P. aeruginosa biofilm infections: preclinical investigation of new treatment strategies based on the use of antimicrobial peptides

The present thesis focused on the optimization and preclinical development of the semi-synthetic peptide lin-SB056-1 as novel antimicrobial agent to treat P. aeruginosa biofilm-associated infections. Under low-salt conditions, such peptide was highly effective against antibiotic resistant strains and persister cells of P. aeruginosa. In addition, lin-SB056-1 used in combination with host compatible concentrations of the chelating agent EDTA significantly inhibited the formation of P. aeruginosa biofilm-like structures in an artificial sputum medium mimicking the lung environment of cystic fibrosis patients, and in the sputum from primary ciliary dyskinesia patients. The lin-SB056-1/EDTA combination was also able to exert a marked antibiofilm activity in an in vivo-like 3-D lung epithelial cell model replicating relevant aspects of in vivo chronic lung infections. Optimization of the peptide through the design of the dendrimeric derivative (lin-SB056-1)2-K resulted in an additional improvement of the antimicrobial properties both in the 3-D lung epithelial cell model and in an in vitro wound model. Overall, these findings confirmed that combination treatments and peptide dendrimerization represent promising strategies to improve the efficacy of AMPs, especially under in vivo-like conditions that greatly interfere with peptide activity. In particular, (lin-SB056-1)2-K emerged as a valuable lead in the development of new treatment strategies for P. aeruginosa infections.