Isolation and Characterization of a Novel Thermostable Bacteriophage Targeting Multi-Drug-Resistant Salmonella Enteritidis.

(1) Background: The emergence of multidrug-resistant (MDR) Salmonella enterica poses a major threat to global public health, underscoring the urgent need for alternative therapeutic strategies. Bacteriophages represent a promising alternative due to their high specificity and potent ability to lyse MDR strains. (2) Methods: In this study, we isolated a novel MDR Salmonella Enteritidis-targeting bacteriophage from Lebanese sewage and characterized its host range, thermal and pH stability, and infection dynamics. Whole-genome sequencing was performed using Illumina technology to determine its genetic features and taxonomic classification. (3) Results: the bacteriophage was classified within the genus Jerseyvirus and the class Caudoviricetes with a 43 kb dsDNA genome encoding 66 open reading frames (ORFs). It demonstrated remarkable thermal stability, retaining infectivity after prolonged incubation at 65 °C, and showed a broad host range. The phage formed large, clear plaques, displayed rapid adsorption (>97% within 3 min), a short latent period (20 min), and a burst size of ~32 PFU per cell. Genome analysis revealed no lysogeny, virulence, or resistance genes, confirming its strictly lytic nature and supporting its potential use as a biocontrol agent. (4) Conclusions: These findings identify SA01 as a novel, strictly lytic, and thermally stable bacteriophage with strong potential as a biocontrol agent against multidrug-resistant Salmonella Enteritidis. Its broad host range suggests potential activity also against other Salmonella enterica serovars, supporting its applicability in food safety and biotechnology.