Comparative Analysis of Super-Shedder Strains of Escherichia coli O157:H7 Reveals Distinctive Genomic Features and a Strongly Aggregative Adherent Phenotype on Bovine Rectoanal Junction Squamous Epithelial Cells
Comparative Analysis of Super-Shedder Strains of Escherichia coli O157:H7 Reveals Distinctive Genomic Features and a Strongly Aggregative Adherent Phenotype on Bovine Rectoanal Junction Squamous Epithelial Cells
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DOI：
10.1371/journal.pone.0116743
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发表时间：
2015-02-09
期刊：
影响因子：
3.7
通讯作者：
Kapur, Vivek
中科院分区：
文献类型：
--
作者：
Cote, Rebecca;Katani, Robab;Kapur, Vivek
产志贺毒素的大肠杆菌O157:H7 （O157）是一种重要的食源性病原体，对全世界的公共卫生构成严重威胁。O157的主要宿主是无症状的牛，其末端直肠-肛门交界处（RAJ）有该生物体。一些定植的动物，被称为“超级脱落者”（SS），已知会大量脱落O157 （100 - 104 CFU/g粪便）。最近的研究表明，SS牛在O157的流行和传播中起主要作用，但对与超级脱落相关的分子机制知之甚少。对SS O157菌株（SS17）进行全基因组序列分析，发现基因组全长5,523,849 bp，开放阅读框5,430个，质粒pO157和pSS17分别为94,645 bp和37,446 bp。比较分析显示，SS17与菠菜相关的O157爆发菌株聚集在一起，属于I/II谱系，进化枝8，D组和基因型1，这是O157的一个亚群，预测具有高毒力。与其他O157菌株（EC4115, EDL933, Sakai, TW14359）相比，SS17中发现了大量非同义snp和其他多态性，包括关键的粘附和毒力相关位点。表型分析显示，SS17在牛RAJ分层鳞状上皮（RSE）细胞上具有独特的、强粘附的聚集表型，在其他SS分离株中是保守的。SS17突变体的分子遗传和功能分析表明，SS分离株之间的强粘附聚集表型与lee无关，可能是一种新机制的结果。综上所述，我们的研究为研究SS相关的分子机制提供了一个合理的框架，并有力地证明SS O157分离株具有独特的特征，并且使用与lee无关的机制对牛直肠上皮细胞进行超粘附。
Shiga toxin-producing Escherichia coli O157:H7 (O157) are significant foodborne pathogens and pose a serious threat to public health worldwide. The major reservoirs of O157 are asymptomatic cattle which harbor the organism in the terminal recto-anal junction (RAJ). Some colonized animals, referred to as "super-shedders" (SS), are known to shed O157 in exceptionally large numbers (> 104 CFU/g of feces). Recent studies suggest that SS cattle play a major role in the prevalence and transmission of O157, but little is known about the molecular mechanisms associated with super-shedding. Whole genome sequence analysis of an SS O157 strain (SS17) revealed a genome of 5,523,849 bp chromosome with 5,430 open reading frames and two plasmids, pO157 and pSS17, of 94,645 bp and 37,446 bp, respectively. Comparative analyses showed that SS17 is clustered with spinach-associated O157 outbreak strains, and belongs to the lineage I/II, clade 8, D group, and genotype 1, a subgroup of O157 with predicted hyper-virulence. A large number of non-synonymous SNPs and other polymorphisms were identified in SS17 as compared with other O157 strains (EC4115, EDL933, Sakai, TW14359), including in key adherence-and virulence-related loci. Phenotypic analyses revealed a distinctive and strongly adherent aggregative phenotype of SS17 on bovine RAJ stratified squamous epithelial (RSE) cells that was conserved amongst other SS isolates. Molecular genetic and functional analyses of defined mutants of SS17 suggested that the strongly adherent aggregative phenotype amongst SS isolates is LEE-independent, and likely results from a novel mechanism. Taken together, our study provides a rational framework for investigating the molecular mechanisms associated with SS, and strong evidence that SS O157 isolates have distinctive features and use a LEE-independent mechanism for hyper-adherence to bovine rectal epithelial cells.