# A capsule-dependent lytic phage for targeting multidrug-resistant and hypervirulent Klebsiella pneumoniae

## TL;DR

This study introduces a phage called phiK2044 that effectively targets dangerous, drug-resistant Klebsiella pneumoniae strains and works well in mice without harmful side effects.

## Contribution

The discovery of phiK2044, a lytic phage with high specificity for hypervirulent K. pneumoniae and a novel wcaJ-dependent binding mechanism.

## Key findings

- PhiK2044 showed strong efficacy against hypervirulent K. pneumoniae subtypes in both in vitro and in vivo models.
- The phage binds to the host via the wcaJ gene, which is essential for capsular synthesis.
- PhiK2044 safely cleared bacterial infections in mice without significant side effects.

## Abstract

As the threat of multidrug-resistant Klebsiella pneumoniae strains rises, the potential of phages as promising alternatives to antibiotics is increasingly being demonstrated. In this study, we isolated and characterized phiK2044, a highly specific and efficient lytic phage targeting the model strain K. pneumoniae NTUH-K2044. Demonstrating wide host compatibility, potent lytic activity, and robust environmental adaptability, phiK2044 exhibited exceptional efficacy against hypervirulent subtypes, including hypervirulent K. pneumoniae (45.2%), sequence type 23 (87.5%), and capsular K1 (92.3%). In the mouse model, phiK2044 effectively cleared bacteria without significant side effects, highlighting its therapeutic potential. Mechanistically, we identified wcaJ, a gene encoding a glycosyltransferase essential for capsular synthesis, as the critical determinant of the binding of phiK2044 to the host. Beyond its clinical utility, phiK2044 represents a model for studying phage ecology, host–microbe interactions, and capsule-dependent tropism. Collectively, phiK2044 represents a valuable tool against ST23/K1 K. pneumoniae infections, such as liver abscesses and bacteremia.

The rise of multidrug-resistant Klebsiella pneumoniae demands innovative therapies. This study identifies phiK2044, a lytic phage with high specificity and efficacy against hypervirulent subtypes. It safely clears infections in mice and reveals wcaJ-dependent capsule synthesis as the key host interaction mechanism. Beyond its therapeutic promise, phiK2044 serves as a critical tool for studying phage-host dynamics and capsule-mediated tropism, bridging clinical solutions and fundamental research in combating antimicrobial resistance.