Pathogenesis of bacterial bronchitis in cystic fibrosis

Abstract

To describe the current understanding of the pathogenesis of infections in cystic fibrosis (CF). The key element in the pathogenesis of infections in CF is the abnormal mucin resulting from a defective chloride channel. Abnormal mucin and the lack of hydration of respiratory secretions entraps bacteria, permitting colonization and subsequent infection. "Normal" physiologic insults, such as microaspiration, and pollution evoke mucin secretion with bacteria-mucin aggregates causing infection of small airways. Microcolonies of pulmotropic bacteria (i.e. Haemophilus and Staphylococcus) in the trapped mucin cause mucosal injury which predisposes the patient to Pseudomonas aeruginosa infection. Eventually there is obstruction of medium-sized and small airways by inflammatory exudate and mucus. Ultimately these chronic endobronchial bacterial infections cause significant loss of pulmonary function with morbidity and a decrease in the life span of patients with CF. Although antibiotic therapy is beneficial for the management of bacterial respiratory tract infections in CF patients, gene therapy may provide the ultimate cure. New treatment strategies will emerge as the pathogenesis of cystic fibrosis is better elucidated.