Vibrio Phage VPK8 Offers New Hope Against Seafood Pathogens

In a new study published in the Virology Journal (2025), researchers introduce Vibrio phage VPK8, a lytic phage isolated from blood cockles. The study dives into Vibrio phage VPK8's host range, genomic features, and infection dynamics, making a strong case for its use in both food safety and aquacultural biocontrol strategies.

Vibrio parahaemolyticus is a Gram-negative bacterium that causes seafood-associated gastrointestinal illness in humans and acute hepatopancreatic necrosis disease (AHPND) in shrimp. AHPND is a condition responsible for mass mortality of seafood and heavy economic losses since 2009. Traditional control strategies that rely on antibiotics have led to increased resistance and environmental concerns.

This study identifies and analyzes Vibrio phage VPK8, a lytic virus capable of infecting Vibrio parahaemolyticus and select strains from four other Vibrio species, including those isolated from clinical cases and seafood sources. These results support the potential use of phages like Vibrio phage VPK8 as promising biocontrol agents due to their host specificity and potent bacteriolytic activity.

Experimental Workflow and Key Findings

The phage was first isolated from fresh blood cockles using the double-layer method. The next step was to determine which Vibrio species the phage could attack. This included conducting host range testing on seafood, clinical, and shrimp disease-associated (VpAHPND) isolates using spot assays. The results indicated that VPK8 successfully lysed:

• 64% of AHPND-associated V. parahaemolyticus strains
• 58% of clinical strains
• 53% of seafood strains

Efficiency of plating (EOP) analysis was performed to determine the infection productivity of VPK8. Results revealed that nine bacterial strains showed high susceptibility to Vibrio phage VPK8, indicating strong productive infection. However, it showed no effective infection in any V. parahaemolyticus strain associated with AHPND or in V. campbellii, highlighting its limited activity against these particular groups. The morphology of the phage was examined using TEM, which revealed that the phage has characteristics consistent with other members of the Autographiviridae, including an icosahedral head and a short tail.

Genomic Insights from Phage VPK8

For genome isolation and purification, the researchers used Norgen's Phage DNA Isolation Kit to ensure the isolation of clean, high-quality DNA for sequencing. This workflow supports detailed genomic characterization and ensures reproducibility in phage discovery.

Whole-genome sequencing showed that VPK8 is a member of the Autographiviridae family with a linear 42.8 kb dsDNA genome. The genome comprises 48 coding sequences, including several responsible for its lytic capabilities. Phylogenetic analysis shows VPK8 is most closely related to Vibrio phage vB_VpaP_MGD1 but with key genetic differences, indicating evolutionary divergence.

Conclusion and Relevance for Phage Therapy

VPK8 presents as a potent lytic bacteriophage with broad activity against Vibrio parahaemolyticus strains from both clinical and seafood sources. Its fast replication cycle, clear safety profile, and effective suppression of bacterial growth make it an attractive candidate for bacteriophage research and applied phage therapy.

As global interest in phage therapy and antibiotic alternatives grows, VPK8 offers new hope for controlling seafood-borne pathogens and improving aquaculture biosecurity.

📄 Read the Full Research Study: Characterization and genome analysis of lytic Vibrio phage VPK8