Abstract
BACKGROUND: Carbapenem-resistant Klebsiella pneumoniae (CRKP), a major nosocomial pathogen, poses an increasingly serious threat to human health. RESULTS: In the quest for innovative therapeutic modalities to treat CRKP infections, a newly discovered phage, vB_KpnM_JYSS3, which can specifically infect and lyse K2-type CRKP, was isolated and subjected to an array of comprehensive characterizations and genome sequencing. Furthermore, an analysis of the expression of the tail protein (ORF17) and the detection of its functions were carried out. Double-layer agar plates containing CRKP were used to isolate phages from hospital sewage samples. The phage's optimal multiplicity of infection (MOI), lytic spectrum, bactericidal activity, stability, and one-step growth curve were tested. The biofilm development ability of the CRKP strain 21AA2216 and the phage antibiofilm activity were determined using a 96-well microtitration plate. vB_KpnM_JYSS3 prevented biofilm generation and broke down mature biofilms. The whole-genome sequencing results revealed that vB_KpnM_JYSS3 is a toxic phage (nontemperate). The genome size of vB_KpnM_JYSS3 is 47,244 bp, and the G + C content is 48.48 mol%. A total of 71 coding sequences (CDSs) were predicted. Protein function prediction revealed that the tail protein (ORF17) of vB_KpnM_JYSS3 may possess depolymerase activity, consistent with the halo phenomenon around the plaque. ORF17 was expressed, purified, and named Dep17. Dep17 can degrade the capsular polysaccharide (CPS) surrounding K2-type CRKP, and it can also enhance the activity of polymyxin B against K2-type CRKP biofilms. CONCLUSIONS: Phage vB_KpnM_JYSS3 and its novel depolymerase Dep17 may represent promising strategies for combating infections resulting from biofilm-forming and drug-resistant K2-type CRKP.