Tryptophan-substituted antimicrobial peptide temporin-1CEb: in vitro and in vivo antibacterial activity against clinically isolated multidrug-resistant Klebsiella pneumonia

• Trp-substituted temporin-1CEb analogs (I4W, I1WL5W) show enhanced antibacterial activity against multidrug-resistant Klebsiella pneumoniae with lower cytotoxicity than L12W. • The peptides act by neutralizing bacterial surface charge, inserting into membranes, increasing permeability of inner/outer membranes, and disrupting membrane integrity; I1WL5W is the most potent. • Trp-containing peptides inhibit biofilm formation and degrade preformed biofilms, targeting exopolysaccharide production. • In a murine lung infection model, I1WL5W reduces bacterial load and inflammatory cytokines (IL-6, TNF-α) and improves lung tissue structure, highlighting therapeutic potential.