Plasmid analysis of NDM metallo-β-lactamase-producing Enterobacteriacea

Introduction

Carbapenemase-producing bacteria pose a significant threat to public health due to their broad resistance to β-lactam antibiotics and further substance classes. NDM-1 is the second most abundant carbapenemase in Enterobacteriacae in Germany [1]. Understanding the genetic environment of β-lactamase genes and their dissemination pathways is crucial for effective treatment and infection control strategies.

Goals

We performed comprehensive genome analyses of NDM-producing clinical Enterobacteriaceae to map the diversity of plasmids and to understand the inter- and intraspecific distribution of antibiotic resistance genes. Multiple isolates were obtained from patients with a recent travel history abroad.

Methods

Genome sequencing (Illumina and Nanopore) was performed for 28 NDM-producing isolates. Detected plasmids were compared with plasmids from the public available database NCBI. Susceptibilities to antibiotics (broth microdilution) and antibiotic resistance transfer (conjugation assays into E. coli J53) were tested.

Results

Hybrid-assemblies enabled the circularization of 24 out of 28 plasmids. The plasmids sizes ranged from 47-396 kbp and different Inc-types (IncC, IncFIA, IncFIB, IncX3, IncR) were found. Nucleotide based comparison of the plasmids show a large diversity, both within the Enterobacteriaceae and within individual species. Various resistance genes and several virulence associated genes were located on these plasmids. In addition to 21 blaNDM-1 six blaNDM-5 and one blaNDM-19 were found. No correlations were found between the place of isolation or the travel background of the patients and the blaNDM genetic environment of the isolates. Conjugative transfer was successful for 13 of these 28 plasmids.

Conclusions

Our analyses showed a high diversity in plasmids carrying blaNDM and their horizontal spread in different Enterobacteriaceae species. Genomic surveillance with the focus on plasmid analysis will improve our understanding on dissemination of carbapenemase genes.

[1] Pfennigwerth et al., (2023). Bericht des Nationalen Referenzzentrums für gramnegative Krankenhauserreger.