First Report of Elizabethkingia miricola Isolated from Low-Salinity-Cultured River Puffer (Takifugu obscurus) in South Korea

This study reports the first isolation of Elizabethkingia miricola from cultured river puffer (Takifugu obscurus) in South Korea under low-salinity aquaculture conditions. A total of 5000 juvenile T. obscurus were reared for 20 months in a recirculating aquaculture system with salinity maintained at 3–5 ppt. During the rearing period, fish exhibited a cumulative mortality rate of 58.17%, presenting clinical signs such as lethargy, fin rot, hepatic hemorrhage, and white nodules in the spleen and kidney. Biochemical and molecular analyses identified E. miricola in the internal organs of diseased fish. All isolates exhibited multidrug resistance and showed 98.8–99.8% 16S rRNA gene sequence similarity to E. miricola, forming a distinct phylogenetic cluster. Additionally, several virulence-associated genes (fabG, fabV, wecB, ureB, aceA, acyl) were detected in the isolates. Histopathological examination revealed granulomatous lesions in multiple organs, including the gill, heart, kidney, and spleen. This study represents the first report of E. miricola isolated from cultured river puffer in South Korea and suggests its potential association with disease in this species, as well as its possible zoonotic relevance. These findings highlight the importance of disease monitoring and pathogen surveillance in low-salinity aquaculture systems.