我国华南地区罗非鱼源无乳链球菌分子流行病学研究

Molecular Epidemiology of Pathogen Streptococcus agalactiae from Tilapia in Southern China

为了解我国3个地区(广东省、广西省和海南省)罗非鱼源无乳链球菌临床株的遗传背景及进化关系,对2010—2011年间采集分离的128株链球菌,采用Bio-MerieuxVITEK进行生理生化分析和16SrRNA法鉴定菌株类型,并运用多位点序列分型技术,确定其等位基因谱型及菌株序列型。试验结果表明,通过对分离菌株的生理生化及16SrRNA基因进行分析,确认有104株为无乳链球菌,这104株分属1个已知克隆系ST-7和2个未知克隆系NST-1和NST-2,其中NST-1克隆系所占比列最多,占88.5%(92/104)。本研究结果揭示了我国南方3个地区无乳链球菌分离株呈多克隆系并存,以新型NST-1克隆系为主,应加强对新克隆系的病原学监测。应用MLST分子分型技术,初步揭示了我国南方3个地区罗非鱼源无乳链球菌的遗传进化关系。

Identification was carried out in 128 strains of Streptococcus isolated from tilapia in southern China （Guangdong, Guangxi and Hainan provinces） from 2010 to 2011 by Bio-MerieuxViTEK and 16S rRNA sequence analysis and 7 housekeeping genes were seguenced in 104 strains of S. agalactiae by Mul- tilocus Sequence Typing （MLST） technique to evaluate the genetic diversity of S. agalactiae. Results were analyzed and compared with sequence information in PubMLST databases to determine a strain allelic profile and assigned a sequence type （ST）. It was found that total 104 strains were within 3 clone se- quences. ST-7 and 2 types of unidentified NST-1 and NST-2, NST-1 having the maximal proportion of 88.5% （92/104）. It was revealed that there were multiple clonal sequences of S. agalactiae isolate from tilapia in southern China with high pathogenetic and prevalent. It is suggested that S. agalactiae isolate from tilapia be intense surveillance efforts. The findings indicate that MLST technique is an ideal tool to reveal genetic evolution profile of S. agalactiae isolated from tilapia in southern China.