A Novel SXT/R391 Integrative and Conjugative Element Carries Two Copies of the Gene in Proteus mirabilis.

The rapid spread of the gene is a major public health concern. Here, we describe the multidrug-resistant Proteus mirabilis strain XH1653, which contains a novel SXT/R391 integrative and conjugative element (ICE), harboring two tandem copies of and 21 other resistance genes. XH1653 was resistant to all antibiotics tested, apart from aztreonam. Whole-genome data revealed that two copies of embedded in the IS element are located in HS4 of the novel ICE, which we named ICEChnXH1653. A circular intermediate of ICEChnXH1653 was detected by PCR, and conjugation experiments showed that the ICE can be transferred to the Escherichia coli strain EC600 with frequencies of 1.5 × 10. In the recipient strain, the ICE exhibited a higher excision frequency and extrachromosomal copy number than the ICE in the donor strain. We also observed that the presence of ICEChnXH1653 has a negative impact on bacterial fitness and leads to changes in the transcriptome of the host. evolution experiments under nonselective conditions showed that the two tandem copies of the IS element and the IS element can be lost during repeated laboratory passage. This is the first report of a novel SXT/R391 ICE carrying two tandem copies of , which also illustrates the role that ICEs may play as platforms for the accumulation and transmission of antibiotic resistance genes. The occurrence of carbapenemase-producing Proteus mirabilis, especially those strains producing NDM-1 and its variants, is a major public health concern worldwide. The integrative conjugative element (ICE) plays an important role in horizontal acquisition of resistance genes. In this study, we characterized a novel SXT/R391 ICE from a clinical P. mirabilis isolate that we named ICEChnXH1653, which contains two tandem copies of the carbapenemase gene . We performed an integrative approach to gain insights into different aspects of ICEChnXH1653 evolution and biology and observed that ICEChnXH1653 obtained the carbapenemase gene by IS-mediated homologous recombination. Our study reveals that the transmission of by IS elements or ICEs may be an important contributor to the carbapenem resistance development across species, which could improve our understanding of horizontal gene transfer in clinical environments.