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Author Spotlight: Advancing Antibiotic Resistance Research Using an Efflux-Deficient Bacterial Strain and a Single-Copy Gene Expression System
Published on: January 5, 2024
A shared mechanism of multidrug resistance in laboratory-evolved uropathogenic Escherichia coli
Nakjun Choi1, Eunna Choi1, Yong-Joon Cho2
1Department of Life Sciences, School of Life Sciences and Biotechnology, Korea University, Seoul, South Korea.
Abstract:
The emergence of multidrug-resistant bacteria poses a significant threat to human health, necessitating a comprehensive understanding of their underlying mechanisms. Uropathogenic Escherichia coli (UPEC), the primary causative agent of urinary tract infections, is frequently associated with multidrug resistance and recurrent infections. To elucidate the mechanism of resistance of UPEC to beta-lactam antibiotics, we generated ampicillin-resistant UPEC strains through continuous exposure to low and high levels of ampicillin in the laboratory, referred to as Low AmpR and High AmpR, respectively. Whole-genome sequencing revealed that both Low and High AmpR strains contained mutations in the marR, acrR, and envZ genes. The High AmpR strain exhibited a single additional mutation in the nlpD gene. Using protein modeling and qRT-PCR analyses, we validated the contributions of each mutation in the identified genes to antibiotic resistance in the AmpR strains, including a decrease in membrane permeability, increased expression of multidrug efflux pump, and inhibition of cell lysis. Furthermore, the AmpR strain does not decrease the bacterial burden in the mouse bladder even after continuous antibiotic treatment in vivo, implicating the increasing difficulty in treating host infections caused by the AmpR strain. Interestingly, ampicillin-induced mutations also result in multidrug resistance in UPEC, suggesting a common mechanism by which bacteria acquire cross-resistance to other classes of antibiotics.
Insights
Multidrug-resistant Uropathogenic Escherichia coli (UPEC) strains developed ampicillin resistance through mutations in specific genes. These mutations also conferred cross-resistance to other antibiotics, complicating treatment.
Area of Science:
- Microbiology
- Genetics
- Pharmacology
Background:
- Multidrug-resistant bacteria, particularly Uropathogenic Escherichia coli (UPEC), present a major global health challenge.
- UPEC is a leading cause of urinary tract infections and is often linked to multidrug resistance and recurring infections.
Purpose of the Study:
- To investigate the genetic mechanisms underlying ampicillin resistance in UPEC.
- To understand how UPEC acquires resistance to beta-lactam antibiotics.
Main Methods:
- Generation of ampicillin-resistant UPEC strains (Low AmpR and High AmpR) via laboratory exposure.
- Whole-genome sequencing to identify mutations in resistant strains.
- Protein modeling and qRT-PCR to validate the functional impact of identified mutations.
Main Results:
- Mutations in marR, acrR, and envZ genes were found in both Low and High AmpR strains.
- An additional mutation in the nlpD gene was observed in the High AmpR strain.
- These mutations led to decreased membrane permeability, increased multidrug efflux pump expression, and inhibited cell lysis.
- Ampicillin-resistant UPEC strains showed reduced efficacy in clearing bacterial burden in a mouse model.
- Acquired ampicillin resistance correlated with cross-resistance to other antibiotic classes.
Conclusions:
- Specific genetic mutations confer ampicillin resistance in UPEC by altering cellular processes.
- Ampicillin resistance in UPEC is associated with increased multidrug resistance, posing therapeutic challenges.
- The study highlights a common pathway for acquiring cross-resistance in bacteria.
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