Department of Food Safety, Nutrition and Veterinary Public Health, Istituto Superiore di Sanità, Rome, Italy.
Department of Biology and Biotechnology "Charles Darwin", Università Sapienza di Roma, Rome, Italy.
Front Cell Infect Microbiol. 2020 Jun 3;10:260. doi: 10.3389/fcimb.2020.00260. eCollection 2020.
Enteroinvasive (EIEC) cause intestinal illness through the same pathogenic mechanism used by spp. The latter species can be typed through genomic and phenotypic methods used for and have been proposed for reclassification within species. Recently the first appearance of a highly pathogenic EIEC O96:H19 was described in Europe as the causative agent of two large outbreaks that occurred in Italy and in the United Kingdom. In contrast to spp and to the majority of EIEC strains, EIEC O96:H19 fermented lactose, lacked pathoadaptive mutations, and showed good fitness in extracellular environment, similarly to non-pathogenic , suggesting they have emerged following acquisition of the invasion plasmid by a non-pathogenic . Here we describe the whole genome comparison of two EIEC O96:H19 strains isolated from severe cases of diarrhea in Uruguay in 2014 with the sequences of EIEC O96:H19 available in the public domain. The phylogenetic comparison grouped all the O96:H19 strains in a single cluster, while reference EIEC strains branched into different clades with strains occupying apical positions. The comparison of the virulence plasmids showed the presence of a complete conjugation region in at least one O96:H19 EIEC. Reverse Transcriptase Real Time PCR experiments confirmed in this strain the expression of the pilin-encoding gene and conjugation experiments suggested its ability to mobilize an accessory plasmid in a recipient strain. Noteworthy, the region was comprised between two reversely oriented IS elements, which were also found as remnants in another EIEC O96:H19 plasmid lacking the . We hypothesize that an IS-mediated recombination mechanism may have caused the loss of the conjugation region commonly observed in EIEC and virulence plasmids. The results of this study support the hypothesis of EIEC originating from non-pathogenic through the acquisition of the virulence plasmid via conjugation. Remarkably, this study showed the ability of a circulating EIEC strain to mobilize plasmids through conjugation, suggesting a mechanism for the emergence of novel EIEC clones.
肠侵袭性大肠杆菌（EIEC）通过与 spp 相同的致病机制引起肠道疾病。后者可以通过用于 和 的基因组和表型方法进行分型，并已被提议重新分类为 种内。最近，在欧洲首次出现了一种高度致病性的 EIEC O96:H19，它是意大利和英国发生的两次大规模暴发的病原体。与 spp 和大多数 EIEC 菌株不同，EIEC O96:H19 发酵乳糖，缺乏适应病变的突变，并在细胞外环境中表现出良好的适应性，类似于非致病性 ，这表明它们是在非致病性 获得侵袭质粒后出现的。在这里，我们描述了 2014 年乌拉圭严重腹泻病例中分离的两株 EIEC O96:H19 菌株与公共数据库中可用的 EIEC O96:H19 序列的全基因组比较。系统发育比较将所有 O96:H19 菌株分为一个单独的簇，而参考 EIEC 菌株分为不同的分支， 菌株占据顶端位置。毒力质粒的比较显示，至少有一株 O96:H19 EIEC 中存在完整的接合区。逆转录实时 PCR 实验证实该菌株表达了菌毛编码基因，接合实验表明其能够在受体菌株中移动辅助质粒。值得注意的是， 区位于两个反向取向的 IS 元件之间，这两个元件也作为另一个缺乏 的 O96:H19 质粒的残余物存在。我们假设，IS 介导的重组机制可能导致 EIEC 和 毒力质粒中常见的接合区缺失。本研究结果支持 EIEC 起源于非致病性 通过接合获得毒力质粒的假说。值得注意的是，本研究表明了一种循环 EIEC 菌株通过接合转移质粒的能力，这表明了新的 EIEC 克隆出现的一种机制。
