Leveraging Temperate Phages To Enhance Antibiotic Effectiveness

Abstract

With a decline in antibiotic effectiveness, there is a renewed interest in using bacterial-specific viruses (bacteriophages or phages) to reduce bacterial loads, alone or with antibiotics. Most phages are therapeutically unsuitable because they are “temperate” and can integrate into the host genome, protecting the host from subsequent phage infections. However, dormant phages can be awakened by stressors such as antibiotics. Here we investigated whether antibiotics can uniquely interact with temperate phages to bias the phage away from dormancy. Model E. coli temperate phage and ciprofloxacin, a DNA-damaging antibiotic, exhibit a potent synergy, resulting in bacterial eradication at sublethal antibiotic concentrations, despite poor killing by the phage alone. Mechanistically, this synergy depletes survivors by awakening dormant phages. To broaden our findings, screening in the multi-drug-resistant pathogen P. aeruginosa, we identified phages that can synergize with four antibiotic classes, despite their widely differing targets - however, these are highly phage, antibiotic, and host-specific. Interestingly, ciprofloxacin also synergized with multiple phages, even in a ciprofloxacin-resistant clinical strain, functionally re-sensitizing the bacterium to the antibiotic. While some of these interactions operated through a mechanism independent of the temperate nature of the phages, ciprofloxacin and piperacillin, a cell wall synthesis inhibitor, specifically reduced the frequency of phage dormancy events. Finally, in a Caenorhabditis elegans infection model, temperate phage-ciprofloxacin pairing increased the lifespan of drug-resistant P. aeruginosa infected worms compared to the uninfected control. Similar rescue was also observed for the phage-carrying strain treated with the antibiotic, supporting that the phage even in its dormant form can enhance antibiotic effectiveness. Overall, we show that temperate phages uniquely synergize with antibiotics at the level of biasing the phage away from dormancy. This is generalizable across phages, antibiotics, and hosts, and shows efficacy in vivo, thereby drastically expanding their therapeutic potential.