Hybrid Shiga Toxin-Producing and Enterotoxigenic Escherichia sp Cryptic Lineage 1 Strain 7v Harbors a Hybrid Plasmid
Hybrid Shiga Toxin-Producing and Enterotoxigenic Escherichia sp Cryptic Lineage 1 Strain 7v Harbors a Hybrid Plasmid
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DOI：
10.1128/aem.01129-16
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发表时间：
2016-07-01
影响因子：
4.4
通讯作者：
Lacher, David W.
中科院分区：
文献类型：
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作者：
Leonard, Susan R.;Mammel, Mark K.;Lacher, David W.
产生志贺毒素的大肠杆菌(STEC)和产肠毒素的大肠杆菌(ETEC)的混合分离株编码耐热肠毒素(ST)的频率越来越高。然而，关于这些菌株所含的质粒的信息很少。在本研究中，我们对来自STEC/ETEC杂交菌7v的一个质粒p7v进行了测序和鉴定。STEC/ETEC杂交株和其他致病类型的原型菌株的全基因组系统发育分析。神秘血统1(CL1)分支。P7v的全长为229,275bp，编码STEC和ETEC质粒上通常携带的假定毒力因子，表明该菌株的杂交性质不仅仅是编码这两种毒素。质粒p7v携带两个具有相同序列的sta拷贝，它们与在原型人ETEC株中发现的sta序列不同。使用基于从STA和STB序列构建的系统发育的命名方案，在p7v上编码的STA被命名为STA4。在计算机分析中确定，p7v还编码K88菌毛，这是一种通常与猪ETEC质粒有关的定植因子。P7v序列和质粒编码的毒力因子的存在与其他STEC/ETEC CL1杂交基因组进行了比较，揭示了菌株水平的基因获取/丢失。此外，对24个STEC/ETEC杂交基因组的询问以确定质粒复制子、定植因子、STX和ST亚型以及其他质粒编码的毒力基因，突出了这些杂交菌株的多样性。从环境、动物和人类临床样本中分离的产生志贺毒素的大肠杆菌/产肠毒素大肠杆菌(STEC/ETEC)菌株可能是一个新的威胁，作为食源性病原体。这些菌株的特征对于评估毒力潜力、帮助开发病原体检测方法以及了解杂交菌株如何进化可能对公共健康产生更大影响非常重要。据我们所知，这项研究既是对STEC/ETEC杂交株闭合质粒序列的首次表征，也是迄今为止对现有STEC/ETEC杂交株基因组进行的最全面的系统发育分析。结果表明，质粒相关毒力基因的迁移性如何导致在STEC/ETEC杂交菌株中创建不同的质粒库。
Hybrid isolates of Shiga toxin-producing Escherichia coli (STEC) and enterotoxigenic E. coli (ETEC) encoding heat-stable enterotoxin (ST) are being reported with increasing frequency from a variety of sources. However, information regarding the plasmids that these strains harbor is scarce. In this study, we sequence and characterize a plasmid, p7v, from the STEC/ETEC hybrid strain 7v. Whole-genome phylogenetic analyses of STEC/ETEC hybrid strains and prototype E. coli isolates of other pathotypes placed 7v in the Escherichia sp. cryptic lineage 1 (CL1) clade. The complete plasmid, p7v, was determined to be 229,275 bp and encodes putative virulence factors that are typically carried on STEC plasmids as well as those often carried on ETEC plasmids, indicating that the hybrid nature of the strain extends beyond merely encoding the two toxins. Plasmid p7v carries two copies of sta with identical sequences, which were discovered to be divergent from the sta sequences found in the prototype human ETEC strains. Using a nomenclature scheme based on a phylogeny constructed from sta and stb sequences, the sta encoded on p7v is designated STa4. In silico analysis determined that p7v also encodes the K88 fimbria, a colonization factor usually associated with porcine ETEC plasmids. The p7v sequence and the presence of plasmid-encoded virulence factors are compared to those of other STEC/ETEC CL1 hybrid genomes and reveal gene acquisition/loss at the strain level. In addition, the interrogation of 24 STEC/ETEC hybrid genomes for identification of plasmid replicons, colonization factors, Stx and ST subtypes, and other plasmid- encoded virulence genes highlights the diversity of these hybrid strains.IMPORTANCEHybrid Shiga toxin-producing Escherichia coli/enterotoxigenic Escherichia coli (STEC/ETEC) strains, which have been isolated from environmental, animal, and human clinical samples, may represent an emerging threat as food-borne pathogens. Characterization of these strains is important for assessing virulence potential, aiding in the development of pathogen detection methods, and understanding how the hybrid strains evolve to potentially have a greater impact on public health. This study represents, to our knowledge, both the first characterization of a closed plasmid sequence from a STEC/ETEC hybrid strain and the most comprehensive phylogenetic analysis of available STEC/ETEC hybrid genomes to date. The results demonstrate how the mobility of plasmid-associated virulence genes has resulted in the creation of a diverse plasmid repertoire within the STEC/ ETEC hybrid strains.