Related Experiment Video
Updated: Sep 6, 2025
Constructing Mutants in Serotype 1 Streptococcus pneumoniae strain 519/43
Published on: September 11, 2020
Amoxicillin-resistant Streptococcus pneumoniae can be resensitized by targeting the mevalonate pathway as indicated
Liselot Dewachter1, Julien Dénéréaz1, Xue Liu1,2
1Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Biophore Building, Lausanne, Switzerland.
Abstract:
Antibiotic resistance in the important opportunistic human pathogen Streptococcus pneumoniae is on the rise. This is particularly problematic in the case of the β-lactam antibiotic amoxicillin, which is the first-line therapy. It is therefore crucial to uncover targets that would kill or resensitize amoxicillin-resistant pneumococci. To do so, we developed a genome-wide, single-cell based, gene silencing screen using CRISPR interference called sCRilecs-seq (subsets of CRISPR interference libraries extracted by fluorescence activated cell sorting coupled to next generation sequencing). Since amoxicillin affects growth and division, sCRilecs-seq was used to identify targets that are responsible for maintaining proper cell size. Our screen revealed that downregulation of the mevalonate pathway leads to extensive cell elongation. Further investigation into this phenotype indicates that it is caused by a reduced availability of cell wall precursors at the site of cell wall synthesis due to a limitation in the production of undecaprenyl phosphate (Und-P), the lipid carrier that is responsible for transporting these precursors across the cell membrane. The data suggest that, whereas peptidoglycan synthesis continues even with reduced Und-P levels, cell constriction is specifically halted. We successfully exploited this knowledge to create a combination treatment strategy where the FDA-approved drug clomiphene, an inhibitor of Und-P synthesis, is paired up with amoxicillin. Our results show that clomiphene potentiates the antimicrobial activity of amoxicillin and that combination therapy resensitizes amoxicillin-resistant S. pneumoniae. These findings could provide a starting point to develop a solution for the increasing amount of hard-to-treat amoxicillin-resistant pneumococcal infections.
Insights
Researchers identified a new strategy to combat amoxicillin-resistant Streptococcus pneumoniae. Inhibiting undecaprenyl phosphate synthesis with clomiphene resensitizes bacteria to amoxicillin, offering hope against resistant infections.
Area of Science:
- Microbiology
- Molecular Biology
- Drug Discovery
Background:
- Antibiotic resistance in *Streptococcus pneumoniae*, a major human pathogen, is a growing global health concern.
- Amoxicillin, a first-line treatment, is becoming less effective against resistant strains, necessitating novel therapeutic strategies.
- Understanding the mechanisms of amoxicillin resistance is crucial for developing effective treatments.
Purpose of the Study:
- To identify novel targets for resensitizing amoxicillin-resistant *Streptococcus pneumoniae* to amoxicillin.
- To investigate the role of the mevalonate pathway in maintaining pneumococcal cell size and division.
- To develop and validate a combination therapy for treating amoxicillin-resistant pneumococcal infections.
Main Methods:
- Genome-wide CRISPR interference (CRISPRi) screen using a single-cell based approach (sCRilecs-seq) to identify genes essential for cell size maintenance.
- Analysis of cell elongation phenotype resulting from gene silencing.
- Biochemical investigation into cell wall precursor synthesis and transport.
- Combination therapy testing using amoxicillin and clomiphene (an undecaprenyl phosphate synthesis inhibitor).
Main Results:
- Downregulation of the mevalonate pathway led to significant cell elongation in *S. pneumoniae*.
- This cell elongation was attributed to reduced undecaprenyl phosphate (Und-P) availability, hindering cell wall precursor transport and specifically halting cell constriction.
- Combination therapy with amoxicillin and clomiphene demonstrated potentiation of antimicrobial activity and resensitization of amoxicillin-resistant strains.
Conclusions:
- Targeting the mevalonate pathway and undecaprenyl phosphate synthesis offers a promising strategy to overcome amoxicillin resistance in *S. pneumoniae*.
- The combination of amoxicillin and clomiphene effectively resensitizes resistant pneumococci, providing a potential therapeutic approach.
- These findings represent a significant step towards addressing the challenge of hard-to-treat amoxicillin-resistant pneumococcal infections.
