The researchers isolated new phages able to infect P. aeruginosa and characterized their ability to grow on a large number of Italian P. aeruginosa clinical strains, isolated from CF patients. Six phages were mixed in a cocktail. The genome sequence of the six phages excluded the presence of genes undesired for phage therapy, such as genes encoding toxins or lysogenic functions. The ability of the phage cocktail to eliminate P. aeruginosa infections in vivo was tested. Two different in vivo animal models were compared: acute respiratory infection in mouse and bacteremia in Galleria mellonella larvae. In both model bacterial infection can be counteracted by administration of the phage cocktail. Survival of mice was recovered at 100%, whereas in Galleria larvae a significant delay in lethality was observed. The use of the Galleria model was extended to infections caused by clinical strains, including MDR, chronic and mucoid strains. Furthermore, administration of the phage cocktail to larvae prior to bacterial infection provided prophylaxis. These results forward the perspective that phage therapy could be a valid treatment option against Pa infections in CF.