A Novel Genus of Virulent Phage Targeting Acinetobacter baumannii : Efficacy and Safety in a Murine Model of Pulmonary Infection

Acinetobacter baumannii ( A.baumannii ) is a notable opportunistic pathogen responsible for severe hospital-acquired infections, with multidrug-resistant strains posing significant treatment challenges. Phage therapy, which employs bacteriophages as natural bacterial antagonists, has gained renewed attention as a promising solution to combat antibiotic-resistant infections. In this study, we isolated and characterized a novel virulent phage, vB_AbaS_qsb1, which specifically lyses A.baumannii . Phylogenetic and genomic analyses indicate that vB_AbaS_qsb1 is the founding member of a previously unreported genus, which we have named as Acinibactriovirus , with Acinibactriovirus lysinus as the type species. vB_AbaS_qsb1 demonstrated robust stability across diverse temperature and pH ranges, a short latent period, and no known virulence or antibiotic resistance genes within its 54,713 bp dsDNA genome. Safety assessments showed that high-dose vB_AbaS_qsb1 induced no adverse effects in mice, with histopathology confirming its safety profile. Therapeutic experiments further indicated that vB_AbaS_qsb1 provided at least 50% protection against A.baumannii -induced pneumonia, significantly reducing bacterial loads and inflammation markers, while maintaining high phage titers in lung tissue.This study introduces vB_AbaS_qsb1 as a promising candidate for phage therapy against A.baumannii , offering both innovative insights and a valuable framework for future isolation, genomic characterization, and efficacy evaluation of phages targeting antibiotic-resistant bacteria.