罗非鱼无乳链球菌的分子鉴定

Molecular Classification of Isolated Streptococcus agalaciate from Tilapia

对罗非鱼致病菌株TL60829NA及其人工感染后分离菌株TL60829NA1、TL60829NA2应用原核生物16S rRNA基因通用引物进行分子分类学鉴定。对这些菌株进行16srRNA基因的克隆、序列分析,核酸序列同源性分析表明,TL60829NA及其人工感染后分离菌株TL60829NA1、TL60829NA2为同一种细菌。其中,TL60829NA2与GenBank登陆号为DQ303183的无乳链球菌(Streptococcus agalaciate)菌株ATCC13813序列同源性最高(99.8%)。同时,通过与常引起罗非鱼链球菌病的S.agalaciate、S.iniae代表菌株16srRNA基因构建的发育进化树表明,该菌株及其人工感染后分离菌株与S.agalaciate代表菌株构成一个进化分枝,而4株S.iniae代表菌株的16srRNA基因则构成另一个分枝。本研究证实了从发病罗非鱼肝脏组织中分离到的致病性链球菌为无乳链球菌。

One strain of bacteria TL60829NA was isolated from the outbreak epidemical diseased tilapia,TL60829NA1 was isolated from the diseased tilapia challenged with TL60829NA by muscle injection,and TL60829NA2 from the diseased tilapia challenged with TL60829NA1.16s rRNA gene partial sequences were conduced to identify the pathogenic three strains.Phylogenetic analysis based on 16s rRNA gene sequences indicated that homology of TL60829NA,TL60829NA1 and TL60829NA2 showed high levels of similarity to Streptococcus agalaciate,and the similarity was 99.8%.The phylogenetic tree of Streptococcus spp.showed that these three isolates clustered together with Streptococcus agalaciate,the S.iniae strains clustered together.Based on these results,the isolated strain TL60829NA is Streptococcus agalaciate,and so do the TL60829NA1 and TL60829NA2.