Characterization of a Lytic Bacteriophage and Demonstration of Its Combined Lytic Effect with a K2 Depolymerase on the Hypervirulent Klebsiella pneumoniae Strain 52145

Abstract

Klebsiella pneumoniae is a nosocomial pathogen. Among its virulence factors is the capsule with a prominent role in defense and biofilm formation. Bacteriophages (phages) can evoke the lysis of bacterial cells. Due to the mode of action of their polysaccharide depolymerase enzymes, phages are typically specific for one bacterial strain and its capsule type. In this study, we characterized a bacteriophage against the capsule-defective mutant of the nosocomial K. pneumoniae 52145 strain, which lacks K2 capsule. The phage showed a relatively narrow host range but evoked lysis on a few strains with capsular serotypes K33, K21, and K24. Phylogenetic analysis showed that the newly isolated Klebsiella phage 731 belongs to the Webervirus genus in the Drexlerviridae family; it has a 31.084 MDa double-stranded, linear DNA with a length of 50,306 base pairs and a G + C content of 50.9%. Out of the 79 open reading frames (ORFs), we performed the identification of orf22, coding for a trimeric tail fiber protein with putative capsule depolymerase activity, along with the mapping of other putative depolymerases of phage 731 and homologous phages. Efficacy of a previously described recombinant K2 depolymerase (B1dep) was tested by co-spotting phage 731 on K. pneumoniae strains, and it was demonstrated that the B1dep-phage 731 combination allows the lysis of the wild type 52145 strain, originally resistant to the phage 731. With phage 731, we showed that B1dep is a promising candidate for use as a possible antimicrobial agent, as it renders the virulent strain defenseless against other phages. Phage 731 alone is also important due to its efficacy on K. pneumoniae strains possessing epidemiologically important serotypes.

Relationship between biofilm formation and antibiotic resistance of Klebsiella pneumoniae and updates on antibiofilm therapeutic strategies

“…Li et al isolated a lytic phage P510 from K. pneumoniae KL64 and characterized a specific phage-derived depolymerase with polysaccharide-degrading activity and significant antibiofilm effect, which had the same lysis spectrum as phage P510 (Li M. et al, 2021). Bacteriophage KpV74 and phage depolymerase Dep_kpv74 are specific to lyse hypervirulent K. pneumoniae of the K2 capsular type, and the depolymerase Dep_kpv74 was effective against K. pneumoniae infection in mice thigh soft tissue, with comparable or greater efficiency than that of the bacteriophage (Pertics et al, 2023).…”

New Strategies to Kill Metabolically-Dormant Cells Directly Bypassing the Need for Active Cellular Processes

“…The most promising and most effective are combinations of phage-derived depolymerases with BCWH or phages with bacterial cell wall lytic activity. Pertics et al demonstrated that the combination of bacteriophage B1 and depolymerase K2 (B1dep) [ 170 ] leads to cell lysis of the hypervirulent strain K. pneumoniae 52145, which was initially resistant to phage 731 alone [ 171 ]. The B1dep depolymerase specifically degrades the K2 capsule enabling the B1 phage to degrade peptidoglycan and induce cell lysis.…”