Pathogenicity and detection method based on interferon release assay of Mycobacteria marinum isolated from sturgeon

Abstract

Mycobacterium marinum is an opportunistic pathogen and can infect marine and freshwater fish. In this study, an acid-fast bacillus strain was isolated from the moribund Acipenser sinensis and identified as M. marinum via specific plate culture and phylogenetic analysis of 16S rRNA. M. marinum exhibited pathogenicity in Chinese sturgeon and hybrid sturgeon (A. schrenckii ♀ × A. baerii ♂). The histopathology results showed that granulomatous nodules were observed in the liver, spleen and kidney of the Chinese sturgeon after M. marinum infection. Nuclear necrosis and large production of hemosiderin appeared in the liver. The medullary structure of the spleen was disordered. The glomerulus was deformed and disintegrated, and the glomerular lumen was dilated in the kidney. The expressions of IFN-e1, IFN-γ, TNFα1, TNFα2, IL-1β, and IL-6 of Chinese sturgeon were significantly upregulated by M. marinum in vivo and in vitro. The whole blood ELISA detection method was constructed by IFN-γ polyclonal antibody. The infection of M. marinum in hybrid sturgeon could be judged by detecting the concentration of IFN-γ in plasma. In summary, M. marinum has a strong pathogenicity to sturgeon and could induce the immune response of the host. The sturgeon IFN-γ-ELISA detection method was expected to become a tool for diagnosing M. marinum infection in sturgeon. This study could provide the scientific basis for effectively controlling and reducing the pathogenic M. marinum disease of sturgeon in aquaculture.