关键词: 西伯利亚鲟, 金黄杆菌, 药敏性, 侵染路径

Abstract: This paper screened the pathogen from the focus of Acipenser baerii, and combined with drug susceptibility test, infection path and analysis of host related indicators to understand the pathogenicity of the pathogen. In this study, by artificial regression infection test, a virulent strain B8 was isolated from the sick sturgeon, which had stronger pathogenicity to sturgeon, tilapia and zebrafish. This virulent strain B8 was identified as Chryseobacterium oncorhynchi by 16S rDNA gene sequence analysis. In addition, strain B8 had resistance to 10 routine antibiotics, and was highly sensitive to erythromycin and neomycin. The infection path showed B8 was firstly colonized in mucosal tissues (intestine and gills) then lymphoid tissues (liver, spleen and kidney). In all detected tissues, the highest numbers were obtained at 48 hpi, then gradually decreased. Moreover, significant up-regulation of IL-1β was found in intestine of sturgeon (peak value at 24 hpi), then gradually dropped down. Significant differences were appeared between 12~48 hpi compared to the unchallenged group (P<0.05). Furthermore, the antimicrobial response (lysozyme and ROS) showed notable up-regulation in the kindey of challenged sturgeon (peak value at 48 hpi). There were significant differences at 24～48 hpi compared to the unchallenged group (P<0.05). The results reported for the first time bath challenge virulent strain C. oncorhynchi B8 studies on its pathogenicity provided reference for prevention and treatment of diseases caused by Chryseobacterium of Acipenser baerii.

Key words: Acipenser baerii, Chryseobacterium, antibiotic susceptibility, infection path