Characterization and genome analysis of a novel lytic phage vB_ntSalS-cftriSP11 infecting Salmonella typhimurium.

BACKGROUND

In response to rising antibiotic resistance, bacteriophage application is gaining renewed attention, marking a paradigm shift in managing bacterial infections, especially foodborne pathogens. Non-typhoidal salmonellosis remains a major global health burden. In this context, a novel lytic bacteriophage targeting Salmonella typhimurium was isolated and characterized.

METHODS AND RESULTS

A novel phage, vB_ntSalS-cftriSP11, targeting S. typhimurium, was isolated using spot and double agar overlay methods. One-step growth analysis showed a burst size of 146 ± 10 particles with a 20 min latency period. The phage exhibited a broad host range and stability across a wide pH and temperature range. Morphological and genomic analyses identified it as a member of Casjensviridae, with a 56,837 bp genome encoding 103 of 105 predicted ORFs linked to biological processes, cellular components, and molecular functions. Notably, no toxin genes, virulence factors, or antimicrobial resistance genes were detected in the genome. BLAST and phylogenetic analyses revealed high sequence similarity (97-98%) with known Salmonella phages 35, 37 and PK4. Functionally, the phage demonstrated strong anti-Salmonella activity, reducing biofilm biomass by 1.86-fold and 2.11-fold in 48- and 72-h-old biofilms, respectively, after 24 h of treatment. It also significantly decreased Salmonella counts on chicken breast samples at RT and 4 ℃ at MOI 1 compared to the culture control.

CONCLUSIONS

The Phage vB_ntSalS-cftriSP11 was identified as a stable, lytic bacteriophage with a broad host range and strong antibiofilm activity against S typhimurium. Its genetic safety profile and efficacy highlight its potential as a promising biocontrol agent against antibiotic-resistant Salmonella infections.