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Updated: Jan 2, 2026
Detection of Horizontal Gene Transfer Mediated by Natural Conjugative Plasmids in E. coli
Published on: March 24, 2023
The CTX-M conundrum: dissemination of plasmids and Escherichia coli clones
Umaer Naseer1, Arnfinn Sundsfjord
1Research Group for Host-Microbe Interactions, Department of Medical Biology, University of Tromsø, Tromsø, Norway. umaer.naseer@uit.no
Abstract:
The ongoing global spread and increased prevalence of CTX-M-type extended-spectrum β-lactamases in Enterobacteriaceae is of great concern. The successful distribution of CTX-M enzymes mainly involves Escherichia coli causing systemic as well as urinary tract infections in patients worldwide. CTX-M expression is often associated with coresistance that critically reduces treatments options. The mobilization of bla(CTX-M) genes from their original chromosomal position in various Kluyvera species has been facilitated by mobile genetic elements such as ISEcp1 or ISCR1. Molecular epidemiological studies have revealed a thriving linkage of bla(CTX-M) genes to conjugative plasmids and successful bacterial clones. Multireplicon FII plasmids are shown to carry the most widely distributed bla(CTX-M-15) across continents, paving the way for bla(CTX-M-15) into different genetic lineages of E. coli. Dissemination of virulent clones ST131-O25:H4-B2 and ST405-O102:H6-D is now being described worldwide. Importantly, CTX-M-producing strains are uncovering their ability of long-term gastrointestinal colonization often associated with travel to high-prevalent areas. Thus, we are witnessing a global epidemic of bla(CTX-M)-encoding E. coli strains and plasmids, which require serious attention and efficient infection control measures.
Insights
The global spread of CTX-M-type extended-spectrum beta-lactamases in E. coli is a growing concern, leading to difficult-to-treat infections. Mobile genetic elements facilitate the spread of these resistance genes on plasmids, driving a worldwide epidemic.
Area of Science:
- Microbiology
- Genetics
- Epidemiology
Background:
- CTX-M-type extended-spectrum beta-lactamases (ESBLs) are increasingly prevalent in Enterobacteriaceae globally.
- Escherichia coli strains producing CTX-M enzymes are a major cause of systemic and urinary tract infections worldwide.
- Co-resistance associated with CTX-M expression limits therapeutic options.
Purpose of the Study:
- To investigate the molecular epidemiology and dissemination mechanisms of CTX-M-encoding genes in Enterobacteriaceae.
- To highlight the role of mobile genetic elements and plasmids in the spread of bla(CTX-M) genes.
- To underscore the public health threat posed by CTX-M-producing E. coli.
Main Methods:
- Molecular epidemiological studies were conducted.
- Analysis of mobile genetic elements (e.g., ISEcp1, ISCR1) involved in gene mobilization.
- Investigation of plasmid-mediated dissemination, focusing on multireplicon FII plasmids carrying bla(CTX-M-15).
Main Results:
- bla(CTX-M) genes are mobilized by mobile genetic elements and linked to conjugative plasmids and successful bacterial clones.
- Multireplicon FII plasmids are key vehicles for the widespread bla(CTX-M-15) dissemination across E. coli lineages.
- Virulent E. coli clones ST131 and ST405 are globally disseminated.
- CTX-M-producing strains demonstrate long-term gastrointestinal colonization potential.
Conclusions:
- A global epidemic of bla(CTX-M)-encoding E. coli strains and plasmids is evident.
- Efficient infection control measures are urgently needed to address this public health challenge.
- Understanding dissemination mechanisms is crucial for combating antimicrobial resistance.
