Staphylococcus aureus is one of the first pathogens to colonize the lungs of CF patients. It may be possible that S. aureus causes lesions and patho-physiological changes to the infected lungs, thus acting as a gateway organism that paves the way for colonization by P. aeruginosa. Therefore, early anti-S. aureus treatment may affect chronic lung disease progression. With the aim to explore this hypothesis, researchers will set up eradication protocols of S. aureus infection in murine model of chronic airways infection and establish the impact of S. aureus treatment on restoring lung physiology. The same murine model will be then superinfected with P. aeruginosa. The benefit of S. aureus treatment on subsequent P. aeruginosa colonization will be established analysing infection, inflammation and lung damage. Understanding how S. aureus treatment may impact on subsequent P. aeruginosa colonization will provide new hints on how clinicians should manage CF patients infected with S. aureus.