Characterization of a New Transposon, Tn6696, on ablaNDM-1-Carrying Plasmid From Multidrug-ResistantEnterobacter cloacaessp.dissolvensin China

Background Enterobacter cloacaeis an opportunistic pathogen which is responsible for serious nosocomial infections. A gene which plays an important role in resistance to carbapenems is the New Delhi metallo-beta-lactamase 1 (NDM-1). Currently, the spread of NDM-1-producingE. cloacaestrains is a serious public threat. Methods A multidrug-resistantE. cloacaessp.dissolvensstrain CBG15936 was recovered in 2017 in Guangzhou, China. PCR, S1-pulsed-field gel electrophoresis, and Southern blotting were performed to locate thebla(NDM)(-)(1)gene. Susceptibility testing and conjugation experiments were also performed. Illumina HiSeq and Nanopore sequencers were used to perform whole-genome sequencing. Results Strain CBG15936 belongs to ST932 and is resistant to carbapenems. Thebla(NDM-)(1)gene was found on a similar to 62-kb plasmid, which has a conjugation frequency of 1.68 x 10(-3)events per donor cell. Genome sequencing and analysis revealed that the NDM-1-carrying IncN1 plasmid contained a new transposon Tn6696, which consists of an intactqnrS1-carrying Tn6292element, an inverted 8.3-kb Tn3000remnant, ISkpn19, Delta tnpA, and IS26. Conclusion A new transposon, Tn6696, has been detected on abla(NDM-)(1)-carrying plasmid recovered from multidrug-resistantE. cloacaessp.dissolvensCBG15936 from China. This finding provides a new perspective regarding the potential forbla(NDM-)(1)to undergo horizontal transfer among drug-resistant bacteria.