A Clinical Extensively-Drug Resistant (XDR) and Role of Its β-Lactamase Genes.

An extensively-drug resistant (XDR) 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 W60. Further cloning analysis was performed to identify determinants of β-lactam/BLI combination resistance. It was found that W60 is resistant to nearly all of the tested antibiotics including all commonly used β-lactam/BLI combinations. Analysis of the genomic structures in W60 showed two novel transferable plasmids are responsible for the resistance phenotypes. Further genetic analysis showed leads to high resistance to β-lactam/BLI combinations, which was enhanced by co-expressing . pECW602 harbors a truncated 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 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 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.