A lytic vibriophage as a potential biocontrol agent against vibriosis in aquaculture

Vibrio alginolyticus poses a common threat to seafood, resulting in substantial losses in aquaculture and increasing the risks to human health through seafood-borne infections. With the emergence of multidrug-resistant strains, more attention has been paid to phages as a potential alternative or supplement to antibiotics for biocontrol. In this study, a siphovirus, named vB_ValS_R23Z (R23Z), was isolated from shrimp aquatic water and showed specific infectivity against V. alginolyticus ATCC 17749^T, with a latent period of approximately 60 min and a burst size of 58 ± 16 plaque-forming units per cell. Genome analysis revealed that phage R23Z possesses two lysis genes, with no lysogenic, antibiotic resistance or virulence genes detected, underscoring its high lytic capacity and genetic safety. Notably, phage R23Z had a broad host range, efficiently lysing over 16 Vibrio strains across four species. It performed well across a wide temperature range (4°C-45 °C) and pH range (4-9), and displayed high lytic efficiency against V. alginolyticus ATCC 17749^T at all tested multiplicity of infections (0.01, 0.1, 1, 10 and 100), suggesting adaptability and effectiveness to diverse aquaculture conditions. Additionally, in vivo trials revealed that R23Z application as a single phage therapy significantly enhanced shrimp survival rates (>16 %) during V. alginolyticus infection period, underscoring its practical efficacy in aquaculture. These findings position R23Z as a safe, effective, and environmentally adaptable biocontrol agent against Vibrio infections in aquaculture, with significant potential for applications in disease prevention and food safety, either as a standalone treatment or as part of phage cocktails.