Wernigerode Branch, Robert Koch Institute, Wernigerode, Germany.
PLoS One. 2011 Apr 29;6(4):e16720. doi: 10.1371/journal.pone.0016720.
Enterococci are the third leading cause of hospital associated infections and have gained increased importance due to their fast adaptation to the clinical environment by acquisition of antibiotic resistance and pathogenicity traits. Enterococcus faecalis harbours a pathogenicity island (PAI) of 153 kb containing several virulence factors including the enterococcal surface protein (esp). Until now only internal fragments of the PAI or larger chromosomal regions containing it have been transferred. Here we demonstrate precise excision, circularization and horizontal transfer of the entire PAI element from the chromosome of E. faecalis strain UW3114. This PAI (ca. 200 kb) contained some deletions and insertions as compared to the PAI of the reference strain MMH594, transferred precisely and integrated site-specifically into the chromosome of E. faecalis (intergenic region) and Enterococcus faecium (tRNAlys). The internal PAI structure was maintained after transfer. We assessed phenotypic changes accompanying acquisition of the PAI and expression of some of its determinants. The esp gene is expressed on the surface of donor and both transconjugants. Biofilm formation and cytolytic activity were enhanced in E. faecalis transconjugants after acquisition of the PAI. No differences in pathogenicity of E. faecalis were detected using a mouse bacteraemia and a mouse peritonitis models (tail vein and intraperitoneal injection). A 66 kb conjugative pheromone-responsive plasmid encoding erm(B) (pLG2) that was transferred in parallel with the PAI was sequenced. pLG2 is a pheromone responsive plasmid that probably promotes the PAI horizontal transfer, encodes antibiotic resistance features and contains complete replication and conjugation modules of enterococcal origin in a mosaic-like composition. The E. faecalis PAI can undergo precise intra- and interspecies transfer probably with the help of conjugative elements like conjugative resistance plasmids, supporting the role of horizontal gene transfer and antibiotic selective pressure in the successful establishment of certain enterococci as nosocomial pathogens.
肠球菌是医院相关性感染的第三大主要原因，由于其通过获得抗生素耐药性和致病性特征快速适应临床环境，因此变得越来越重要。粪肠球菌含有一个 153kb 的致病性岛（PAI），其中包含几个毒力因子，包括肠球菌表面蛋白（esp）。到目前为止，只有 PAI 的内部片段或包含它的更大染色体区域已被转移。在这里，我们证明了来自 UW3114 菌株染色体的整个 PAI 元件的精确切除、环化和水平转移。与参考菌株 MMH594 的 PAI 相比，这个 PAI（约 200kb）包含一些缺失和插入，精确地转移并特异性地整合到粪肠球菌（基因间区）和屎肠球菌（tRNAlys）的染色体中。转移后保留了内部 PAI 结构。我们评估了伴随 PAI 获得的表型变化和一些其决定因素的表达。esp 基因在供体和两个转导子的表面表达。获得 PAI 后，粪肠球菌转导子的生物膜形成和细胞溶解活性增强。在使用小鼠菌血症和腹膜炎模型（尾静脉和腹腔内注射）时，未检测到粪肠球菌致病性的差异。与 PAI 一起转移的编码 erm(B) 的 66kb 可接合型前导肽响应质粒（pLG2）被测序。pLG2 是一种前导肽响应质粒，可能促进 PAI 水平转移，编码抗生素耐药特征，并包含肠球菌起源的完整复制和接合模块，呈镶嵌状组成。粪肠球菌 PAI 可能在诸如接合抗性质粒等接合元件的帮助下进行精确的种内和种间转移，支持水平基因转移和抗生素选择性压力在某些肠球菌成功成为医院病原体中的作用。
