Bacteriophage SRD2021 Recognizing Capsular Polysaccharide Shows Therapeutic Potential in Serotype K47 Klebsiella pneumoniae Infections

Abstract

Klebsiella pneumoniae is an opportunistic pathogen posing an urgent threat to global public health, and the capsule is necessary for K. pneumoniae infection and virulence. Phage-derived capsule depolymerases have shown great potential as antivirulence agents in treating carbapenem-resistant K. pneumoniae (CRKP) infections. However, the therapeutic potential of phages encoding depolymerases against CRKP remains poorly understood. In this study, we identified a long-tailed phage SRD2021 specific for mucoid CRKP with capsular K47 serotype, which is the predominant infectious K-type in Asia. Genome sequencing revealed that ΦSRD2021 belonged to the Drulisvirus genus and exhibited a capsular depolymerase domain in its tail fiber protein. A transposon-insertion library of host bacteria was constructed to identify the receptor for ΦSRD2021. We found that most phage-resistant mutants converted to a nonmucoid phenotype, including the mutant in wza gene essential for capsular polysaccharides export. Further knockout and complementation experiments confirmed that the Δwza mutant avoided adsorption by ΦSRD2021, indicating that the K47 capsular polysaccharide is the necessary receptor for phage infection. ΦSRD2021 lysed the bacteria mature biofilms and showed a therapeutic effect on the prevention and treatment of CRKP infection in the Galleria mellonella model. Furthermore, ΦSRD2021 also reduced the colonized CRKP in mouse intestines significantly. By recognizing the host capsule as a receptor, our results showed that ΦSRD2021 may be used as a potential antibacterial agent for K47 serotype K. pneumoniae infections.

Lytic Phages against ST11 K47 Carbapenem-Resistant Klebsiella pneumoniae and the Corresponding Phage Resistance Mechanisms

“…Only four phages have been previously described that can lyse ST11 K47 CRKP, SH-KP152226 ( 1 ), vB_KpnP_IME205 ( 11 ), SRD2021 ( 12 ), and P-KP2 ( 13 ). Among these four phages, phages SRD2021 and P-KP2 belong to the family Siphoviridae and Myoviridae , respectively.…”

“…Novel phages are required as the prerequisite for cocktails to overcome phage resistance during therapy. Only four phages have been reported in the literature as able to lyse ST11 K47 CRKP, SH- KP152226 ( 1 ), vB_KpnP_IME205 ( 11 ), SRD2021 ( 12 ), and P-KP2 ( 13 ). We isolated and characterized a novel phage able to lyse ST11 K47 CRKP, expanding the repertoire of phages against CRKP.…”

A Combination of Virulent and Non-Productive Phages Synergizes the Immune System against Salmonella Typhimurium Systemic Infection

“…For measuring lysis activity of the phages against Salmonella strains, stationary cultures (10 8 CFU/mL) were mixed with phages or phage combination at different MOIs (multiplicities of infection) in 96-well plates and incubated at 37 °C in a standing condition. Growth curves were monitored by measuring the optical density at 600 nm (OD 600 ) at 10-min intervals for 6 h. The one-step growth curve of a phage and the frequency of phage-resistant mutants for strain ST149 were measured as described previously, with a slight modification [ 36 , 37 ]. Briefly, to determine the rate of mutation of S. Typhimurium ST149 to phages, approximately 10 8 CFU of overnight bacterial cells were infected with phages at an MOI of 1 at 37 °C, 180 rpm for 2 h, then the cultures were centrifuged and the pelleted cells were resuspended with SM buffer containing 10 8 PFU of corresponding phages.…”

Isolation and characterization of bacteriophages against IMP-6-producingKlebsiella pneumoniaeisolated from clinical settings in Japan

“…SNP analysis of Kp21 and Kp21r revealed that insertion mutations occurred in at least two genes; cpsA, encoding putative capsular biosynthesis (30). A recent article reports a novel phage that recognizes the capsular polysaccharide of K. pneumoniae (31), and accordingly, we speculate that capsular polysaccharide is one of the factors allowing øKp_21 to adsorb to its host Kp21. We found that Myoviridae, in the phage cocktail, diminished the lawn density of Kp21r on the plates.…”