract conditions throughout the broiler production cycle might compromise the efficacy of bacteriophage oral administration against Salmonella. Microencapsulation of phages could protect and prevent the premature release of the bacteriophage, thereby allowing targeted delivery to the colonization site of Salmonella, the caecum. This study was designed to assess the optimal timing of the phage intervention over a 42-day production cycle and to compare microencapsulated (delivered in animal feed) and non-encapsulated phages (delivered through the drinking water) delivery along the gastrointestinal tract. Results of this study suggest that microencapsulation of the phages in a Eudragit(®) L100 pH-responsive formulation allowed targeted delivery of the phage to the chicken caecum. Microencapsulation of phages administered orally through animal feed could be a promising method to control Salmonella in the field at any time during the animal rearing period. ABSTRACT: Bacteriophage therapy is being considered as a promising tool to control Salmonella in poultry. Nevertheless, changes in gastrointestinal tract environmental conditions throughout the production cycle could compromise the efficacy of phages administered orally. The main objectives of this study were to assess the optimal timing of the phage administration over a 42-day production cycle and to compare microencapsulated and non-encapsulated phages and the spatial and temporal dynamics of the phage delivery along the gastrointestinal tract. Phage FGS011 was encapsulated in the pH-responsive polymer Eudragit(®) L100 using the process of spray drying. At different weeks of the chicken rearing period, 15 broilers were divided into three groups. Over a period of 24 h, group 1 received non-encapsulated phages (delivered through drinking water), group 2 received microencapsulated phages (incorporated in animal feed), and group 3 did not receive any phages. Microencapsulation was shown to enable efficient delivery of the bacteriophages to the animal gut and cecum throughout the animal rearing period. During the six weeks of application, the crop displayed the highest phage concentration for both phage delivery methods. The L100 based encapsulation offered significant protection to the phages from the harsh environmental conditions in the PV-Gizzard (not seen with phages administered in drinking water) which may help in the delivery of high phage doses to the cecum. Future Salmonella challenge studies are necessary to demonstrate the benefits of microencapsulation of phages using L100 formulation on phage therapy in field studies during the rearing period.