AUTHOR=Zhang Feilong , Li Ziyao , Liu Xinmeng , Hu Yanning , Zhao Jiankang , Zhang Yulin , Fan Yanyan , Lei Zichen , Yang Xinrui , Li Zhihua , Li Chen , Wu Yongli , Lu Binghuai 

TITLE=Carbapenem-resistant Citrobacter freundii harboring blaKPC−2 and blaNDM−1: a study on their transferability and potential dissemination via generating a transferrable hybrid plasmid mediated by IS6100

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1239538

DOI=10.3389/fmicb.2023.1239538

ISSN=1664-302X

ABSTRACT=<sec><title>Introduction</title><p>The increase in clinical <italic>Enterobacteriaceae</italic> with dual carbapenemase has become a serious healthcare concern. It is essential to characterize the transferability and potential dissemination of <italic>bla</italic><sub>KPC−2</sub>- and <italic>bla</italic><sub>NDM−1</sub>-coharboring carbapenem-resistant <italic>Citrobacter freundii</italic> (CRCF).</p></sec><sec><title>Methods</title><p>Four <italic>bla</italic><sub>KPC−2</sub>- and <italic>bla</italic><sub>NDM−1</sub>-coharboring CRCF strains were collected from our surveillance of the prevalence of carbapenem-resistant <italic>Enterobacteriaceae</italic>. The isolates were assessed using species identification, antimicrobial susceptibility testing, conjugation assays, whole-genome sequencing, plasmid stability, and fitness costs. Clonality, genome, plasmidome, and phylogeny were analyzed to reveal potential dissemination.</p></sec><sec><title>Results</title><p>Three ST523 <italic>bla</italic><sub>KPC−2</sub>- and <italic>bla</italic><sub>NDM−1</sub>-coharboring CRCF strains, collected from the same hospital within 1 month, exhibited high homology (both identity and coverage &gt;99%), implying clonal dissemination and a small-scale outbreak. Moreover, the <italic>bla</italic><sub>KPC−2</sub> and <italic>bla</italic><sub>NDM−1</sub> genes were coharbored on an IncR plasmid, probably generated by a <italic>bla</italic><sub>KPC−2</sub>-harboring plasmid acquiring <italic>bla</italic><sub>NDM−1</sub>, in these three strains. Importantly, the IncR plasmid may form a transferable hybrid plasmid, mediated by IS<italic>6100</italic> via transposition, with another IncFII plasmid included in the same <italic>C. freundii</italic> strain. Furthermore, the <italic>bla</italic><sub>KPC−2</sub> and <italic>bla</italic><sub>NDM−1</sub> of the fourth CRCF strain are located on two different non-transferable plasmids lacking complete transfer elements. Additionally, throughout the course of the 10-day continuous passage, the genetic surroundings of <italic>bla</italic><sub>NDM−1</sub> in four CRCF strains were gradually excised from their plasmids after the 8th day, whereas they maintained 100% retention for <italic>bla</italic><sub>KPC−2</sub>. Genome and plasmidome analyses revealed that <italic>bla</italic><sub>KPC−2</sub>- or <italic>bla</italic><sub>NDM−1</sub>-harboring <italic>C. freundii</italic> were divergent, and these plasmids have high homology to plasmids of other <italic>Enterobacteriaceae</italic>.</p></sec><sec><title>Conclusion</title><p>Clonal dissemination of ST523 <italic>bla</italic><sub>KPC−2</sub>- and <italic>bla</italic><sub>NDM−1</sub>-coharboring CRCF strains was detected, and we first reported <italic>bla</italic><sub>KPC−2</sub> and <italic>bla</italic><sub>NDM−1</sub> concomitantly located on one plasmid, which could be transferred with mediation by IS<italic>6100</italic> via transposition. Continued surveillance should urgently be implemented.</p></sec>