为进一步阐明不同宿主不同地区无乳链球菌之间的关系，本研究从细菌形态学、生理生化、16S rRNA和cfb基因等方面，鉴定了2009—2011年广东、海南等地区的25株罗非鱼链球菌病原。同时结合全球不同宿主来源的84株链球菌16S rRNA基因序列，利用Modeltest 3.7、MEGA 3.0、MrBayes 3.0 b4 进行综合系统发育分析。结果表明：2009—2011年罗非鱼链球菌病原均为无乳链球菌且它们在进化上聚为一个支系，说明2009—2011年广东、海南等地区罗非鱼无乳链球菌病原具有相同的起源。此外，罗非鱼无乳链球菌与法国人源、美国人源、牛源以及日本猪源等无乳链球菌均以高支持率(100)聚在一个支系，说明全球不同宿主来源的无乳链球菌亦具有相同的进化起源，同时也证明了中国罗非鱼无乳链球菌的潜在人畜共患性，这是国内首次对不同宿主无乳链球菌进行系统发育研究。

In order to explore the relationship among S. agalactiae from different area and host, this study had identified 25 Streptococcus isolates based on bacterial morphology, physiological and biochemical property, 16S rRNA and cfb genes, which from tilapia farmed in Guangdong and Hainan Province in 2009—2011. Meanwhile, by use of Modeltest 3.7, MEGA 3.0, MrBayes 3.0 b4, the 25 Streptococcus spp. had been carried out phylogenetic analyses with other 84 S. agalactiae isolates from different sources based on the 16S rRNA genes. The results showed that the causative agents of Streptococcicosis from tilapia of Guangdong, Hainan in 2009—2011 were S. agalactiae, which were classified into one group in phylogenetic analyses. These revealed that tilapia S. agalactiae isolates from Guangdong and Hainan in 2009—2011 have the same evolutionary origin. In addition, S. agalactiae from tilapia farmed in China, from Human of France and America, from cattle and swine of Japan were all clustered into one group with high bootstrap. Theses inferred that S. agalactiae isolates from different area and host had the same evolutionary origin, which also illustrated S. agalactiae from tilapia of China had potential zoonotic capacity. This was firstly to explore the phylogenetic relationship of S. agalactiae from varied source in China.