Biological Characterization Of Bacteriophage BUCT541 And Studies On Its Treatment Of Klebsiella Pneumoniae Infection

In recent years,antibiotic abuse has caused concern about multi-drug resistant bacteria infections such as Klebsiella pneumoniae(K.pneumoniae).Bacteriophages are considered as one of the most promising alternative candidates owing to their abundance and low toxic effects for humans.In this study,a phage which specifically lysed K.pneumoniae K1-ST23was obtained from hospital sewage and named as BUCT541.The latent period of phage BUCT541 was about 30 min and its burst size was 227 PFU/cell at the optimal MOI.The titer of phage BUCT541 did not decrease significantly in the p H range of 3～11 and the temperature range of 4℃～60℃.The excellent stability and high burst size provide possibilities for the storage and transportation of phage BUCT541,as well as future related product applications.The next-generation sequencing data showed that the whole genome of phage BUCT541 was 46,100 bp with 48%GC content.A total of78 open reading frames(ORFs)and three t RNA were predicted,no virulence protein-related genes were predicted in the genome of phage BUCT541.Phylogenetic trees were constructed based on the whole genome sequence,large terminase and capsid protein’s amino acid sequences of phage BUCT541,and the results indicates that BUCT541 most closely related to the K.pneumoniae phage v B＿Kpn S＿ZX4,and also closely related to the Vibrio phage p YD38-A.In vivo treatment results showed that BUCT541[4×10~5plaque forming units(PFU)/each]significantly increased the survival rate of Galleria mellonella which were infected K.pneumoniae S-2007[4×10~5colony-forming units(PFU)/each]for 30 min from 5%to 83%within 48 hours.Moreover,BUCT541(2×10~7PFU/each)could completely prevent BALB/c mice from death when challenged by intranasal K.pneumoniae S-2007(2×10~6CFU/each)6 hours post infection and significantly reduced the proliferation of K.pneumoniae in the lungs,as well as improved pathological symptoms in the lungs such as multifocal hemorrhage and inflammation and so on.In conclusion,a multi-drug resistant K.pneumoniae phage BUCT541was isolated in this study,biological characterization study showed it has a good stability,and no virulence related gene was identified by whole-genome sequencing analysis.Galleria mellonella and BALB/c infection models demonstrated that BUCT541 has good treatment effect on K.pneumoniae infection in vivo.Our study lays a foundation for the clinical treatment of K.pneumoniae infections by phage BUCT541.