Genomic characterization of novel lytic phage vB_Sal_S6 with putative host FhuA interaction and its application for Salmonella biocontrol in milk

Global foodborne Salmonella outbreaks pose a serious concern for food safety and public health underscoring the need for isolation of lytic phages with potential as biocontrol agents. A lytic bacteriophage vB_Sal_S6 was isolated which targets Salmonella serovars - Typhimurium, Bovismorbificans, Infantis, Typhi, Paratyphi, Weltevreden, Poona and as well as Escherichia coli. It exhibited strong bacteriolytic activity across a range of MOIs (0.01-10), with stability across pH 4-10 and temperature conditions (25-55 °C). In artificially contaminated milk, vB_Sal_S6 reduced Salmonella counts by 3.9log at RT and 2.4log at 4 °C within 9 and 6 h respectively (MOI 10). Genomic characterization revealed a dsDNA genome of 36,127 bp length and the absence of virulence, integrase, excisionase, and antibiotic resistance genes, supporting its suitability for biocontrol. Phylogenetic analysis indicated that vB_Sal_S6 clustered with other Salmonella/E.coli phages in Tequintavirus genus within Demerecviridae family. Docking studies identified that ORF123-encoded receptor-binding tail protein binds with ferrichrome receptor FhuA in Salmonella and E.coli as putative receptor. These findings establish vB_Sal_S6 as a promising candidate for biocontrol applications against Salmonella and E. coli.