A case report of bacteriophage therapy for the treatment of lung infection due to carbapenem-resistant Pseudomonas aeruginosa.

In recent years, with the increasing global antimicrobial resistance, bacteriophage therapy has emerged as one of the most promising alternatives to antibiotics. Numerous studies have reported the effectiveness and safety of phage therapy in treating multidrug-resistant bacterial infections. However, there is limited research on the relationship between the emergence of phage-resistant strains and clinical outcomes. In this study, we applied phage nebulization therapy to a patient with carbapenem-resistant Pseudomonas aeruginosa lung infection. After 8 weeks of treatment with P. aeruginosa phages, the patient's sputum bacterial load decreased, overall inflammatory markers decreased, and lung effusion significantly reduced despite isolation of phage-resistant strains. Whole-genome sequencing of resistant isolates, coupled with Galleria mellonella larvae infection modeling, revealed a trade-off effect, demonstrating attenuated virulence associated with phage resistance. This finding underscores the potential for phage therapy to achieve positive clinical outcomes even in the face of resistance development, highlighting the need for a nuanced understanding of phage-bacteria coevolution in clinical settings.