First Report of Coexistence of blaSFO–1 and blaNDM–1 β-Lactamase Genes as Well as Colistin Resistance Gene mcr-9 in a Transferrable Plasmid of a Clinical Isolate of Enterobacter hormaechei

Abstract

Many antimicrobial resistance genes usually located on transferable plasmids are responsible for multiple antimicrobial resistance among multidrug-resistant (MDR) Gram-negative bacteria. The aim of this study is to characterize a carbapenemase-producing Enterobacter hormaechei 1575 isolate from the blood sample in a tertiary hospital in Wuhan, Hubei Province, China. Antimicrobial susceptibility test showed that 1575 was an MDR isolate. The whole genome sequencing (WGS) and comparative genomics were used to deeply analyze the molecular information of the 1575 and to explore the location and structure of antibiotic resistance genes. The three key resistance genes (blaSFO–1, blaNDM–1, and mcr-9) were verified by PCR, and the amplicons were subsequently sequenced. Moreover, the conjugation assay was also performed to determine the transferability of those resistance genes. Plasmid files were determined by the S1 nuclease pulsed-field gel electrophoresis (S1-PFGE). WGS revealed that p1575-1 plasmid was a conjugative plasmid that possessed the rare coexistence of blaSFO–1, blaNDM–1, and mcr-9 genes and complete conjugative systems. And p1575-1 belonged to the plasmid incompatibility group IncHI2 and multilocus sequence typing ST102. Meanwhile, the pMLST type of p1575-1 was IncHI2-ST1. Conjugation assay proved that the MDR p1575-1 plasmid could be transferred to other recipients. S1-PFGE confirmed the location of plasmid with molecular weight of 342,447 bp. All these three resistant genes were flanked by various mobile elements, indicating that the blaSFO–1, blaNDM–1, and mcr-9 could be transferred not only by the p1575-1 plasmid but also by these mobile elements. Taken together, we report for the first time the coexistence of blaSFO–1, blaNDM–1, and mcr-9 on a transferable plasmid in a MDR clinical isolate E. hormaechei, which indicates the possibility of horizontal transfer of antibiotic resistance genes.

Co-occurrence of blaNDM–1 and mcr-9 in a Conjugative IncHI2/HI2A Plasmid From a Bloodstream Infection-Causing Carbapenem-Resistant Klebsiella pneumoniae

“…Although mcr-9 was first identified in 2019, recent research indicates that it has existed for a long time and has been spreading among CRKP isolates of human origin in Europe since 2013 (Wang et al, 2020). In China, clinical isolates of Enterobacteriales co-harboring bla NDM−1 and mcr-9 have been reported, all of which belong to Enterobacter spp., and the bla NDM−1 and mcr-9 genes were harbored by different plasmids in most strains (Yuan et al, 2019;Lin et al, 2020;Ai et al, 2021).…”

“…With 81% query coverage and 99.97% identity in BLASTn, the sequence of pK55602_2 was partially consistent with that of plasmid p1575-1 (accession no. CP068288), a recently reported bla NDM−1 -mcr-9-co-positive-IncHI2 plasmid harbored by a clinical isolate of Enterobacter hormaechei (Ai et al, 2021; Figure 1). Further analyses revealed that the pK710429_2 sequence can be roughly divided into two distinct regions based on its similarity to different plasmids.…”

“…Among them, mcr-9 is a newly emerging variant first identified from a clinical Salmonella enterica isolate in the United States in 2019 (Carroll et al, 2019). Notably, co-transfer of mcr-9 and carbapenemase-encoding genes (e.g., bla NDM , bla IMP , and bla VIM ) by a single plasmid has been detected in clinical isolates of Enterobacter spp., but not yet reported in Klebsiella species (Chavda et al, 2019;Li et al, 2020;Ai et al, 2021).…”

“…The transferability of the bla NDM−1 and mcr-9 genes was assessed using conjugation as previously described (Ai et al, 2021). Approximately 1 × 10 8 colony-forming units (CFU)/mL of the donor strain (KPN710429) and the recipient strain (sodium azide-resistant E. coli J53) were mixed at 1:1 ratio and spotted onto filter membrane, which were placed on Muller-Hinton (MH) agar plates and incubated for 18-24 h at 37 • C. Transconjugants were selected on MH agar containing both sodium azide (300 µg/mL) and ceftriaxone (32 µg/mL).…”

The Co-occurrence of NDM-5, MCR-1, and FosA3-Encoding Plasmids Contributed to the Generation of Extensively Drug-Resistant Klebsiella pneumoniae

“…The S1-pulsed-field gel electrophoresis (S1-PFGE) was performed to further determine the existence of plasmids in the original isolate K. pneumoniae 1678, and its transformants and transconjugants. PFGE plugs of all these strains were prepared and digested as previously described ( Ai et al, 2021 ). Briefly, the isolates were embedded in 10 g/L of Seakem Gold gel, and digested with endonuclease S1 nuclease (Takara, Dalian, China).…”