Lung infections caused by Gram-positive Staphylococcus aureus and co-infections caused by S. aureus and Gram-negative Pseudomonas aeruginosa are challenging to treat, especially with the rise in the number of antibiotic-resistant strains of these pathogens. Bacteriophage (phage) are bacteria-specific viruses that can infect and lyse bacteria, providing a potentially effective therapy for bacterial infections. However, the development of bacteriophage therapy is impeded by limited suitable biomaterials that can facilitate effective delivery of phage to the lung. Here, we demonstrate the ability of porous microparticles engineered from poly(lactic-co-glycolic acid) (PLGA), a biodegradable polyester, to effectively deliver phage to the lung. The phage-loaded microparticles (phage-MPs) display potent antimicrobial efficacy against various strains of S. aureus in vitro and in vivo, and arrest the growth of a clinical isolate of S. aureus in the presence of sputum supernatant obtained from cystic fibrosis patients. Moreover, phage-MPs efficiently mitigate in vitro co-cultures of S. aureus and P. aeruginosa and display excellent cytocompatibility with human lung epithelial cells. Therefore, phage-MPs represents a promising therapy to treat bacterial lung infection.

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