Novel IncR/IncP6 Hybrid Plasmid pCRE3-KPC Recovered from a Clinical KPC-2-Producing Citrobacter braakii Isolate.

carbapenemase (KPC)-producing have become widespread in hospitals and the environment. Here, we describe a -carrying plasmid called pCRE3-KPC, which was recovered from a clinical multidrug-resistant CRE3 strain in China. The complete nucleotide sequence of pCRE3-KPC was determined by combining MiSeq and MinION sequencing and then compared with those of three related plasmids. Plasmid conjugal transfer and electroporation tests, modified carbapenem inactivation method, and bacterial antimicrobial susceptibility test were carried out. We compared this plasmid with three related plasmids to verify that the backbone of pCRE3-KPC was composed of the backbones of the IncR plasmid and IncP6 plasmid. Further bioinformatics analysis showed that pCRE3-KPC carried two resistance-related regions (the gene cluster and the --related region). The --related region included two novel insertion sequences (IS and IS). Reports of human-pathogenic strains, especially of strains showing resistance to carbapenems, are rare. To the best of our knowledge, our results represent the first detection of carbapenemase gene in strains. In addition, we have studied detailed genetic characteristics of the novel IncR/IncP6 hybrid plasmid pCRE3-KPC, which was isolated from a clinical multidrug-resistant CRE3 strain. Our results may provide further insight into the horizontal transfer of multidrug resistance genes in bacteria and into the genomic diversity and molecular evolution of plasmids.