Characterization and evaluation of a phage cocktail targeting Salmonella enterica in a Turkey farm

Background: Salmonella enterica is a major food-borne pathogen strongly associated with poultry products, causing over 150 million human infections annually despite extensive control measures. Among its serovars, S. enterica serovar Infantis is highly prevalent on poultry farms and represents an increasing food safety and public health concern. Alternative strategies to reduce Salmonella dissemination are urgently needed, and bacteriophages have emerged as promising biocontrol agents. Results: In this study, we enriched and characterized a phage cocktail recovered from wastewater and propagated with Salmonella Infantis. The cocktail underwent a comprehensive stability evaluation, including tolerance to a range of temperatures (4–50 °C), acidic conditions (loss of infectivity at pH 2 and pH 4), and oxidative stress (remaining stable after exposure to hydrogen peroxide concentrations up to 100 ppm). It demonstrated the ability to reduce preformed Salmonella biofilms by 39.9%. Genomic characterization was performed via Illumina sequencing, revealing the presence of nine phages belonging to a distinct genera (Kuttervirus, Berlinvirus, Jacunavirus, Rosemountvirus, Felixounavirus, Mooglevirus, Zindervirus, Astrithrvirus, and one unclassified). Importantly, virulence factors, antimicrobial resistance genes, or lysogenic elements were not detected in the genomes of eight of the nine phages analyzed; for one phage, incomplete genomic information prevented full assessment, supporting the genetic safety of the cocktail. Field evaluation under commercial turkey-rearing conditions showed that both control and phage treated poultry houses tested negative for Salmonella at the end of the production cycle. Therefore, treatment efficacy could not be conclusively determined. However, the study supports the feasibility and safety of applying enriched phage lysates in a commercial production setting, as phage application did not adversely affect production parameters. Conclusions: These findings support the use of well-characterized enriched lysates, as promising candidates for biocontrol strategies to improve food safety and reduce the burden of Salmonella in poultry production systems.