Modulating the evolutionary trajectory of tolerance using antibiotics with different metabolic dependencies

Area of Science:

• Microbiology and Infectious Diseases
• Evolutionary Biology
• Drug Discovery and Development

Background:

• Antibiotic tolerance, distinct from resistance, enables bacterial survival during treatment, contributing to persistent and recurring infections.
• Tolerant bacteria often exhibit reduced metabolic activity, rendering them less susceptible to conventional antibiotics that target active cellular processes.

Purpose of the Study:

• To investigate the evolutionary pathways of antibiotic tolerance in bacteria.
• To identify mechanisms driving tolerance evolution and explore strategies to counteract it.
• To understand the role of bacterial metabolism in antibiotic efficacy and tolerance development.

Main Methods:

• Experimental evolution of Escherichia coli (E. coli) populations under antibiotic pressure.
• Genomic analysis to identify genetic changes associated with tolerance.
• Metabolic profiling and stress response assays.
• In vitro testing of antibiotic cycling strategies.

Main Results:

• Antibiotic tolerance readily evolved against antibiotics reliant on bacterial metabolism, but not against those with minimal metabolic dependence.
• A key mechanism identified in E. coli involves the deletion of the nhaA gene, leading to decreased metabolism and enhanced stress responses.
• Cycling antibiotics with varying metabolic dependencies effectively inhibited tolerance evolution in vitro, prolonging treatment effectiveness.

Conclusions:

• Bacterial metabolism is a critical factor in the evolution of antibiotic tolerance.
• Targeting metabolism-dependent antibiotics or employing strategic cycling can limit tolerance development.
• This research provides insights for developing novel therapeutic strategies against chronic and recurrent bacterial infections.