Characterization and encapsulation of a Salmonella phage cocktail for the biocontrol potential of Salmonella spp. in gastrointestinal environments

Authors: ZHANG, YUJIE - Oak Ridge Institute For Science And Education (ORISE); CHU, MACKENNA - Hispanic Association Of Colleges & Universities (HACU); Liao, Yen-Te; Salvador, Alexandra; Wu, Vivian

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/3/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary: N/A

Technical Abstract: Salmonella is the primary pathogen causing foodborne outbreaks related to poultry meat and other food products. The continuous emergence of multidrug-resistant bacteria has become a serious food safety issue resulting from the overuse of antibiotics in the poultry industry. Hence, lytic phages are considered an alternative biocontrol method against these bacterial superbugs. The objective of this study was to characterize and encapsulate two-phage cocktail for the biocontrol potential against Salmonella spp in gastrointestinal environments. Two Salmonella phages—D5lw and S4lw—were subjected to whole-genome sequencing and biological characterization, including morphology, antimicrobial activity, and acid stability tests. Further, the two-phage cocktail was used for encapsulation and tested for their stability in vitro gastrointestinal conditions. D5lw had the morphology containing a capsid with approximately 96.7 ± 0.5 nm in diameter and a long contractile tail of about 135.5 ± 0.5 nm in length. S4lw had a capsid approximately 64.5 ± 0.5 nm in diameter and a long non-contractile tail of 132.3 ± 0.5 nm in length. The taxonomic classification indicated that phage D5lw and S4lw belonged to the Straboviridae and Guernseyvirinae families, respectively. No virulent, antibiotic resistance or lysogenic genes were detected in the two phage genomes. The antimicrobial activities showed that the each phage could infect diverse Salmonella spp, such as S. Enteritidis and S. Typhimurium. Moreover, the phage cocktail can completely inhibit these Salmonella strains for at least 14 hours with an MOI of 100 or 1000 at 25 °C. Further, the acid stability results showed that both free phages and bead-encapsulated phages were stable at pH4 to pH7. The bead-encapsulated phage cocktail could withstand low pHs (pH2 and pH3) for at least 1hour, while most free phages were not detectable. Moreover, bead-encapsulated phages, in comparison to free phages, have higher viability in the simulated gastric and intestinal fluid after 1-hour treatment, demonstrating a protective effect of encapsulation against acid stress. These findings provide valuable insights into the Salmonella phage cocktail (D5 and S4) as a potential biocontrol agent of Salmonella spp in the poultry industry via an oral delivery application.