Isolation and characterization of a lytic bacteriophage, Vibrio PHZU0002, with biocontrol potential against Vibrio harveyi

The antibiotic resistance of Vibrio harveyi , the primary pathogen that infects marine aquaculture animals, has increased rapidly because of the continuous expansion of intensive farming. This poses significant challenges to disease management in the aquaculture industry. Bacteriophages have emerged as key natural therapies for controlling lysis caused by Vibrio spp. In this study, the double-layer agar method was used to isolate phages that infected V. harveyi , and the morphology of the phages was observed via transmission electron microscopy (TEM). We further assessed host range specificity, the optimal multiplicity of infection (MOI), one-step growth kinetics, and the stability of the bacteriophage under various pH and temperature conditions. Genomic analysis of this phage was conducted using whole-genome sequencing, followed by functional annotation of open reading frames (ORFs) and phylogenetic analysis. Finally, the therapeutic effect of the phage on zebrafish infected with V. harveyi was evaluated. A bacteriophage capable of lysing V. harveyi was isolated using the double-layer agar method and named Vibrio PHZU0002. Based on TEM observations, the phage has an icosahedral head structure with a diameter of approximately 61.90–65.87 nm and a short tail filament structure with a length of approximately 16.09–16.26 nm. Genome sequencing analysis revealed that this bacteriophage belongs to the Zobellviridae family. The genome size was 47,587 bp, the GC content was 43.22%, and it contained 69 coding sequences. This bacteriophage has strong environmental adaptability, maintaining stable activity under conditions of 23–60 °C and a pH of 5.0–11.0. One-step growth curve analysis revealed that Vibrio PHZU0002 had a latent period of 20 min, with an average burst size of 70 PFU/cell and an optimal multiplicity of infection (MOI) of 10. Moreover, Vibrio PHZU0002 can efficiently lyse 9 V. harveyi strains from different sources, and genomic analysis revealed no antibiotic resistance or virulence genes. In vivo treatment of zebrafish infected with V. harveyi demonstrated significant therapeutic efficacy. This study elucidated the biological characteristics of Vibrio PHZU0002 and validated its potential for use in the prevention and control of V. harveyi infection in marine aquaculture animals, providing important support for filling the gap in antimicrobial options against drug-resistant V. harveyi in aquaculture settings.