Complete genome sequence of Vibrio diabolicus bacteriophage vB_Vc_SrVc2 and its efficacy as prophylactic phage therapy.

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Vibrio diabolicus is widely distributed in the marine environment and is an important pathogen of aquatic organisms such as shrimp, fish, and mollusks. The emergence of multi-drug resistance among these bacteria has resulted in a global public health problem, which requires alternative treatment approaches, such as phage therapy. In the present study, we isolated the phage vB_Vc_SrVc2 from the hepatopancreas of white shrimp showing symptoms of acute hepatopancreatic necrosis disease (AHPND) and evaluated the efficacy of this phage in preventing the mortality associated with V. diabolicus presence in shrimp culture. Phage vB_Vc_SrVc2 belongs to the genus Maculvirus within the family Autographiviridae and demonstrates high lytic ability against Vibrio isolates. It exhibits substantial resilience across a broad range of temperatures, salinity levels, UV radiation and chloroform exposure. The phage genome size is 43,157 bp, with a GC content of 49.2%, that encodes 49 putative ORFs, and no tRNAs. Compared to phage vB_Vc_SrVc9, it shows three single nucleotide polymorphisms, two small deletions, and one nucleotide insertion, which result in slightly different infectivity profiles. No lysogeny-related genes were detected in the vB_Vc_SrVc2 genome. In vivo trials revealed that the phage offered protection against V. diabolicus infection by delaying mortality onset by at least 40 hours post-infection (hpi). Although phage vB_Vc_SrVc2 alone significantly reduced mortality associated with V. diabolicus infection, this capacity could be enhanced with multiple doses and/or the use of phage cocktails or probiotics. Overall, phage vB_Vc_SrVc2 shows promising potential for therapeutic application in the aquaculture industry against V. diabolicus infections.