Accelerated evolution of resistance in multidrug environments.

Area of Science:

• Microbiology
• Evolutionary Biology
• Pharmacology

Background:

• Multidrug chemotherapy is crucial for treating diseases like malaria, TB, HIV, and cancer.
• The evolution of drug resistance during treatment remains a significant clinical challenge.
• The impact of drug interactions (synergy vs. antagonism) on resistance evolution is poorly understood.

Purpose of the Study:

• To investigate how synergistic and antagonistic drug interactions affect the rate of microbial adaptation and resistance evolution.
• To quantify the influence of drug combination properties on evolutionary trajectories.
• To explore potential mechanisms driving accelerated resistance in synergistic treatments.

Main Methods:

• Development of an automated assay to monitor parallel evolution of hundreds of Escherichia coli populations.
• Exposure of bacterial populations to a two-dimensional grid of drug gradients over multiple generations.
• Direct measurement of adaptation rates under various drug combination conditions.

Main Results:

• A correlation was observed between drug synergy and increased rates of adaptation.
• Evolutionary rates were faster in synergistic drug combinations compared to antagonistic ones.
• Resistance to some synergistic combinations evolved more rapidly than resistance to individual drugs.

Conclusions:

• Synergistic drug combinations, often preferred clinically, can paradoxically accelerate the evolution of drug resistance.
• Accelerated evolution may result from a larger selective advantage for resistance mutations in synergistic treatments.
• Understanding drug-pair properties is crucial for developing novel strategies to combat antibiotic resistance.