Pseudomonas aeruginosa Phage Cocktails: Rational Design and Efficacy Against Mouse Wound and Systemic Infection

Background/Objectives: Phages show efficacy against multidrug-resistant Pseudomonas aeruginosa, but limited host ranges require combining them in cocktails. In this work, we characterized 25 P. aeruginosa phages, developed therapeutic cocktails active against diverse clinical isolates, and tested phage efficacy in a mouse incisional wound model. Methods/Results: These phages represent seven genera, and genomic and phenotypic analyses indicate that 24/25 are lytic and suitable for phage therapy. Phage host ranges on a diversity panel of 156 P. aeruginosa strains that included 106 sequence types varied from 8% to 54%, and together the 24 lytic phages were active against 133 strains (85%). All of the phages reduced bacterial counts in biofilms. A cocktail of five lytic phages, WRAIR_PAM1, covered 56% of the strain panel, protected 100% of mice from lethal systemic infection (vs. 20% survival in the saline-treated group), and accelerated healing of infected wounds. An improved five-phage cocktail, WRAIR_PAM2, was formulated by a rational design approach (using phages with broader host ranges, more complementing activity, relatively low resistance background, and compatibility in mixes). Conclusions: WRAIR_PAM2 covered 76% of highly diverse clinical isolates and demonstrated significant efficacy against topical and systemic P. aeruginosa infection, indicating that it is a promising therapeutic candidate.