80 The microbiome in early cystic fibrosis lung disease: A longitudinal analysis

Objectives

The evolution of the respiratory microbiome in CF and its contribution to the development of lung disease is yet to be characterised. The few longitudinal studies in older patients suggest a decrease in microbial diversity over time, possibly occurring in conjunction with declining pulmonary function.

This study describes the lower airway microbiome in CF and its evolution in early childhood. We aim to assess the correlation between the microbiome, traditional culture-based microbiology and inflammatory status, and to examine the impact of the early lung microbiome on pulmonary function at six years of age.

Methods

Serial surveillance bronchoscopies were performed on newly diagnosed infants with CF in 1992–2001. Quantitative bacterial culture and inflammatory markers (cell count, IL-8 and neutrophil elastase) were performed contemporaneously. 16S rDNA analysis was performed on stored samples.

Results

16S rDNA analysis was successfully performed on serial BAL samples from 18 infants (77% P.Phe508del homozygous, 50% male). Samples were obtained at median ages of 2.8 months (range 1.2–27.3), 15.2 months (range 12.3–39.7), 27.5 months (range 20.4–78.3) and 46.7 months (range 28.4–63.6). Microbial diversity decreased over time, with increasing dominance of traditional CF pathogens, particularly staphylococcal and Pseudomonas species. There was often concordance between culture results and the dominant species on 16S analysis.

Conclusion

16S rDNA analysis of these historical BAL samples provides a unique insight into the early lung microbiome in CF, its evolution over time and its correlation with long term clinical outcomes.