Characterization, lytic activity, and therapeutic efficacy of a novel phage, BUCT789, lysing drug-resistant Escherichia coli in Galleria mellonella larvae.

Severe infections caused by multidrug-resistant Escherichia coli (E. coli) highlight the necessity for new therapeutics. Phage therapy is an alternative treatment approach for multidrug-resistant E. coli infections. Here, we report the isolation and characterization of a novel phage, BUCT789, from hospital sewage. Phage BUCT789 exhibits a short latent period (30 min), a large burst size (∼220 PFU/cell), rapid adsorption (>90% within 20 min), and broad stability across 4-45 °C and pH 3-12. Genomic analysis reveals a 40,771-bp double-stranded DNA genome (G + C 50.9%) encoding 69 ORFs, with no virulence or antibiotic resistance genes, supporting biosafety for therapeutic use. Phylogenetic analysis places BUCT789 within the genus Kagunavirus (subfamily Guernseyvirinae), representing a putative new species. In vitro, BUCT789 rapidly inhibits E. coli growth within 2 h and significantly inhibits biofilms. In vivo, treatment increases Galleria mellonella survival from 10% to 90%. These features highlight BUCT789 as a promising candidate for developing safe and effective phage-based therapeutic interventions against multidrug-resistant E. coli.