First Report and Pathogenicity of Vibrio campbellii (VCAHPND) Isolated in South Korea

The global shrimp farming industry is impacted by various infectious diseases, leading to marked production losses. Virulent Vibrio parahaemolyticus strains (VPAHPND) and other Vibrio species cause acute hepatopancreatic necrosis disease (AHPND) in shrimp. We isolated a binary toxin PirA/B-bearing V. campbellii strain (HJ-2023) from a Korean shrimp farm. The biochemical characteristics and antibiotic susceptibility of HJ-2023 were analyzed and compared to those of PirA/B-bearing VPAHPND. Non-AHPND-causing V. campbellii was the control. The pathogenicity of each strain was analyzed in white-leg shrimp. Phylogenetic analysis classified the isolated HJ-2023 strain as V. campbellii. Biochemical tests confirmed distinct properties of HJ-2023, compared to the genetically similar V. harveyi group. The AHPND-causing toxin gene of HJ-2023 showed 100% similarity to the rpoD gene of VCAHPND. An antibiotic disc susceptibility test indicated that HJ-2023 showed resistance to ampicillin, clindamycin, lincomycin, and erythromycin, which is effective against gram-positive bacteria, and showed weak sensitivity to gentamycin. Furthermore, HJ-2023 was 25% less toxic than VPAHPND but could be lethal during aquaculture-related outbreaks. These results highlight the complexity and virulence of AHPND-causing strains through multiple pathways and confirm the pathogenicity of V. campbellii, which increases the risk posed by AHPND to shrimp aquaculture. Our findings could help prevent AHPND.