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Updated: May 1, 2026
Quantification of Plasmid-Mediated Antibiotic Resistance in an Experimental Evolution Approach
Published on: December 14, 2019
Exposure to phages has little impact on the evolution of bacterial antibiotic resistance on drug concentration
1State Key Laboratory of Earth Surface Processes and Resource Ecology and MOE Key Laboratory for Biodiversity Science and Ecological Engineering, Beijing Normal University Beijing, China.
Abstract:
The use of phages for treating bacterial pathogens has recently been advocated as an alternative to antibiotic therapy. Here, we test a hypothesis that bacteria treated with phages may show more limited evolution of antibiotic resistance as the fitness costs of resistance to phages may add to those of antibiotic resistance, further reducing the growth performance of antibiotic-resistant bacteria. We did this by studying the evolution of phage-exposed and phage-free Pseudomonas fluorescens cultures on concentration gradients of single drugs, including cefotaxime, chloramphenicol, and kanamycin. During drug treatment, the level of bacterial antibiotic resistance increased through time and was not affected by the phage treatment. Exposure to phages did not cause slower growth in antibiotic-resistant bacteria, although it did so in antibiotic-susceptible bacteria. We observed significant reversion of antibiotic resistance after drug use being terminated, and the rate of reversion was not affected by the phage treatment. The results suggest that the fitness costs caused by resistance to phages are unlikely to be an important constraint on the evolution of bacterial antibiotic resistance in heterogeneous drug environments. Further studies are needed for the interaction of fitness costs of antibiotic resistance with other factors.
Insights
Bacteriophage therapy does not limit antibiotic resistance evolution in Pseudomonas fluorescens. Phage resistance did not impose additional fitness costs on antibiotic-resistant bacteria, suggesting limited impact in diverse drug environments.
Area of Science:
- Microbiology
- Evolutionary Biology
- Bacteriology
Background:
- Antibiotic resistance is a growing global health threat.
- Bacteriophages (phages) are viruses that infect bacteria and are explored as an alternative to antibiotics.
- A hypothesis suggests phages may limit antibiotic resistance evolution due to combined fitness costs.
Purpose of the Study:
- To investigate if phage treatment limits the evolution of antibiotic resistance in bacteria.
- To determine if phage resistance imposes fitness costs that exacerbate antibiotic resistance costs.
Main Methods:
- Studied the evolution of phage-exposed and phage-free Pseudomonas fluorescens cultures.
- Utilized concentration gradients of single antibiotics: cefotaxime, chloramphenicol, and kanamycin.
- Monitored antibiotic resistance levels, bacterial growth, and resistance reversion post-treatment.
Main Results:
- Bacterial antibiotic resistance increased over time, unaffected by phage treatment.
- Phage exposure did not slow the growth of antibiotic-resistant bacteria, but did affect susceptible ones.
- Antibiotic resistance reversion rates were similar in both phage-exposed and phage-free groups.
Conclusions:
- Fitness costs associated with phage resistance are unlikely to significantly constrain bacterial antibiotic resistance evolution in varied drug conditions.
- Further research is required to understand the interplay between antibiotic resistance fitness costs and other environmental factors.
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