Changing Prevalence of Lower Airway Infections in Young Children with Cystic Fibrosis.

Rationale: Historical studies suggest that airway infection in cystic fibrosis initiates with Staphylococcus aureus and Haemophilus influenzae, with later emergence of Pseudomonas aeruginosa. Aspergillus species are regarded as relatively infrequent, late-occurring infections.Objectives: To assess the prevalence and change in prevalence of early lower airway infections in a modern cohort of children with cystic fibrosis.Methods: All infants diagnosed with cystic fibrosis after newborn screening participating in the Australian Respiratory Early Surveillance Team for Cystic Fibrosis (AREST CF) cohort study between 2000 and 2018 were included. Participants prospectively underwent BAL at 3-6 months, 1 year, and annually up to 6 years of age. Lower airway infection prevalence was described. Changes in prevalence patterns were assessed longitudinally using generalized estimating equations controlling for age and repeated visits.Measurements and Main Results: A total of 380 infants underwent 1,759 BALs. The overall prevalence and median age of first acquisition of the most common infections were as follows: S. aureus, 11%, 2.5 years; P. aeruginosa, 8%, 2.4 years; Aspergillus species, 11%, 3.2 years; and H. influenzae, 9%, 3.1 years. During the study, a significant decrease in prevalence of P. aeruginosa (P < 0.001) and S. aureus (P < 0.001) was observed with a significant change toward more aggressive treatment. Prevalence of Aspergillus infections did not significantly change (P = 0.669).Conclusions:Aspergillus species and P. aeruginosa are commonly present in the lower airways from infancy. The decrease in prevalence of P. aeruginosa and S. aureus since 2000, coinciding with a more aggressive therapeutic approach, has resulted in Aspergillus becoming the most commonly isolated pathogen in young children. Further research is warranted to understand the implication of these findings.