Genomic analysis and therapeutic efficacy evaluation of bacteriophage PK2420 for pneumonia caused by hypervirulent <i>Klebsiella pneumoniae</i> (K20 serotype)

Hypervirulent <i>Klebsiella pneumoniae</i> (hvKp) strains are increasingly recognized for their aggressive nature, which leads to severe clinical outcomes. The emergence of multidrug-resistant strains constitutes a substantial challenge for clinical management. Phage therapy offers a potential solution to the antibiotic resistance crisis. A multidrug-resistant hvKp strain, K2420 (K20 serotype), was used to isolate bacteriophages from hospital sewage. Phage morphology, biological properties, and genome characteristics were analyzed using transmission electron microscopy, plaque assays, and whole-genome sequencing. Therapeutic safety and efficacy were assessed in an acute pneumonia murine model induced by intratracheal injection of K2420. Assessment parameters included bacterial load, phage titer, body temperature, cytokine levels, histopathological findings, and other relevant indicators. Phage PK2420, a member of the <i>Autographiviridae</i> family and <i>Przondovirus</i> genus, was identified. It rapidly lyses <i>K. pneumoniae</i> (K20 serotype), inhibits biofilm formation, and exhibits a burst size of 37.4 plaque-forming units/cell. The phage is stable at temperatures ranging from 0°C to 40°C and pH values between 6 and 9. Its genome, 41,155 bp in length, contains 46 coding sequences. The phage has no genes associated with antibiotic resistance, virulence, or lysogeny. <i>In vivo</i>, PK2420 substantially reduced <i>K. pneumoniae</i> bacterial loads, improved survival rates, and alleviated pneumonia severity without observable side effects. Phage PK2420 exhibits lytic activity against <i>K. pneumoniae</i> both <i>in vitro</i> and in murine models, providing a promising and safe option for the treatment of hvKp infections.IMPORTANCEOur investigation provides insights into the interaction mechanism among hypervirulent <i>Klebsiella pneumoniae</i> (hvKp) (K20 serotype), phage, and the host in a mouse pneumonia model, offering a valuable reference for future research on phage pharmacokinetics. This study demonstrated that bacteriophage PK2420 exhibits promising biosafety and therapeutic efficacy against hvKp-induced pulmonary infections and dissemination in a murine model. These findings suggest that phage PK2420 may be a potential option for the clinical treatment of hvKp infections.