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Updated: May 22, 2025
Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance
Published on: May 2, 2018
Combination therapy delays antimicrobial resistance after adaptive laboratory evolution of Staphylococcus aureus
Maiken Engelbrecht Petersen1, Amanda Batoul Khamas1, Lars Jørgen Østergaard2
1Interdisciplinary Nanoscience Center, Aarhus University, Aarhus, Denmark.
Abstract:
Antibiotic resistance, driven by misuse and overuse of antibiotics, is one of the greatest threats against human health. The antimicrobial pressure during prolonged antibiotic treatment of chronic bacterial infections selects for resistance. While antibiotic combinations may reduce resistance emergence, antibiotic-tolerant persister cells can serve as a reservoir for resistance development. Therefore, targeting these cells with anti-persister drugs might provide a novel strategy for resistance prevention. In this study, we conducted 42 days of adaptive laboratory evolution using Staphylococcus aureus exposed to rifampicin, ciprofloxacin, daptomycin, and vancomycin, alone or in combination with the anti-persister drug mitomycin C. We monitored antibiotic susceptibility daily and assessed phenotypic changes in growth and biofilm formation in evolved strains. Whole-genome sequencing revealed mutations linked to antibiotic resistance and phenotypic shifts. Rifampicin resistance developed within a few days, while ciprofloxacin and daptomycin emerged in approximately 3 weeks. Treatments with vancomycin or mitomycin C resulted in minimal changes in susceptibility. While combination therapy delayed resistance, it did not fully prevent it. Notably, the combination of rifampicin with mitomycin C maintained rifampicin susceptibility throughout the long-term evolution experiment. Sub-inhibitory antibiotic treatments selected for both previously characterized and novel mutations, including unprecedented alterations in the nucleotide excision repair system and azoreductase following mitomycin C exposure. The delayed resistance development observed with combination therapy, particularly mitomycin C's ability to suppress rifampicin resistance, suggests potential therapeutic applications. Future studies should evaluate the clinical efficacy of anti-persister drugs in preventing resistance across different bacterial pathogens and infection models.
Insights
Targeting persister cells with anti-persister drugs like mitomycin C may prevent antibiotic resistance. Combining antibiotics with mitomycin C delayed resistance, and notably suppressed rifampicin resistance in Staphylococcus aureus.
Area of Science:
- Microbiology
- Molecular Biology
- Drug Discovery
Background:
- Antibiotic resistance is a major global health threat, exacerbated by prolonged treatments and the emergence of persister cells.
- Persister cells, tolerant to antibiotics, can harbor resistance mechanisms and contribute to treatment failure in chronic infections.
- Targeting persister cells with novel anti-persister drugs presents a promising strategy to prevent antibiotic resistance development.
Purpose of the Study:
- To investigate the efficacy of combining antibiotics with the anti-persister drug mitomycin C in preventing antibiotic resistance.
- To analyze the genetic and phenotypic changes associated with adaptive laboratory evolution under antibiotic pressure.
- To explore the potential of mitomycin C in suppressing resistance emergence in *Staphylococcus aureus*.
Main Methods:
- Adaptive laboratory evolution of *Staphylococcus aureus* over 42 days using various antibiotics alone or with mitomycin C.
- Daily monitoring of antibiotic susceptibility and assessment of phenotypic changes (growth, biofilm formation).
- Whole-genome sequencing to identify mutations linked to resistance and phenotypic shifts.
Main Results:
- Rifampicin resistance emerged rapidly, while ciprofloxacin and daptomycin resistance took approximately 3 weeks.
- Vancomycin and mitomycin C alone showed minimal impact on susceptibility.
- Combination therapy delayed resistance, with the rifampicin-mitomycin C combination uniquely maintaining rifampicin susceptibility throughout the experiment.
- Mitomycin C exposure led to novel mutations in DNA repair and azoreductase systems.
Conclusions:
- Combination therapy, especially with anti-persister drugs like mitomycin C, can delay antibiotic resistance.
- Mitomycin C demonstrates potential in preventing resistance to specific antibiotics, such as rifampicin.
- Further research is warranted to evaluate the clinical applicability of anti-persister drugs in combating resistance in various infections.
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