Identification of multi-drug resistant Acinetobacter baumannii phage YZ2 and evaluation of its therapeutic efficacy in vivo and in vitro.

Introduction: Carbapenem-resistant Acinetobacter baumannii (CRAB) has recently become an important pathogen in clinically acquired infections, making treatment more challenging. Methods: The treatment of bacterial infections may improve with the development of phage therapy and phage-antibiotic combination therapy. Here, we reported a novel phage YZ2 that has a double-stranded DNA genome of 40,181 bp with 37.93% GC content. A total of 46 open reading frames (ORFs) and no virulence or antimicrobial resistance genes were annotated in the genome of phage YZ2. Phage YZ2 is a novel member of the Autographiviridae, with a latency period of approximately 20 min and a burst size of approximately 134 phage particles per infected host cell. Results: The in vitro antibacterial results demonstrated that YZ2 could rapidly eliminate host bacteria at a low multiplicity of infection, showing strong bactericidal efficacy. In vivo, YZ2 significantly increased the survival rate of A. baumannii-infected Galleria mellonella larvae from 10 to 100% within 72 h. Discussion: Moreover, compared with the use of phage or polymyxin B alone, the combined use of phage YZ2 and polymyxin B can significantly increased the survival rate of G. mellonella larvae and had a synergistic effect. These results imply that phage YZ2 has the potential for development as an antimicrobial agent.