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

<b>Background/Objectives:</b> Phages show efficacy against multidrug-resistant <i>Pseudomonas aeruginosa</i>, but limited host ranges require combining them in cocktails. In this work, we characterized 25 <i>P. aeruginosa</i> phages, developed therapeutic cocktails active against diverse clinical isolates, and tested phage efficacy in a mouse incisional wound model. <b>Methods/Results:</b> 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 <i>P. aeruginosa</i> 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). <b>Conclusions:</b> WRAIR_PAM2 covered 76% of highly diverse clinical isolates and demonstrated significant efficacy against topical and systemic <i>P. aeruginosa</i> infection, indicating that it is a promising therapeutic candidate.