Occurrence of Serratia marcescens Carrying blaIMP-26 and mcr-9 in Southern China: New Insights in the Evolution of Megaplasmid IMP-26

Abstract

The spread of multidrug-resistant enterobacteria strains has posed a significant concern in public health, especially when the strain harbors metallo-beta-lactamase (MBL)-encoding and mobilized colistin resistance (mcr) genes as such genetic components potentially mediate multidrug resistance. Here we report an IncHI2/2A plasmid carrying blaIMP-26 and mcr-9 in multidrug-resistant Serratia marcescens human isolates YL4. Antimicrobial susceptibility testing was performed by the broth microdilution method. According to the results, S. marcescens YL4 was resistant to several antimicrobials, including β-lactams, fluorquinolones, sulfanilamide, glycylcycline, and aminoglycosides, except for amikacin. To investigate the plasmid further, we conducted whole-genome sequencing and sequence analysis. As shown, S. marcescens YL4 possessed a circular chromosome with 5,171,477 bp length and two plasmids, pYL4.1 (321,744 bp) and pYL4.2 (46,771 bp). Importantly, sharing high similarity with plasmids pZHZJ1 and pIMP-26, pYL4.1 has an IncHI2/2A backbone holding a variable region containing blaIMP-26, mcr-9, and two copies of blaTEM-1B. After comprehensively comparing relevant plasmids, we proposed an evolutionary pathway originating from ancestor pZHZJ1. Then, via an acquisition of the mcr-9 element and a few recombination events, this plasmid eventually evolved into pYL4.1 and pIMP-26 through two different pathways. In addition, the phage-like plasmid pYL4.2 also carried a blaTEM-1B gene. Remarkably, this study first identified a multidrug-resistant S. marcescens strain co-harboring blaIMP-26 and mcr-9 on a megaplasmid pYL4.1 and also included a proposed evolutionary pathway of epidemic megaplasmids carrying blaIMP-26.

Detection of clinical Serratia marcescens isolates carrying blaKPC-2 in a hospital in China

“…In this study, the genetic context “ repB -IS Kpn6 - bla KPC-2 -IS kpn27 - pinE “ was present in pSMBC31-39K-like and pSMBC50-107K-like plasmids, implying a high rate of transmission for this region. Additionally, S. marcescens has been found to harbor mcr gene ( mcr-9 ) [ 44 , 45 ], which poses a risk-associated resistance against colistin in Enterobacteriaceae . Although tet (X) tigecycline resistance gene has not yet been detected in this bacterium, vigilance should be maintained regarding its potential coexistence with multiple important AMR genes mentioned above.…”

Genomic characterization of two carbapenem-resistant Serratia marcescens isolates causing bacteremia: Emergence of KPC-2-encoding IncR plasmids

“…Serratia marcescens is a well-known opportunistic pathogen that is often seen to be responsible for infections in intensive care, surgical and dialysis facilities ( Ferreira et al., 2020 ). Antimicrobial resistance of S. marcescens has not been widely explored in China ( Lin et al., 2016 ; Su et al., 2017 ; Huang et al., 2021 ; Zhong et al., 2022 ; Hou et al., 2022 ). Herein, we found two carbapenem-resistant S. marcescens from patients with bloodstream infections in China, and the bla KPC-2 gene, which is native to the area, is likely to be disseminated through the transmission of IncR plasmids.…”

Serratia marcescens antibiotic resistance mechanisms of an opportunistic pathogen: a literature review

“…(2021) recovered a carbapenem-resistant strain from a patient with asymptomatic bacteriuria, the resistant phenotype was associated with production of IMP-4 from a conjugative plasmid. A multi-resistant S. marcescens isolate carrying both genes bla IMP-26 and mcr-9 within the IncHI2/2A megaplasmid was isolated during 2022 in China ( Zhong et al, 2022 ).…”