鲟分枝杆菌病及其病原研究

RESEARCH ON THE MYCOBACTERIOSIS AND ITS PATHOGEN IN STURGEONS

2009—2010年间,我国人工养殖的中华鲟(Acipenser sinensis)、史氏鲟(Acipenser schrencki)和杂交鲟(hybrid sturgeon:A.baeri-A.gueldenstaedtii)暴发了细菌性疾病。患病鲟通过组织切片观察,病原菌的分离、鉴定以及组织样品中病原菌的检测,结果显示从19条患病鲟中分离到49株分枝杆菌。病原菌经过多个保守基因的测序分析和部分生理生化特征的鉴定,共发现有7种分枝杆菌,分别为龟分枝杆菌(Mycobacterium chelonae)、海分枝杆菌(Mycobacterium marinum)、戈登氏分枝杆菌(Mycobacterium gordonae)、偶发分枝杆菌(Mycobacterium fortuitum)、苏尔加分枝杆菌(Mycobacterium szulgai)、猪分枝杆菌(Mycobacterium porcinum)和Mycobacterium arpuense。在诊断过程中发现两种或三种分枝杆菌同时存在于同一样品中,分子生物学的诊断结果表明分枝杆菌复合感染十分常见,而海分枝杆菌是分枝杆菌复合感染中最为常见的分枝杆菌。分离的病原菌对斑马鱼的攻毒试验结果表明在以上7种分枝杆菌中海分枝杆菌的毒力最强。以上结果表明海分枝杆菌是鲟分枝杆菌病的主要致病菌,分枝杆菌复合感染是鲟分枝杆菌病的主要感染形式。研究中史氏鲟和中华鲟的分枝杆菌病,以及在病鱼体内分离的猪分枝杆菌和M.arupense在国内外均尚未见报道。

Mycobacteriosis in fish is a common chronic progressive disease spread worldwide.Several outbreaks of mycobacteriosis in reared sturgeons occurred in China in year 2009 and 2010,which affected Chinese sturgeon（Acipenser sinensis）,Amur sturgeon（Acipenser schrencki） and hybrid sturgeon（Acipenser baeri-Acipenser gueldenstaedtii）.Mycobacteria were identified as the pathongens of this disease based on a variety of observation,including the identification of the isolates,the detection of pathogens in tissues,the clinical signs and the histopathological examinations.Forty-nine isolates of nontuberculous mycobacteria were extracted from 19 infected sturgeons.We identified seven species of Mycobacterium from these isolates,namely,Mycobacterium chelonae,Mycobacterium marinum,Mycobacterium gordonae,Mycobacterium fortuitum,Mycobacterium szulgai,Mycobacterium porcinum,and Mycobacterium arupense.We found that two or three mycobacterial species co-existed in the same tissues.Our results also showed that M.marinum was more prevalent than other mycobacterial species.Virulence assay revealed that M.marinum showed the highest pathogenicity to zebrafish.These results suggested that M.marinum should be the major pathogenic bacteria in sturgeon mycobacteriosis,and that the mixed mycobacterial infection be the predominant form of sturgeon mycobacteriosis.To our best knowledge,this is the first report about the mycobacteriosis in farmed Chinese sturgeons and Amur sturgeons,and is the first report about the isolation of M.porcinum and M.arupense from the infected fish.