PepW is a potent antimicrobial peptide targeting the capsule of multidrug-resistant Klebsiella pneumoniae, with a minimum inhibitory concentration (MIC) of 2-8 μM. It exerts its bactericidal effect by aggregating and disrupting the structure of capsule polysaccharides. PepW holds promise for research into infectious diseases caused by Gram-negative bacteria, such as pneumonia and sepsis.