Cystic fibrosis (CF) manifests as a clinical syndrome characterized by chronic sinopulmonary infection as well as by gastrointestinal, nutritional, and other abnormalities. Cystic fibrosis (CF) lung disease is characterized by airway obstruction, chronic bacterial infection, and a vigorous host inflammatory response. Antibiotic therapy of bacterial lung infections has tremendously contributed to the increased survival in CF. However, many bacteria form biofilms in the CF lung that make their eradication difficult. A relatively limited number of bacteria are involved in lung infections and the prevalence of different pathogens varies according to the patient’s age, being usually represented by Staphylococcus aureus in young children and by Pseudomonas aeruginosa (Pa) thereafter. Lung damage secondary to chronic infection is the main determinant of morbidity and mortality in individuals with cystic fibrosis (CF). CF individuals are highly susceptible to bacterial infections in the respiratory tract and repeated and intensive antibiotic therapy is required to maintain lung function and quality of life and reduce exacerbations in infected patients.