72株大肠埃希菌参考菌株的基因组分型及种系发育关系

Genomic typing and phylogenetic analysis of 72 Escherich coli reference strains

目的通过两种分子生物学分型方法对72株分离自不同地域不同宿主的大肠埃希菌进行分型以及种系进化研究,并比较两种方法的差异。方法利用72株大肠埃希菌的7个持家基因序列进行多位点序列分型;培养大肠埃希菌,用I-CeuI酶切全基因组DNA以及用脉冲场凝胶电泳分离DNA片段后,根据酶切图谱的异同进行脉冲场凝胶电泳分型。结果这些菌株根据多位点序列分型可以分为49个型,而通过I-CeuI酶切条带差异可以分为68个型,二者有一定程度的重叠。结论脉冲场凝胶电泳分型的分辨率更高,并且72株大肠埃希菌的基因序列以及基因组结构都存在多样性。

Objective To study the molecular typing and phylogenetic evolution of 72 Escherichia coli （E. coli ） reference collection （ECOR） from different areas and hosts by different molecular typing methods. Methods Sequences of the seven housekeeping genes were downloaded from multilocus sequence typing （MLST） database and the phylogenetic tree was constructed by MEGA 4.0 program based these sequence alignment file; 72 E. coli strains were digested by endonuclease I-CeuI and separated by pulsed-field gel eleetrophoresis, then E. coli strains were typed by the difference of fragments size and location. Results Seventy-two E. coli strains were identified into 49 sequence types and clustered into 7 clonal complexes and 29 singletons by MLST method. These strains were identified into 68 distinct types by similarity fragments size of PFGE results. From both methods, the genetic relationship of strains in the same pattern types were very closely in MLST phylogenetic tree. Conclusion The discrimina- tory abilities of PFGE is higher than MLST, and there is significant diversity in genome sequence and structure among the 72 E. coli isolates.