Cote Rebecca, Katani Robab, Moreau Matthew R, Kudva Indira T, Arthur Terrance M, DebRoy Chitrita, Mwangi Michael M, Albert Istvan, Raygoza Garay Juan Antonio, Li Lingling, Brandl Maria T, Carter Michelle Q, Kapur Vivek
Department of Veterinary and Biomedical Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America; The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
Department of Veterinary and Biomedical Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
PLoS One. 2015 Feb 9;10(2):e0116743. doi: 10.1371/journal.pone.0116743. eCollection 2015.
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.
产志贺毒素大肠杆菌O157:H7（O157）是重要的食源性病原体，对全球公共卫生构成严重威胁。O157的主要宿主是无症状牛，它们在直肠肛门末端连接处（RAJ）携带该病原体。一些被定植的动物，被称为“超级排菌者”（SS），已知会大量排出O157（>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，但关于超级排菌相关的分子机制知之甚少。对一株SS O157菌株（SS17）的全基因组序列分析显示，其染色体基因组为5,523,849 bp，有5,430个开放阅读框，还有两个质粒，分别为94,645 bp的pO157和37,446 bp的pSS17。比较分析表明，SS17与菠菜相关的O157暴发菌株聚类，属于I/II谱系、8分支、D组和基因型1，是具有预测高毒力的O157亚组。与其他O157菌株（EC4115、EDL933、Sakai、TW14359）相比，在SS17中鉴定出大量非同义单核苷酸多态性和其他多态性，包括关键的黏附相关和毒力相关位点。表型分析揭示了SS17在牛RAJ分层鳞状上皮（RSE）细胞上具有独特且强黏附的聚集表型，在其他SS分离株中也保守存在。对SS17特定突变体的分子遗传和功能分析表明，SS分离株中的强黏附聚集表型不依赖于LEE，可能源于一种新机制。综上所述，我们的研究为研究与SS相关的分子机制提供了合理框架，并有力证明SS O157分离株具有独特特征，且使用不依赖于LEE的机制高度黏附于牛直肠上皮细胞。
