Characterization and therapeutic efficacy of phage p9676 against epidemic ST11-KL64 Klebsiella pneumoniae: Insights from genomic analysis and in vivo studies

Introduction: Klebsiella pneumoniae presents a formidable challenge in clinical settings due to its increasing resistance to last-line antibiotics like carbapenem, tigecycline, and colistin, raising global concerns. An emerging alternative strategy involves harnessing bacteriophages to combat infections caused by multidrug-resistant bacteria. Methods and results: In this study, we isolated the bacteriophage p9676 from hospital sewage and demonstrated its ability to lyse K. pneumoniae strains with ST11-KL64 capsular type. Transmission electron microscopy and genomic analysis identified p9676 as a member of the Caudoviricetes class, Autographiviridae family, with a double-stranded DNA genome of 41,095 base pairs and a GC content of 52 %. The genome contains 53 coding DNA sequences (CDSs) and lacks tRNA, virulence, or antibiotic resistance genes. Notably, p9676 exhibited a short latent period of only 5 min and an optimal multiplicity of infection (MOI) of 0.0001. In vivo studies further demonstrated that p9676 effectively treated ST11-KL64 K. pneumoniae-infected mice, significantly reducing the blood bacterial load compared to untreated controls. Genomic analysis also revealed that resistance to p9676 was associated with a disruption in the capsule synthesis gene wcaJ caused by the insertion sequence ISKpn26. Conclusion: Our findings underscore the effectiveness of phage p9676 therapy in combating epidemic ST11-KL64 K. pneumoniae infections, highlighting its potential as a promising treatment option.