鱼源无乳链球菌的血清型及分子分型研究

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, 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。

SEROTYPES AND MOLECULAR TYPING OF STREPTOCOCCUS AGALACTIAE ISOLATED FROM FISH

To analyze molecular typing characteristics ofStreptococcus agalactiae isolated from different fish sources and understand the correlation and homology between the strains, this study identified capsular polysaccharide sero-type (CPS) with multiplex PCR for 26S. agalactiae. Multilocus sequence typing (MLST) and pulsed field gel electro-phoresis (PFGE) were adopted to study the molecular characteristics and homology based on the specificcfb gene ofS. agalactiae. The results showed that CPS type had Ia (n=22) and III (n=4) two types, of whichS. agalactiae isolated fromSchizopygopsis pylzovi and tilapia were Ia, andS. agalactiae isolated fromSchizothorax prenati existed Ia (n=2) and III (n=4) two types. Multilocus sequence typing received three STs sequence types (ST-891、ST-103、ST-19), among which the sequence types ofS. agalactiae isolated fromSchizopygopsis pylzovi and tilapia were new sequence type ST-891, andS. agalactiae isolated fromSchizothorax prenati existed ST-19 and ST-103 two sequence types. PFGE cluster analysis created 16 banding patterns (A-P), and the cluster P was the preponderant type. Similar capsular polysaccharide serotype-MLST type strains presented high concentration in the PFGE type. CPS types, MLST types and PFGE types were correlated, but CPS types, STs sequence types and PFGE banding types had no obvious correla-tion with the host's sources. The similarity of molecular characteristics ofS. agalactiae isolated from different fish sources suggests the possibility of cross infection, and the diversity of molecular characteristics ofSchizothorax prenati suggest the existence of heritable variation.