Rapid Evolution of Ionic Silver Resistance in Escherichia coli phage T7
Antimicrobial resistance crisis has led to the use of metals and bacteriophages assuitable alternatives to chemical antibiotics. Combination methods have been developedutilizing ionic/nano-silver and bacteriophages against multi-drug-resistant bacteria.However, these methods have often failed to examine the impact of silver on the efficacyof bacteriophages. Here we utilize experimental evolution to evolve resistance to ionicsilver in bacteriophage T7. Evolution of resistance was rapid as evidenced by recoveryof phage growth in E. coli after repeated exposures to ionic silver, greater capacity ofsilver-selected compared to the control and ancestral phages to infect E. coli uponexposure to increasing amounts of ionic silver and greater ability to impede E. coligrowth in standard medium. Silver resistance evolved without loss to thermal or pHstability. The genomic foundation of silver resistance was simple, with positive- andnegative natural selection differentiating the silver-selected populations from the controlsand ancestor population across serial passages in silver. The implications of these arediscussed in reference to designing phage/silver combination approaches againstmultidrug resistant bacteria