AUTHOR=Chen Qichao , Lin Yanfeng , Li Zhonghong , Lu Lanfen , Li Peihan , Wang Kaiying , Yang Lang , Ma Hui , Li Peng , Song Hongbin 

TITLE=Characterization of a New Transposon, Tn6696, on a blaNDM–1-Carrying Plasmid From Multidrug-Resistant Enterobacter cloacae ssp. dissolvens in China

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.525479

DOI=10.3389/fmicb.2020.525479

ISSN=1664-302X

ABSTRACT=<sec><title>Background</title><p><italic>Enterobacter cloacae</italic> is 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-β-lactamase 1 (NDM-1). Currently, the spread of NDM-1-producing <italic>E. cloacae</italic> strains is a serious public threat.</p></sec><sec><title>Methods</title><p>A multidrug-resistant <italic>E. cloacae</italic> ssp. <italic>dissolvens</italic> strain CBG15936 was recovered in 2017 in Guangzhou, China. PCR, S1-pulsed-field gel electrophoresis, and Southern blotting were performed to locate the <italic>bla</italic><sub>NDM</sub><sub>–</sub><sub>1</sub> gene. Susceptibility testing and conjugation experiments were also performed. Illumina HiSeq and Nanopore sequencers were used to perform whole-genome sequencing.</p></sec><sec><title>Results</title><p>Strain CBG15936 belongs to ST932 and is resistant to carbapenems. The <italic>bla</italic><sub>NDM–</sub><sub>1</sub> gene was found on a ∼62-kb plasmid, which has a conjugation frequency of 1.68 × 10<sup>–3</sup> events per donor cell. Genome sequencing and analysis revealed that the NDM-1-carrying IncN1 plasmid contained a new transposon Tn<italic>6696</italic>, which consists of an intact <italic>qnrS1</italic>-carrying Tn<italic>6292</italic> element, an inverted 8.3-kb Tn<italic>3000</italic> remnant, IS<italic>kpn19</italic>, Δ<italic>tnpA</italic>, and IS<italic>26</italic>.</p></sec><sec><title>Conclusion</title><p>A new transposon, Tn<italic>6696</italic>, has been detected on a <italic>bla</italic><sub>NDM–</sub><sub>1</sub>-carrying plasmid recovered from multidrug-resistant <italic>E. cloacae</italic> ssp. <italic>dissolvens</italic> CBG15936 from China. This finding provides a new perspective regarding the potential for <italic>bla</italic><sub>NDM–</sub><sub>1</sub> to undergo horizontal transfer among drug-resistant bacteria.</p></sec>