Efficient elimination of highly lethal Vibrio parahaemolyticus in shrimp aquaculture by a vibriophage

Vibriosis, caused by Vibrio species, is the most prevalent bacterial disease in aquaculture, causing significant harm to aquatic animals and serious economic losses. The overuse of antibiotics has led to rising bacterial resistance and reduced treatment efficacy, prompting the development of phage therapy as a sustainable alternative for controlling vibriosis in aquaculture. Here, a lytic phage vB_VpaS_R32L (R32L), targeting V. parahaemolyticus vp-HL-202005, the causative agent of highly lethal Vibrio disease (HLVD), was isolated and comprehensively characterized in terms of morphology, infection dynamics, environmental stability, genomic features, host range, and bacteriolytic efficacy. Phage R32L rapidly formed plaques with an expansion rate of approximately 2.51 μm min^-1 and exhibited a short latent period of approximately 10 min, along with a high burst size of 149 ± 23 PFU per infected cell. It demonstrated excellent environmental stability, maintaining over 80 % infectivity at temperatures up to 45 °C and across a broad pH range (4.0-10.0), indicating suitability for diverse aquaculture conditions. Genomic analysis confirmed the absence of virulence, antibiotic resistance, and lysogeny-associated genes, reinforcing its safety profile. Moreover, phage R32L not only lysed its original lethal pathogenic host but also showed cross-infectivity against two V. alginolyticus strains. It achieved the strongest bactericidal effect against V. parahaemolyticus vp-HL-202005, eliminating over 72 % of the bacterial population within 10 h, even at low concentrations. The high bacteriolytic efficiency may be related to certain host-specific factors in V. parahaemolyticus vp-HL-202005, such as capsular composition or limited intracellular defense. These findings underscore phage R32L as a promising biocontrol agent for phage therapy in aquaculture, particularly for the targeted prevention and control of HLVD outbreaks.