Optimal bacteriophage mutation rates for phage therapy

Area of Science:

• Microbiology
• Genetics
• Evolutionary Biology

Background:

• Bacteriophages (phages) are viruses that infect bacteria and are explored for antimicrobial therapy.
• Phage mutation can generate variants that overcome bacterial resistance, but also accumulate deleterious mutations.
• Understanding the role of mutation rate is crucial for optimizing phage therapy effectiveness.

Purpose of the Study:

• To model the impact of varying bacteriophage mutation rates on the efficacy of phage therapy.
• To identify an optimal mutation rate that balances beneficial and deleterious mutations.
• To assess the influence of inoculum density and mutation-selection balance on phage therapy outcomes.

Main Methods:

• Mathematical modeling was used to simulate phage-bacterial interactions under different mutation rates.
• The study analyzed the trade-offs between beneficial mutations (overcoming resistance) and deleterious mutations (genetic load).
• Parameters such as mutation rate, inoculum density, and selective coefficients were varied in the model.

Main Results:

• An approximate mutation rate of 0.1 deleterious mutations per genome per generation represents a balance between beneficial diversity and genetic load.
• Increased phage inoculum density can unexpectedly elevate resistant bacterial populations by limiting in situ mutant phage production.
• Engineering higher mutation rates beyond the optimum is beneficial only with very weak selection against deleterious mutations ( < 0.01).

Conclusions:

• The optimal bacteriophage mutation rate is critical for effective phage therapy, balancing adaptation and genetic load.
• Phage therapy strategies should consider inoculum density to avoid unintended increases in bacterial resistance.
• Modifying mutation rates requires careful consideration of selection pressures to avoid negative impacts on therapeutic efficacy.