Tripartite Loops Reverse Antibiotic Resistance.

Area of Science:

• Microbiology
• Evolutionary Biology
• Pharmacology

Background:

• Antibiotic resistance is a major threat to modern medicine, driven by bacterial evolution outpacing new drug development.
• Existing strategies to combat resistance are insufficient, necessitating novel approaches to preserve antibiotic efficacy.

Purpose of the Study:

• To introduce and evaluate cyclic antibiotic regimens, termed "tripartite loops," as a strategy to combat antibiotic resistance.
• To investigate the evolutionary dynamics and resensitization potential of bacteria exposed to tripartite loops.

Main Methods:

• Conducted 424 adaptive laboratory evolution experiments using tripartite loops (three-drug cyclic regimens).
• Performed fitness and genomic analyses to understand bacterial adaptation and resistance reversal.
• Tested the strategy on four drug-resistant clinical isolates over 216 evolutionary experiments.

Main Results:

• Bacteria sequentially evolved resistance within tripartite loops but traded resistance for fitness, reverting to sensitivity.
• Tripartite loops promoted evolutionary paths that mitigated fitness costs and reversed resistance.
• Achieved significant resensitization, even with plasmid-mediated resistance, surpassing pairwise regimens.
• Successfully resensitized or eradicated four drug-resistant clinical isolates.

Conclusions:

• Tripartite loops represent a novel sequential antibiotic regimen with high resensitization frequencies.
• This strategy can potentially improve the clinical longevity of existing antibiotics against resistant bacteria.
• The findings offer a promising approach to manage and overcome antibiotic resistance in clinical settings.