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Updated: Jan 23, 2026
Quantification of Plasmid-Mediated Antibiotic Resistance in an Experimental Evolution Approach
Published on: December 14, 2019
An MLST approach to support tracking of plasmids carrying OXA-48-like carbapenemase
Carina Brehony1, Elaine McGrath2, Wendy Brennan2
1Antimicrobial Resistance and Microbial Ecology Group, School of Medicine, National University of Ireland, Galway, Ireland.
Objectives:
The prevalence of infections caused by OXA-48-like carbapenemase-producing organisms in Ireland has increased dramatically since 2011 and is an urgent public health issue. Genome-based high-resolution genotyping was used to analyse clinical isolates submitted to the Irish Carbapenemase-Producing Enterobacteriaceae Reference Laboratory Service for a 13 month period (2016-17).
Methods:
A total of 109 OXA-48-producing non-duplicate clinical isolates from 16 submitting centres were sequenced. Using a gene-by-gene approach, isolate genomes were characterized by MLST and core genome MLST, and the presence of antimicrobial resistance determinants was determined. Reference mapping and a novel plasmid MLST-type approach was applied to determine plasmid background.
Results:
The OXA-48-like-producing isolates were Escherichia coli (n = 56), Klebsiella spp. (n = 46) and Enterobacter cloacae (n = 7). Amongst the E. coli isolates there were 37 different STs and amongst the Klebsiella spp. isolates there were 27 different STs. blaOXA-48 was present in 105/109 (96.3%) of isolates. Based on mapping analysis and detection of the pOXA-48 IncL-type plasmid replicon and backbone genes, a pOXA-48-like plasmid was identified in 93/109 isolates (85.3%). The remaining isolates (n = 16; 14.7%) harboured blaOXA-48-like genes in unknown environments. Using a gene-by-gene approach two pOXA-48-like plasmid groups with 2/71 pOXA-48-like locus differences between them were identified.
Conclusions:
In Ireland we found a diversity of genotypes associated with OXA-48-like-producing clinical isolates with the IncL pOXA-48 plasmid type predominating as the blaOXA-48 genetic environment. A plasmid MLST approach can rapidly identify plasmids associated with outbreaks and monitor spread of types temporally and geographically.
Insights
OXA-48-like carbapenemase-producing organisms are a growing threat in Ireland. Genotyping revealed diverse bacterial strains and a predominant IncL plasmid type, highlighting the need for advanced surveillance methods.
Area of Science:
- Microbiology
- Genomics
- Public Health
Background:
- The prevalence of OXA-48-like carbapenemase-producing organisms (CPOs) has significantly increased in Ireland since 2011.
- This rise poses an urgent public health challenge due to the limited treatment options for infections caused by these multidrug-resistant bacteria.
Purpose of the Study:
- To characterize the genetic diversity of OXA-48-like CPOs in Ireland.
- To identify the predominant genetic environments, particularly plasmid types, associated with these resistant organisms.
Main Methods:
- Genome-based high-resolution genotyping, including Multi-Locus Sequence Typing (MLST) and core genome MLST, was performed on 109 clinical isolates.
- Antimicrobial resistance determinants and plasmid backgrounds were analyzed using reference mapping and a novel plasmid MLST approach.
Main Results:
- The study identified 109 OXA-48-producing isolates, primarily Escherichia coli (n=56), Klebsiella spp. (n=46), and Enterobacter cloacae (n=7).
- A high degree of genotypic diversity was observed, with 37 Sequence Types (STs) in E. coli and 27 STs in Klebsiella spp.
- The blaOXA-48 gene was present in 96.3% of isolates, frequently associated with an IncL plasmid type (pOXA-48-like plasmid) identified in 85.3% of cases.
Conclusions:
- A diverse range of genotypes are associated with OXA-48-like CPOs in Ireland.
- The IncL pOXA-48 plasmid type represents the predominant genetic environment for blaOXA-48.
- Plasmid MLST is a valuable tool for rapid identification of outbreak-related plasmids and monitoring their temporal and geographical spread.
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