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Abstract：
An extensively-drug resistant (XDR) Escherichia coli W60 was isolated from the urine sample of a patient. The genetic basis for its XDR phenotype was investigated, particularly the basis for its resistance toward β-lactam/BLI (β-Lactamase Inhibitor) combinations. Following determination of the XDR phenotype, third generation genomic sequencing was performed to identify genetic structures in E. coli W60. Further cloning analysis was performed to identify determinants of β-lactam/BLI combination resistance. It was found that E. coli W60 is resistant to nearly all of the tested antibiotics including all commonly used β-lactam/BLI combinations. Analysis of the genomic structures in E. coli W60 showed two novel transferable plasmids are responsible for the resistance phenotypes. Further genetic analysis showed bla NDM-5 leads to high resistance to β-lactam/BLI combinations, which was enhanced by co-expressing ble MBL. pECW602 harbors a truncated bla TEM that is not functional due to the loss of the N-terminal signal peptide coding region. Research performed in this work leads to several significant conclusions: the XDR phenotype of E. coli W60 can be attributed to the presence of transferable multidrug resistance plasmids; NDM-5 confers high resistance to β-lactam/BLI combinations; co-expression of ble MBL enhances resistance caused by NDM-5; the signal peptides of TEM type β-lactamases are essential for their secretion and function. Findings of this work show the danger of transferable multidrug resistance plasmids and metallo-β-lactamases, both of which should be given more attention in the analysis and treatment of multidrug resistant pathogens.
摘要：
从患者的尿液样品中分离出广泛耐药（XDR）的大肠杆菌W60。研究了其XDR表型的遗传基础,特别是其对β-内酰胺/BLI(β-内酰胺酶抑制剂)组合的抗性的基础。在确定XDR表型后，进行第三代基因组测序以鉴定大肠杆菌W60的遗传结构.进行进一步的克隆分析以鉴定β-内酰胺/BLI组合抗性的决定子。发现大肠杆菌W60对几乎所有测试的抗生素(包括所有常用的β-内酰胺/BLI组合)具有抗性。对大肠杆菌W60中的基因组结构的分析显示两个新的可转移质粒负责抗性表型。进一步的遗传分析显示blaNDM-5导致对β-内酰胺/BLI组合的高抗性,通过共表达bleMBL增强。pECW602具有截短的blaTEM,其由于N末端信号肽编码区的丢失而没有功能。在这项工作中进行的研究得出了几个重要结论：大肠杆菌W60的XDR表型可归因于可转移的多药耐药性质粒的存在；NDM-5赋予对β-内酰胺/BLI组合的高抗性；bleMBL的共表达增强了NDM-5引起的抗性；TEM型β-内酰胺酶的信号肽对于其分泌和功能至关重要。这项工作的结果表明，可转移的多药耐药质粒和金属β-内酰胺酶的危险，在多重耐药病原体的分析和治疗中，应给予更多的关注。
