一株北方地区鲟鱼源病原细菌金黄杆菌B8致病性研究

从西伯利亚鲟(Acipenser baerii)病灶处筛选病原菌,结合药敏性试验、侵染路径及宿主相关指标分析,以期了解该病原菌的致病性。通过人工回归感染试验,从病鱼肾脏部位分离得到1株病原菌B8,对鲟鱼、罗非鱼和斑马鱼均有较强的致病性。经16S rDNA序列分析鉴定为金黄杆菌,B8菌对庆大霉素和氯霉素等10种常用抗生素具有耐药性,对新霉素和红霉素敏感。侵染路径结果显示B8菌首先定殖在粘膜组织(鳃和肠),然后是淋巴组织(肝、脾和肾),各组织定殖菌量在48 hpi达到峰值,然后呈缓慢下降。肠道炎症因子IL-1β表达水平呈先上升(24 hpi为峰值)后下降趋势,在12～48 hpi间较未感染组差异显著(P0.05),头肾溶菌酶和ROS活性表现出类似趋势(48 hpi为峰值),在感染的24～48 hpi间较未感染组差异显著(P0.05)。首次报道了鲟鱼源致病株金黄杆菌,通过其致病性研究为西伯利亚鲟金黄杆菌引发的病害防控提供参考。

Pathogenicity Study of Chryseobacterium oncorhynchi B8 Isolated from Sturgeon (Acipenser baerii) in North China

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.