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Abstract
Introduction
Although carbapenem-resistant Enterobacteriaceae (CRE) have been thoroughly investigated as the pathogens most commonly associated with clinical infections, data on Serratia marcescens are inadequate and superficial.
Methods
In this study, we characterized 36 carbapenem-resistant Serratia marcescens (CRSM) isolates in our hospital from April 2018 to March 2019 by analysing whole-genome sequencing (WGS) data. The molecular typing of the isolates was performed using both pulsed-field gel electrophoresis (PFGE) and core genome multilocus sequence typing (cgMLST).
Results
Thirty-three of the 36 isolates showed carbapenem resistance conferred by a blaKPC-2-harbouring plasmid, while the remaining three isolates were characterized by overexpression of beta-lactamase combined with porin loss. The blaKPC-2 genes in all the isolates were located on a plasmid of ~103 kb, except one, which was on a plasmid of ~94 kb. The gene structure surrounding blaKPC-2 in the plasmids was confirmed by integration of a partial Tn4401 structure and an intact IS26 as previously reported. Most of the plasmids also contained a mobile genetic element (MGE) comprising qnr and ISKpn19, which provided evidence of horizontal transfer of antibiotic resistance genes.
Conclusion
The thirty-six CRSM isolates were mainly clonally disseminated with a blaKPC-2-harbouring plasmid in our hospital. The gene structure surrounding blaKPC-2 as an MGE, as well as the qnr segment, might be acquired by horizontal gene transfer, and it could aggravate the infection and increase the difficulty of clinical treatment.
Ethics Approval
The collection of CRSM was part of the routine hospital laboratory procedure.
Disclosure
The authors report no conflicts of interest associated with this work.