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为了解不同鱼源无乳链球菌(Streptococcus agalactiae)分子分型特征,分析菌株之间的相关性和同源性,本研究在采用S.agalactiae特异性cfb基因对分离菌株鉴定的基础上,对26株不同鱼源S.agalactiae进行了荚膜多糖血清型(CPS)多重PCR鉴定,同时采用多位点序列分型(MLST)和脉冲场凝胶电泳(PFGE)进行分子特征比较与同源性分析。结果显示,26株菌CPS型存在Ia(n=22)和III型(n=4)两种类型,其中黄河裸裂尻鱼源和罗非鱼源菌株均为Ia血清型,齐口裂腹鱼源菌株存在Ia(n=2)和III(n=4)型两种CPS型;多位点序列分型共得到3种STs序列型(ST-891、ST-103、ST-19),其中黄河裸裂尻鱼源和罗非鱼源菌株均为新的序列型ST-891,齐口裂腹鱼源菌株存在ST-103和ST-19两种STs型;PFGE聚类分析可分为16个PFGE谱型(A-P),其中优势带型为P型(n=9)。相同荚膜多糖血清型—MLST分型菌株在PFGE带型中呈现高度聚集。CPS分型与MLST分型、PFGE分型有很好的相关性,而CPS型、STs序列型、PFGE带型与宿主的来源没有明显的相关性。不同鱼源S.agalactiae分子特征的相似性,提示其存在交叉感染的可能性,而齐口裂腹鱼源S.agalactiae分子特征的多样性,提示其存在遗传变异的情况。
In order to understand the molecular typing characteristics of Streptococcus agalactiae in different fish sources and to analyze the correlation and homology among the strains, based on the identification of isolates from S.agalactiae-specific cfb gene, Twenty-six strains of S.agalactiae from different sources were identified by capsular polysaccharide serotype (CPS) multiplex PCR, and their molecular characteristics were compared with those by homology (MLST) and pulsed-field gel electrophoresis (PFGE) analysis. The results showed that there were two types of CPS in 26 isolates: type Ia (n = 22) and type III (n = 4) There were two CPS types of Ia (n = 2) and III (n = 4) in fish origin. Three STs sequences (ST-891, ST-103 and ST-19) The strains ST-89 and ST-90 were both ST-891 and ST-19, respectively. PFGE clustering analysis could be divided into 16 PFGE profiles (AP), of which the dominant band is P-type (n = 9). The same capsular polysaccharide serotype -MLST typing strains showed a high degree of aggregation in PFGE bands. There was a good correlation between CPS classification and MLST classification and PFGE classification. There was no significant correlation between CPS type, STs sequence type and PFGE type and host source. The similarity of the molecular characteristics of S.agalactiae in different fish suggests that there is a possibility of cross infection. However, the diversity of S.agalactiae molecular features in S. crassipes suggests that there is genetic variation.