A new Epseptimavirus bacteriophage vB_SalS-SIY1lw as a potential antimicrobial alternative to multidrug-resistant Salmonella Infantis

Authors: Liao, Yen-Te; VOELKER, ANGELA - Hispanic Association Of Colleges & Universities (HACU); ARELLANO, ABIGAIL - Hispanic Association Of Colleges & Universities (HACU); Zhang, Yujie; Harden, Leslie; Salvador, Alexandra; Wu, Vivian

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2025
Publication Date: 2/5/2026
Citation: Liao, Y., Voelker, A., Arellano, A., Zhang, Y., Harden, L.A., Salvador, A., Wu, V.C. 2026. A new Epseptimavirus bacteriophage vB_SalS-SIY1lw as a potential antimicrobial alternative to multidrug-resistant Salmonella Infantis. Scientific Reports. 16. Article 5376. https://doi.org/10.1038/s41598-025-31311-8.
DOI: https://doi.org/10.1038/s41598-025-31311-8

Interpretive Summary: Salmonella Infantis has become one of the most prevalent groups of pathogenic Salmonella primarily due to its antibiotic resistance and high persistence to environmental stresses. Therefore, the presence of these pathogens and their spread to humans pose tremendous problems. Lytic bacteriophages (or phages) are bacterial viruses that embrace a promising solution to mitigating multidrug-resistant bacterial pathogens. This study used genomic and biological approaches to reveal the antimicrobial potential of a lytic bacteriophage SIY1lw against multidrug-resistant Salmonella Infantis. The results show that phage SIY1lw is a new phage with a long and non-contractile tail and belongs to the Epseptimavirus genus, sharing no close evolutionary relationship with the reference phages in this study. The phage does not contain harmful genes, such as toxins, antibiotic resistance, and lysogenic genes, which can jeopardize future phage application safety. The biological features indicate that SIY1lw can target various Salmonella Infantis strains, Salmonella Newport, and two generic E. coli strains used in this study. Most importantly, SIY1lw, with 1,000 times more than the bacterial concentration, reduced over 99.99% of Salmonella Newport and multidrug-resistant Salmonella Infantis strains within 6 hours of the treatment at 25°C. The findings suggest that the new phage SIY1lw has antimicrobial potential against pathogenic Salmonella strains, including multidrug-resistant Salmonella Infantis.

Technical Abstract: Salmonella Infantis is an emerging Salmonella serovar, contributing to increasing foodborne illness in recent years. Novel antimicrobial agents, such as lytic bacteriophages, are alternative to mitigate these pathogens primarily due to the issue of antibiotic resistance among most Salmonella species. Thus, the objective was to characterize a new Epseptimavirus phage with antimicrobial activity against various antibiotic-resistant S. Infantis strains. Salmonella phage vB_SalS-SIY1lw (or SIY1lw) has a siphovirus morphology and double-stranded DNA with a genome length of 123,932 bp (GC content of 40.3%). Phage SIY1lw is genomically classified in the Epseptimavirus genus, sharing no close evolutionary relationship with any reference phages at the nucleic acid level in this study. SIY1lw shared high nucleotide sequence similarities of receptor binding protein (ORF 23) and tail fiber protein (ORF 43) genes—both associated with bacterial host recognition and binding—with the counterfeits in Salmonella phage OSY-STA (the Epseptimavirus genus) and Escherichia phage DaisyDussoix (the Tequintavirus genus), respectively. No virulence, antibiotic resistance, or lysogeny genes were found. For biological traits, SIY1lw has a latent period of 30 minutes and an estimated burst size of 42 PFU/CFU. The phage had polyvalent effects against S. Infantis, S. Newport, and non-pathogenic E. coli (ATCC 15597 and ATCC 13706) strains. The in vitro antimicrobial activity test showed that the phage with MOI=1,000 is the most effective in reducing S. Infantis and S. Newport by 1 and 1.7 log, respectively, over 6-h treatment. These findings indicate that the new Epseptimavirus phage SIY1lw has antimicrobial potential against S. Newport and antibiotic-resistant S. Infantis.