Characterization of bacteriophage BUCT631 lytic for K1 Klebsiella pneumoniae and its therapeutic efficacy in Galleria mellonella larvae

Severe infections caused by multidrug-resistant Klebsiella pneumoniae(K.pneumoniae)highlight the need for new therapeutics with activity against this pathogen.Phage therapy is an alternative treatment approach for multidrug-resistant K.pneumoniae infections.Here,we report a novel bacteriophage(phage)BUCT631 that can specifically lyse capsule-type K1 K.pneumoniae.Physiological characterization revealed that phage BUCT631 could rapidly adsorb to the surface of K.pneumoniae and form an obvious halo ring,and it had relatively favorable thermal stability(4–50C)and pH tolerance(pH?4–12).In addition,the optimal multiplicity of infection(MOI)of phage BUCT631 was 0.01,and the burst size was approximately 303 PFU/cell.Genomic analysis showed that phage BUCT631 has double-stranded DNA(total length of 44,812 bp)with a G t C content of 54.1%,and the genome contains 57 open reading frames(ORFs)and no virulence or antibiotic resistance related genes.Based on phylogenetic analysis,phage BUCT631 could be assigned to a new species in the genus Drulisvirus of the subfamily Slopekvirinae.In addition,phage BUCT631 could quickly inhibit the growth of K.pneumoniae within 2 h in vitro and significantly elevated the survival rate of K.pneumoniae infected Galleria mellonella larvae from 10%to 90%in vivo.These studies suggest that phage BUCT631 has promising potential for development as a safe alternative for control and treatment of multidrug-resistant K.pneumoniae infection.