Data were shown demonstrating that level of P. aeruginosa infection is controlled by host genetic diversity which impact on disease severity. A significant locus was mapped on chromosome 3 and was named Pseudomonas respiratory infection resistant locus. Within this genetic locus 14 candidates genes, including those related to host defense and immunity, were ranked and considered as promising candidates gene modifiers for validation. These new informations might be translated into human CF population and represent predictive factors of clinical outcome in CF patients.