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目的分析肠致病性大肠埃希菌(EPEC)致病岛(PAIs)基因进化特点。方法 EPEC Deng分离自我国婴幼儿腹泻患者粪便标本,鉴定该菌株血清型并进行药敏试验;采用Illumina 2000仪器对菌株进行全基因序列测序,PHAST软件定位菌株原噬菌体(prophages,PPs)在染色体中的位置,MUMmer软件进行共线性分析,构建系统发育树,了解同源基因进化规律。应用PAI_finder软件对基因组进行PAIs预测,了解PAIs核心区域(LEE)和核心基因同源进化规律,并进行遗传多态性分析。结果 EPEC Deng菌株归属O119∶H6,药敏结果显示该菌株对环丙沙星、左氧氟沙星及氨苄西林耐药,对其余的抗菌药物均敏感。基因组(染色体)序列大小为5 025 482 bp(GC含量为50.52%),质粒序列大小为207 564 bp(GC含量为49.50%)。共找到17个PPs,系统发育树分析发现,EPEC Deng株基因组与O26∶H11、O111∶H同源性较高;EPEC Deng株PAIs和核心基因均与RDEC-1和O26∶H413/89-1株具有高同源性;遗传多样性分析结果显示,紧密素(eae)及其受体(tir)多态性丰富,π值均>0.10,Ⅲ型分泌系统(TTSS)分泌蛋白相对稳定。结论此研究明确了EPEC Deng株基因组及PAIs的进化特点,有助于了解了本土分离的EPEC基因特点。
Objective To analyze the evolutionary characteristics of PAIs in enteropathogenic Escherichia coli (EPEC). Methods EPEC Deng was isolated from stool samples from infants and young children with diarrhea in our country. The serotype of EPEC Deng was identified and susceptibility test was performed. Whole genome sequence was sequenced using Illumina 2000 instrument. PHAST software was used to locate the prophages (PPs) MUMmer software was used for collinearity analysis to construct phylogenetic tree and to understand the evolution law of homologous genes. Using PAI_finder software to predict the PAIs of the genome, the homologous evolution rules of core region (LEE) and core gene of PAIs were studied and the genetic polymorphism was analyzed. Results The strain EPEC Deng was attributed to O119: H6. The results of drug sensitivity showed that the strain was resistant to ciprofloxacin, levofloxacin and ampicillin, and sensitive to the rest antibiotics. The size of the genome (chromosome) was 5 025 482 bp (GC content was 50.52%) and the size of the plasmid was 207 564 bp (GC content was 49.50%). A total of 17 PPs were found. Phylogenetic tree analysis showed that EPEC Deng strain was highly homologous to O26:H11 and O111:H genes. The PAIs and core genes of EPEC strain Deng were highly homologous to RDEC-1 and O26: H413 / 89-1 The results of genetic diversity analysis showed that eae and its receptor (tir) were rich in polymorphisms, both of which were all> 0.10. The secreted proteins of type Ⅲ secretion system (TTSS) were relatively stable. Conclusion This study identified the evolutionary characteristics of EPEC strain Dengjunxia and PAIs and helped to understand the characteristics of EPEC isolated locally.