Biological characterization of the lytic Pseudomonas aeruginosa phage BUCT980 and its therapeutic efficacy in a murine lung infection model.

Pseudomonas aeruginosa is an important opportunistic pathogen whose increasing multidrug resistance limits conventional antimicrobial treatment options and underscores the need for alternative antibacterial strategies. In this study, we isolated and systematically characterized a novel lytic phage, BUCT980, and evaluated its antibacterial activity and therapeutic potential. Transmission electron microscopy showed that BUCT980 is a myovirus. One-step growth analysis indicated an apparent latent period of approximately 60 min and a burst size of approximately 173 PFU per infected cell. The BUCT980 genome is 60,697 bp in length, and comparative genomic and phylogenetic analyses support its placement within the class Caudoviricetes. No known lysogeny-associated genes, virulence factors, or antibiotic resistance genes were identified by genomic analysis. In vitro, BUCT980 markedly suppressed the growth of P. aeruginosa PAO1 across the tested multiplicities of infections (MOIs) and inhibited biofilm formation. In 10-fold serial-dilution spot assays, BUCT980 formed clear plaques on 4 of 29 clinical isolates and produced visible inhibition in 13 additional isolates representing multiple sequence types. In a murine model of acute P. aeruginosa pneumonia, intranasal administration of BUCT980 significantly improved survival, reduced pulmonary bacterial burden, and alleviated lung injury. No overt histopathological abnormalities were observed in the liver or kidney during short-term observation. These findings support further evaluation of BUCT980 as a candidate therapeutic phage for acute P. aeruginosa lung infection.IMPORTANCEPseudomonas aeruginosa is a major cause of difficult-to-treat respiratory infections because of its antibiotic resistance and biofilm-forming capacity. Here, we characterized BUCT980, a lytic phage that suppressed P. aeruginosa growth, inhibited early biofilm formation, and showed activity against clinical isolates from multiple sequence-type backgrounds. Genomic screening identified no known lysogeny-associated genes, virulence factors, or antibiotic resistance genes. In a murine acute pneumonia model, intranasal BUCT980 treatment improved survival, reduced pulmonary bacterial burden, and alleviated lung injury. Bacterial regrowth during prolonged exposure and limited activity against established biofilms indicate that combination strategies may be needed for sustained treatment. These findings support further preclinical evaluation of BUCT980 for acute P. aeruginosa lung infection.