Epidemiological investigation and whole genome of Vp AHPND CGVP22 isolated from an acute hepatopancreatic necrosis disease (AHPND) outbreak in Korea

AHPN disease, caused by Vibrio parahaemolyticus, poses a significant threat to global shrimp farming. Here, we investigated the epidemiological relationships of the AHPND- causing Vp _AHPND CGVP22, isolated from the 2016 AHPND outbreak in Pyeongtaek, Korea, through whole-genome sequencing (WGS). Initially, the presence of pir^AB genes was confirmed by PCR and nested PCR assays, which produced specific bands of 284 base pairs (bp) for pir^A and 392 bp for pir^B, and a 230 bp fragment in the AP4 nested PCR. The assembled whole-genome sequence of Vp _AHPND CGVP22 comprised of a total size of approximately 5.4 Mbp, consisting of 2 circular chromosomes (3.4 Mbp and 2.0 Mbp) and a 69 kbp plasmid. The RAST genome annotation identified 386 subsystems, including those related to virulence, motility, and iron acquisition. In silico multi-locus sequence typing (MLST) assigned Vp _AHPND CGVP22 to sequence type ST1166, and clustered with other ST1166 strains from Vietnam and China. Comparative genomic analysis revealed that Vp _AHPND CGVP22 exhibited 52 single nucleotide polymorphisms (SNPs) and 99.96 % average nucleotide identity (ANI) relative to the 13028/A3 strain, and 973 SNPs with 99.87 % ANI compared to the 20130629002S01 strain. The plasmid of Vp _AHPND CGVP22 showed 99.94 % nucleotide identity to the pVPA3-1 plasmid of the 13028/A3 strain, suggesting a close phylogenetic relationship. Furthermore, Vp _AHPND CGVP22 and 13028/A3 shared identical prophages (12B12), antibiotic resistance genes, and virulence factors, while other ST1166 strains exhibit distinct profiles. Collectively, these results provide valuable insights into the genomic and evolutionary relationships of Vp _AHPND CGVP22, contributing to a better understanding of the epidemiology of AHPN disease.