PROJECT SUMMARY The Infectious Diseases Society of America recently identified a list of antibiotic-resistant pathogens that can escape the effect of most antimicrobial agents. These problematic pathogens include Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp., which are collectively abbreviated as ESKAPE. Therefore, there is an urgent need to develop effective antibiotics to keep up with antibiotic resistance. Paenipeptins are novel synthetic linear lipopeptides, which are made of 9 amino acid residues and a fatty acyl group at the N-terminus. They showed highly potent activity in combination with clarithromycin against Gram- negative pathogens in vitro. The overall goal of this project is to develop novel linear lipopeptide antibiotic potentiators, which can be co-administered with FDA-approved antibiotics, to expand their antimicrobial spectrum and enhance the antibiotic activity for the treatment of infections associated with polymyxin-resistant and carbapenem-resistant pathogens. To achieve this goal, the following two aims are set. Aim 1: Evaluate the synergistic effect between paenipeptin analogues and clarithromycin in vitro against a large number of carbapenem-resistant clinical isolates and investigate the mechanism of synergism. Aim 2: Develop antimicrobial-loaded hydrogels for localized delivery of paenipeptin-clarithromycin mixture for topical treatment of wound infections.