Table_2_Genomic Characterization of Multidrug-Resistant Escherichia coli BH100 Sub-strains.DOC

The rapid emergence of multidrug-resistant (MDR) bacteria is a global health problem. Mobile genetic elements like conjugative plasmids, transposons, and integrons are the major players in spreading resistance genes in uropathogenic Escherichia coli (UPEC) pathotype. The E. coli BH100 strain was isolated from the urinary tract of a Brazilian woman in 1974. This strain presents two plasmids carrying MDR cassettes, pBH100, and pAp, with conjugative and mobilization properties, respectively. However, its transposable elements have not been characterized. In this study, we attempted to unravel the factors involved in the mobilization of virulence and drug-resistance genes by assessing genomic rearrangements in four BH100 sub-strains (BH100 MG2014, BH100 MG2017, BH100L MG2017, and BH100N MG2017). Therefore, the complete genomes of the BH100 sub-strains were achieved through Next Generation Sequencing and submitted to comparative genomic analyses. Our data shows recombination events between the two plasmids in the sub-strain BH100 MG2017 and between pBH100 and the chromosome in BH100L MG2017. In both cases, IS3 and IS21 elements were detected upstream of Tn21 family transposons associated with MDR genes at the recombined region. These results integrated with Genomic island analysis suggest pBH100 might be involved in the spreading of drug resistance through the formation of resistance islands. Regarding pathogenicity, our results reveal that BH100 strain is closely related to UPEC strains and contains many IS3 and IS21-transposase-enriched genomic islands associated with virulence. This study concludes that those IS elements are vital for the evolution and adaptation of BH100 strain.

多重耐药（MDR）细菌的快速涌现已成为全球性公共卫生难题。接合性质粒、转座子与整合子等可移动遗传元件，是尿路致病性大肠杆菌（UPEC）致病型中耐药基因扩散的核心介导因子。大肠杆菌BH100菌株于1974年从一名巴西女性的泌尿道中分离得到，该菌株携带两个搭载多重耐药盒的质粒：pBH100与pAp，二者分别具备接合特性与可迁移特性，但其转座元件尚未得到系统解析。本研究通过分析四株BH100亚菌株（BH100 MG2014、BH100 MG2017、BH100L MG2017及BH100N MG2017）的基因组重排现象，试图阐明毒力与耐药基因迁移过程中的关键影响因素。研究通过下一代测序（Next Generation Sequencing）完成了各BH100亚菌株的全基因组组装，并开展比较基因组分析。结果显示，BH100 MG2017亚菌株中发生了两个质粒间的重组事件，而BH100L MG2017亚菌株中则存在pBH100质粒与染色体之间的重组事件；两类重组区域内，与多重耐药基因相关的Tn21家族转座子上游均检测到IS3与IS21元件。结合基因组岛分析结果，上述数据提示pBH100可能通过形成耐药岛参与耐药基因的传播。在致病性层面，研究结果表明BH100菌株与尿路致病性大肠杆菌菌株亲缘关系紧密，且携带多个富集转座酶、与毒力相关的基因组岛。本研究最终证实，此类插入序列元件对于BH100菌株的进化与适应至关重要。