Genetic Characterization of Enterobacter hormaechei Co-Harboring bla_NDM-1 and mcr-9 Causing Upper Respiratory Tract Infection

Abstract

Purpose

With the spread of multiple drug-resistant bacteria, bla_NDM-1 and mcr-9 have been detected in various bacteria worldwide. However, the simultaneous detection of bla_NDM-1 and mcr-9 in Enterobacter hormaechei has been rarely reported. This study identified an E. hormaechei strain carrying both bla_NDM-1 and mcr-9. We investigated the genetic characteristics of these two resistance genes in detail, elucidating various potential mechanisms by which they may be transmitted.

Methods

Bacterial genomic features and possible origins were assessed by whole-genome sequencing (WGS) with Illumina and PacBio platforms and phylogenetic analysis. Subsequent investigations were performed, including antimicrobial susceptibility testing and multilocus sequence typing (MLST).

Results

We isolated an E. hormaechei strain DY1901 carrying both bla_NDM-1 and mcr-9 from the sputum sample. Susceptibility testing showed that the isolate was multidrug-resistant. Multiple antibiotic resistance genes and virulence genes are widely distributed in DY1901. S1-PFGE, Southern blotting, and plasmid replicon typing showed that DY1901 carried four plasmids. The plasmid carrying mcr-9 was 259Kb in size and belonged to IncHI2, while the plasmid carrying bla_NDM-1 was 45Kb in length and belonged to IncX3.

Conclusion

The E. hormaechei strain isolated in this study has a broad antibiotic resistance spectrum, posing a challenge to clinical treatment. Plasmids carrying mcr-9 are fusion plasmids, and those taking NDM are widely disseminated in China, suggesting that we should conduct routine genomic surveillance on such plasmids to curb the spread of drug-resistant bacteria in the region.

Keywords:

• E. hormaechei
• New Delhi metallo-β-lactamase
• mcr-9
• whole-genome sequencing
• phylogenetic analysis

Data Sharing Statement

The whole-genome sequences of the E. hormaechei were submitted to GenBank under the following BioProject numbers: PRJNA808678.

Ethical Statement

Written informed consents were obtained from patients. This study was conducted following the Declaration of Helsinki and obtained approval from the Medical Ethics Committee at The First Affiliated Hospital of Zhengzhou University. The ethics permit number is KY-2022-0379.

Disclosure

The authors report no conflicts of interest in this work.

Additional information

Funding

This project was supported by the Henan Provincial Key Scientific and Technological Research Program (SBGJ202002114).