Characterization of lytic bacteriophage vB_EhoP_ZX13 and its therapeutic potential against Enterobacter hormaechei infection.

Enterobacter hormaechei (E. hormaechei) is an opportunistic pathogen that can cause various animal diseases under certain conditions, including pneumonia, peritonitis, and pyogenic endometritis. The emergence of multidrug-resistant E. hormaechei has severely limited treatment options, highlighting the urgent need for alternative therapeutic strategies such as bacteriophage therapy. In this study, we isolated and characterized a lytic bacteriophage, vB_EhoP_ZX13, from aquaculture samples using E. hormaechei-Eho13 as the host. Morphological analysis revealed that vB_EhoP_ZX13 exhibited typical long-tailed phage characteristics and belonged to the family Straboviridae. It demonstrated the optimal infection efficiency at a multiplicity of infection (MOI) of 1, with a short latent period (5 min) and a high burst size (100 PFU/cell). Furthermore, the phage remained stable at 4-30 °C and pH 5-8, but was sensitive to high temperatures and ultraviolet (UV) light exposure. Genomic analysis revealed a 172,900 bp double-stranded DNA (dsDNA) genome encoding 295 open reading frames (ORFs) and 19 tRNAs. Crucially, no genes associated with virulence factors, lysogenic genes, or antibiotic resistance-related were identified, supporting its biosafety for therapeutic. In vitro, vB_EhoP_ZX13 significantly inhibited the growth of Eho13. In vivo, phage treatment markedly improved the survival rate of infected mice, with a 90 % survival observed when administered at an MOI of 1. In summary, vB_EhoP_ZX13 is a lytic phage with strong antibacterial activity both in vitro and in vivo, highlighting its promise as an alternative therapeutic agent against E. hormaechei infections.