Introduction: The COPD bacteriome associates with disease severity, exacerbations, and mortality. While COPD patients are susceptible to fungal sensitisation, the role of the fungal mycobiome remains uncertain.
Methods: We report the largest multicenter evaluation of the COPD airway mycobiome to date including participants from Asia (Singapore and Malaysia) and the United Kingdom (Scotland) when stable (n=337) and during exacerbations (n=66) as well as non-diseased controls (n=47). Longitudinal mycobiome analyses performed during and following COPD exacerbations (n=34) were examined in terms of exacerbation frequency, two-year mortality, and the occurrence of serum specific-IgE against selected fungi.
Results: A distinct mycobiome profile is observed in COPD compared to controls evidenced by increased alpha diversity (Shannon-index) (p<0.001). Significant airway mycobiome differences including greater inter-fungal interaction (by co-occurrence) characterise very frequent COPD exacerbators (≥3 exacerbations per year) (PERMANOVA, adjusted p<0.001). Longitudinal analyses during exacerbations and following treatment with antibiotics and corticosteroids did not reveal any significant change in airway mycobiome profile. Unsupervised clustering resulted in two clinically distinct COPD groups, (1) with increased symptoms (CAT score) and Saccharomyces dominance and (2) with very frequent exacerbations and higher mortality characterised by Aspergillus, Penicillium and Curvularia with a concomitant increase in serum specific IgE levels against the same fungi. During acute exacerbations of COPD, lower fungal diversity associates with higher two-year mortality.
Conclusion: The airway mycobiome in COPD is characterised by specific fungal genera associated with exacerbations and increased mortality.