论文部分内容阅读
为了解2009-2010年间在河南、甘肃地区分离鉴定的5株大肠埃希菌O157(E.coli O157)携带stx的情况及不同分离株间stx分子进化与变迁的情况,本研究利用PCR方法对分离株进行了stx基因检测,并完成了序列测定与系统演化分析。结果表明,5株不同动物源的分离株均含有stx1及stx2基因。序列分析结果显示5株分离株间stx1、stx2的核苷酸及氨基酸同源性均较高;stx1基因均与参考株中的山羊源和食品源E.coli O157菌株的同源性较高,进化树中遗传距离最近;分离株的stx2基因与多株牛源及少数人源参考株也具有较高的同源性,进化树中虽然5株分离菌均在一个大主干分支中,但分离株27与其他各分离株及参照株遗传距离最远,独自处于一次级分支中;分离株L37与W、12与50分别分布于牛源、人源E.coli O157小次级分支中;由此可推测,分离株所携带的stx1很有可能是经食品源或羊源E.coli O157传递而来;分离株L37与W、分离株12与50的stx2可能是由牛源、人源E.coli O157菌株传递而来,分离株27的stx2来源不清楚。研究结果表明,5株E.coli O157分离株均含有stx1、stx2基因,但两个基因的起源存在差异。
In order to understand the situation of stx in five isolates of Escherichia coli O157 (E. coli O157) isolated in Henan and Gansu from 2009 to 2010 and the evolution and evolution of stx between different isolates, Stx gene was tested in the isolates, and sequence analysis and phylogenetic analysis were completed. The results showed that the five isolates from different animal origins contained stx1 and stx2 genes. Sequence analysis showed that the nucleotide and amino acid homology of stx1 and stx2 were higher among the five isolates. The stx1 gene shared high homology with goat source and food source strain E. coli O157 in the reference strain, The genetic distance in the phylogenetic tree was the closest. The stx2 gene of the isolate also had high homology with many bovine and few human reference strains. Although 5 isolates were in one large main branch in the phylogenetic tree, Strain 27 and other isolates and reference strains of the most distant genetic distance, alone in a secondary branch; isolate L37 and W, 12 and 50 were distributed in bovine, human E. coli O157 small secondary branches; from It can be inferred that the stx1 carried by the isolate is likely to be passed from food source or goat E. coli O157. Stx2 of isolates L37 and W and isolates 12 and 50 may be derived from bovine, human E The passage of stx2 from isolate 27 was unclear. The results showed that five isolates of E. coli O157 contain stx1 and stx2 genes, but the origin of the two genes is different.