Isolation and Characterization of a Cold-Adapted Bacteriophage for Biocontrol of Vibrio parahaemolyticus in Seafood

Vibrio parahaemolyticus (V. parahaemolyticus) is a preeminent seafood-borne pathogen, imposing significant economic burdens on global aquaculture. The escalating prevalence of multidrug-resistant strains has accentuated the critical urgency for developing sustainable biocontrol strategies. In this study, a bacteriophage designated vB_VPAP_XY75 (XY75) was isolated and biologically characterized to establish an effective control against V. parahaemolyticus. XY75 exhibited remarkable specificity toward V. parahaemolyticus, effectively lysing 46.2% of the target strains while showing no lytic activity against non-target bacterial species. Morphological characterization confirmed its taxonomic assignment to the Myoviridae family, featuring an icosahedral head (40 ± 2 nm) and contractile tail (60 ± 2 nm). XY75 demonstrated strong environmental tolerance, remaining stable at pH 4-11 and temperatures as high as 50 °C. At an optimal multiplicity of infection (MOI = 0.01), XY75 achieved a peak titer of 8.1 × 10¹⁰ PFU/mL, a 5 min latent period, and burst size of 118 PFU/cell. Critically, XY75 reduced V. parahaemolyticus in salmon by more than 5.98 log CFU/g (99.9%) within 6 h at 4 °C, demonstrating exceptional cold tolerance and lytic activity. Genomic analysis confirmed that no virulence or antibiotic resistance genes were present. These results establish XY75 as a safe and efficacious biocontrol candidate for seafood preservation, with particular utility under refrigerated storage conditions.