Phage Steering in the Presence of a Competing Bacterial Pathogen

The rise of antibiotic-resistant bacteria has necessitated the development of alternative therapeutic strategies such as bacteriophage therapy, where viruses specifically infect bacteria. However, rapid bacterial resistance to phage treatment remains a critical challenge, often leading to failure. Phage steering, which leverages the co-evolutionary dynamics between phage and bacteria, offers a novel solution by driving bacteria to evolve away from virulence factors or resistance mechanisms. In this study, we examined whether phage steering using bacteriophage Luz19 could function in the presence of a competing pathogen, Staphylococcus aureus (USA300), while targeting Pseudomonas aeruginosa (PAO1). Through in vitro co-evolution experiments with and without the competitor, we observed that Luz19 consistently steered P. aeruginosa away from the Type IV Pilus (T4P), a key virulence factor, without interference from S. aureus . Genomic analyses revealed mutations in T4P-associated genes, including pilR and pilZ , which conferred phage resistance. Our findings suggest that Phage Steering remains effective even in polymicrobial environments, providing a promising avenue for enhancing bacteriophage therapy efficacy in complex infections.