Isolation and characterization of Klebsiella pneumoniae bacteriophages encoding polysaccharide depolymerases with rare capsule specificity

Bacterial infections caused by antibiotic resistant strains of Klebsiella pneumoniae are among the most dangerous threats for the world's public healthcare. Treatment with bacteriophages and/or their derivatives could become one of the alternative methods for therapy of infections caused by K. pneumoniae. The study was aimed to isolate from the environment and characterize the capsule-specific K. pneumoniae bacteriophages that are useful for therapy and possess the polysaccharide depolymerase genes. Bacteriophages were isolated from the river water samples by enrichment method. The host range of bacteriophages were assessed using the collection of 180 K. pneumoniae clinical strains. Bacteriophage whole genome sequencing was performed on the MiSeq platform (Illumina). Four new bacteriophages from different taxonomic groups were isolated and characterized during the study: vB_KpnM_NDO71 (Vequintavirinae family), vB_KpnS_MAG26fr (Casjensviridae family), vB_KpnS_MDA2066 (Ackermannviridae family), and vB_KpnS_PMM-G3 (Drexlerviridae family). Bacteriophages vB_KpnM_NDO71, vB_KpnS_MAG26fr, and vB_KpnS_PMM-G3 had a narrow lytic spectrum and lysed all strains with the capsular type of the host: KL45, KL19 or KL28, respectively. Bacteriophage vB_KpnS_MDA2066 showed lytic activity against strains with two different capsular types: KL19 and KL107. Bacteriophages were strictly virulent and contained no integrase genes, potentially dangerous toxin genes or antibiotic resistance determinants. This allows them to be used in therapeutic practice. Receptor-binding proteins represented by polysaccharide depolymerases were predicted for each bacteriophage.