A new Tequintavirus bacteriophage SIA3lw isolated from sewage water with antimicrobial potential against multidrug-resistant Salmonella Infantis

Authors: Liao, Yen-Te; VOELKER, ANGELA - Hispanic Association Of Colleges & Universities (HACU); CHU, MACKENNA - Hispanic Association Of Colleges & Universities (HACU); Zhang, Yujie; HO, KAN-JU - Texas Tech University; Harden, Leslie; Salvador, Alexandra; Wu, Vivian

Submitted to: mBio
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Salmonella strains are closely associated with antibiotic resistance development, posing a significant risk to public health. A certain group of Salmonella strains, also known as Infantis, has recently caused increasing foodborne contamination. Thanks to the nature of lytic bacteriophages (or phages), these viral populations embrace a promising antibiotic alternative to mitigate multidrug-resistant bacterial pathogens. This study used genomic and biological approaches to reveal the potential antibiotic alternative of a lytic bacteriophage SIA3lw against multidrug-resistant Salmonella Infantis. The results show that phage SIA3lw is a new phage with a long and non-contractile tail and belongs to the Tequintavirus genus. The phage does not contain harmful genes, such as virulence, antibiotic resistance, and lysogenic genes, which can compromise the safety of future phage applications. The biological features indicate that SIA3lw can target different Salmonella Infantis strains of various origins and two generic E. coli strains used in this study. Most importantly, SIA3lw, with 100 times more than the bacterial concentration, reduced over 99.99% of multidrug-resistant Salmonella Infantis strains in 8 hours of the treatment at 25°C. The findings suggest that the new long-tailed phage SIA3lw has the potential as an antibiotic alternative to multidrug-resistant Salmonella Infantis.

Technical Abstract: Salmonella enterica serovar Infantis has considerably contributed to foodborne illness and caused public health concerns in recent years. Due to frequent antibiotic resistance challenges amid Salmonella species, promising antimicrobial alternatives, such as lytic phages, are needed. Thus, the objective was to characterize a new phage isolated from sewage water for its antimicrobial potential against multidrug-resistant S. Infantis. Salmonella phage vB_SalS-SIA3lw (or SIA3lw) has siphovirus morphology with a genome size of 116,541 bp and is genomically classified in the Tequintavirus genus, sharing a close evolutionary relationship with Escherichia phage BF23. However, SIA3lw shared low nucleotide sequence similarities of receptor binding protein (ORF 22) and putative tail fiber protein (ORF 42) genes, both associated with bacterial host recognition and binding, with the counterfeits in the genome of BF23. No genes associated with virulence, antibiotic resistance, and lysogeny were found. For biological traits, SIA3lw has a latent period of 30 min and an estimated burst size of 150 PFU/CFU against S. Infantis ATCC BAA-1675. The phage shows polyvalent antimicrobial activities against various S. Infantis and two generic E. coli strains. Among different phage concentrations, MOI=100 was the most effective in reducing two individual multidrug-resistant S. Infantis strains in vitro at 25°C by more than 4.5 log after 8-h treatment. Moreover, using SIA3lw with MOI=100 significantly reduced the occurrence of phage-insensitive mutants compared to low MOIs after phage treatment. The findings indicate that SIA3lw is a new member of Tequintavirus phages and a potential antibiotic alternative to prevent multidrug-resistant Salmonella Infantis contamination.