Isolation and Characterization of Phage vB_KpnS_SXK7 Against Multidrug-Resistant Klebsiella pneumoniae and Mechanism of O-Antigen-Mediated Phage Resistance：Dataset

The increasing prevalence of multidrug-resistant MDR Klebsiella pneumoniae necessitates alternative therapeutic strategies. Here, we isolated and characterized a novel lytic phage, vB_KpnS_SXK7, from hospital sewage and investigated the host’s resistance mechanism. Morphological analysis identified it as a siphophage. It exhibited a 30-min latent period, burst size of 270 PFU/infected cell, and stability across pH 5–12 and temperatures up to 60°C. Whole-genome sequencing revealed a 49.1-kb circular dsDNA genome lacking tRNA, virulence, or antibiotic-resistance genes, confirming its safety profile. In vitro, vB_KpnS_SXK7 reduced bacterial viability within 2 h. In a Galleria mellonella infection model, a single dose (MOI 100) rescued 80% of larvae from lethal challenge without toxicity. Genomic analysis of resistant mutant SXK7-R11 identified a single-nucleotide deletion in wzm, which encodes an ABC transporter permease essential for O antigen assembly. This mutation impaired phage adsorption, which was restored by genetic complementation. These findings establish vB_KpnS_SXK7 as a safe and potent therapeutic candidate but highlight its vulnerability to O-antigen-mediated resistance, supporting the development of phage cocktails targeting multiple receptors against MDR infections.