Regional differences in infection and structural lung disease in infants and young children with cystic fibrosis.

Background: Both infection and inflammation are critical to the progression of cystic fibrosis (CF) lung disease. Potential anatomical differences in lower airway infection, inflammation and bronchiectasis in young children with CF raise questions regarding the pathogenesis of early structural lung disease.

Methods: A longitudinal multi-centre birth cohort study of infants newly diagnosed with CF was conducted. Paired bronchoalveolar lavage (BAL) samples were obtained from the right middle lobe (RML) and lingula bronchi. Chest computed tomography (CT) was performed biennially and analysed using the modified CF-CT scoring system.

Results: One hundred and twenty-four children (0.11 - 7.0 years) contributed 527 BAL samples and underwent 388 CT chest scans. Pro-inflammatory microbes were detected in 279 BAL samples (53%), either in both lingula and RML samples (69%), in the lingula alone (24%), or in the RML alone in only 7% of samples. Overall, the prevalence of structural lung disease was greater in the setting of pro-inflammatory microbes. Although infection was less commonly isolated in the right lung, bronchiectasis was more commonly detected in the right lung compared with the left. No anatomical differences in the presence of air trapping were detected.

Conclusion: Overall, the detection of pro-inflammatory microbes in the lower airways was associated with increased risk of both air trapping and bronchiectasis. However, the apparent discordance between commonest sites of isolation of pro-inflammatory microbes and the anatomical site of early bronchiectasis warrants further exploration.