Lytic phage vB_AhS_LZ: A promising green alternative to antibiotics for Aeromonas hydrophila biocontrol

This study isolated a novel Aeromonas hydrophila phage vB_AhS_LZ, focusing on its biological characteristics, genomic features, in vitro antibacterial/biofilm-eradicating activity, therapeutic efficacy in zebrafish, and application in chilled salmon fillet preservation. Findings will enrich Aeromonas-specific phage resources and lay a foundation for developing food-grade biocontrol agents against A. hydrophila in aquaculture and food processing.A. hydrophila is a major pathogen threatening aquaculture sustainability and food safety, with antibiotic overuse leading to multidrug resistance. Here, a lytic phage vB_AhS_LZ targeting A. hydrophila was isolated from sea cucumber aquaculture wastewater and classified into the family Siphoviridae. Morphological, biological, and genomic characteristics were systematically analyzed, and its biocontrol potential was evaluated in vitro, in zebrafish models, and in refrigerated salmon. vB_AhS_LZ exhibited an icosahedral head(~80 nm) and non-contractile tail(~100 nm), with a short latent period(15 min), high burst size(237 PFU/cell), and optimal multiplicity of infection(MOI=0.1). It maintained stable activity at 4–50 °C and pH 3–10, and was tolerant to 1% chloroform. Whole-genome sequencing revealed a 40,084 bp dsDNA genome(G+C=48.79%) encoding 45 ORFs, with no virulence, antibiotic resistance, or lysogeny-associated genes, confirming biosafety. In vitro assays showed vB_AhS_LZ efficiently lysed planktonic A. hydrophila and inhibited biofilm formation by 60.6± 3.2%. In zebrafish, it exerted dose-dependent therapeutic efficacy(60% survival at MOI=1) and alleviated tissue damage. In refrigerated salmon(4 °C), it reduced A. hydrophila counts by up to 4.7 log10 CFU/mL over 120 h. Comparative genomics indicated cross-genus homology with Escherichia phages, with modular variations supporting A. hydrophila specificity. These findings demonstrate that vB_AhS_LZ is a safe and effective biocontrol agent, providing a green alternative to antibiotics for A. hydrophila control in aquaculture and aquatic product preservation.