New anti-infective therapies are urgently needed for the treatment of drug-resistant bacterial infections in the context of the rapid spread of drug resistance. Phages, the natural enemies of bacteria, have irreplaceable advantages in the treatment of bacterial infections. Here, we report a novel phage, vB_KpnP_Henu1_3, that specifically lyses capsule-type K1 Klebsiella pneumoniae . The phage vB_KpnP_Henu1_3 shows relatively favorable thermal stability (4°C–55°C) and pH tolerance (pH = 4–11). In addition, the optimal multiplicity of infection is 0.01, with a burst size of approximately 253 ± 54 PFU/cell. Genomic analysis reveals that phage vB_KpnP_Henu1_3 contains double-stranded DNA (total length of 49,808 bp) with a G + C content of 50.76%, and the genome comprises 75 open reading frames with no virulence- or antibiotic resistance-related genes. Transmission electron microscopy observations revealed that phage vB_KpnP_Henu1_3 possessed an icosahedral head and siphovirus morphology. Based on the genome sequence, phage vB_KpnP_Henu1_3 could be assigned to a new species in the genus Webervirus of the family Drexlerviridae . Furthermore, phage vB_KpnP_Henu1_3 rapidly inhibits the growth of K. pneumoniae within 4 h, prevents biofilm formation, and disrupts mature biofilms in vitro . In infection animal models, phage vB_KpnP_Henu1_3 significantly increases the survival rate of K. pneumoniae -infected Galleria mellonella larvae and mice while reducing the bacterial loads. These findings demonstrate that phage vB_KpnP_Henu1_3 has promising potential as a safe alternative for controlling and treating multidrug-resistant K1-type K. pneumoniae infections. IMPORTANCE: The widespread use of antibiotics has led to increasing antibiotic resistance, which is a growing global health concern. Therefore, the development of novel antimicrobial therapy that can cure drug-resistant bacteria-induced infections is imperative. Phages are of increasing interest as natural enemies of bacteria with clear advantages in antibacterial.

Background: Ceftazidime-avibactam (CZA) is a key treatment for carbapenem-resistant Klebsiella pneumoniae (CRKP), but resistance is emerging rapidly in China. Henan is a CRKP epicenter, yet the genomic drivers of CZA resistance remain unclear. Methods: We conducted a multicenter genomic epidemiology study of 109 non-duplicate CZA-R-CRKP isolates collected from 12 hospitals in Henan between October 2020 and April 2025. Whole-genome sequencing (WGS) was used to resolve population structure, carbapenemase genotypes, predicted plasmid contexts, hypervirulence-associated markers, porin variants, and genomic clusters suggestive of possible transmission. Results: ST11 predominated among the CZA-R-CRKP isolates (66.1%, 72/109) and accounted for nearly all isolates carrying bla _KPC alone or with bla _NDM (95.9%, 71/74), including most KPC + NDM co-producers. The proportions of carbapenemase genotypes differed across the sampled collection periods, with a higher proportion of KPC-containing genotypes in later periods; this descriptive pattern is not a population-level temporal trend. Phylogenomic analysis identified genomic clusters suggestive of possible transmission, including a neonatal-ward cluster of ST20-KL38- bla _NDM-1 isolates. Seventy-two isolates carried at least one of five hypervirulence-associated markers, and this marker carriage was more frequent in bla _KPC -containing groups than in the bla _NDM -only group. Plasmid profiling showed that bla _KPC was mainly associated with MOB-suite-predicted AA032-type plasmid clusters, whereas bla _NDM was assigned to more heterogeneous predicted backbones. We identified a KPC variant, KPC-291, harboring dual catalytic-loop alterations (D179Y and G239_V240del), and an OmpK35 deletion variant frequently observed among bla _KPC-2 -only isolates; these co-occurrence patterns were descriptive and not evidence of a functional interaction. Conclusions: In this hospital-based collection, CZA-R-CRKP was dominated by ST11 lineages carrying bla _KPC and hypervirulence-associated markers. The findings also show carbapenemase diversification, recurrent OmpK35 remodeling, and diverse predicted plasmid profiles; the genomic clusters and KPC-291 require further epidemiological and functional validation.

Objective: Given the limited therapeutic options for infections caused by carbapenem-resistant Klebsiella pneumoniae (CRKP) due to multidrug resistance, this study aimed to evaluate combination therapeutic strategies based on carbapenemase profiles and resistance phenotypes. Methods: The in vitro activities of ceftazidime-avibactam (CZA) and polymyxin B (PMB)-based combinations was systematically evaluated against 139 CRKP isolates, including K. pneumoniae carbapenemase (KPC) producing strains, New Delhi metallo-β-lactamase (NDM), and KPC and NDM co-producing carbapenem-resistant K. pneumoniae strains (KN-CRKP). The combination effects of these antimicrobial combinations were assessed using the fractional inhibitory concentration index (FICI) and susceptibility breakpoint index (SBPI). Results: Among CZA-resistant KPC-CRKP isolates, combinations of CZA with β-lactams exhibited high synergy rates (79.7-86.5%). In PMB-resistant KPC-CRKP, PMB + CZA demonstrated substantially higher synergy rates (53.2%) than conventional PMB-carbapenem combinations (≤3.8%). Against NDM-CRKP, CZA + aztreonam (ATM) showed synergistic activity in 83.3% of isolates. Notably, in KN-CRKP, CZA + ATM produced synergistic or additive effects in all isolates, despite resistance to the individual agents. SBPI analysis further suggested substantial antimicrobial enhancement in some combinations classified as indifferent by FICI, including PMB + tigecycline (TGC). Conclusions: Carbapenemase profiles substantially influence the efficacy of combination therapies against CRKP. CZA-based combinations, particularly those combined with β-lactams or ATM, demonstrated favorable in vitro activity against KPC and NDM-producing CRKP, while PMB in combination with CZA partially restored activity in PMB-resistance isolates. Notably, the CZA-ATM regimen showed consistently favorable activity against both NDM-CRKP and KPC-NDM co-producing isolates. These findings support the potential value of carbapenemase profile-guided combination therapy for optimizing treatment of highly resistant CRKP infections.