Strain-level molecular and infection traits are associated with differences in phage efficacy against Pseudomonas aeruginosa.

We identified and characterized a novel lytic phage, HMGUpa1, which exhibited distinct infection efficiency across five characterized P. aeruginosa clinical isolates. While all strains were susceptible to the phage, killing efficacy varied significantly, with strain 50071 showing the highest sensitivity. To explore the basis of this variability, we analyzed phage infection dynamics, host genomic features, and transcriptomic responses. Strain-specific differences in gene content and transcriptional profiles, particularly those related to virulence-associated secretion systems, RNA repair, and metabolic reprogramming, were associated with differences in phage efficacy. These findings suggest that differences in phage efficacy arise from a complex interplay of strain-specific molecular, physiological, and infection-related host traits. Together, our results highlight the importance of considering host-specific traits when developing precision-based phage therapy strategies against multidrug-resistant P. aeruginosa.