LSC Abstract – Functional metagenomics of respiratoy microbiome in exacerbated COPD

Background: The course of COPD is frequently aggravated by exacerbations. New molecular techniques have suggested that many bacterial groups, not only the common COPD pathogens, could trigger the exacerbations. Objective: to analyze the microbial community and the gene content of samples obtained during stability and exacerbation of COPD patients. Method: 16S rRNA was pyrosequenced to obtain the taxonomic information. The metabolic information was obtained with the Metagenomics RAST server (MG-RAST) with KEGG database. Results: 8 severe COPD patients were included. At genus level, 68 different OTUs were found. No significant differences in the relative abundance of any of the detected genera were found between stability and exacerbation. Bacterial biodiversity, measured with Chao1 and Shannon indexes, showed no significant differences either. Beta-diversity analysis with Bray-Curtis index showed that the microbial composition was similar in both clinical situations (Adonis test R2= 0.02 p= 0.955). In the MG-RAST analysis, at KEGG level 2, 36 functional categories were found, 4 of them with significant differences.Cell growth and dead and Transport and catabolism decreased their abundance in exacerbation [1.6 (0.2-2) vs 4 (3-7) p=0.012 and 2 (0-3) vs 4 (2-5) p= 0.025] while Cancer and Carbohydrate metabolism were more abundant in exacerbation [0.8 (0-1.5) vs 0 (0-0.5) p= 0.043 and 7 (6-9) vs 6 (6.3-6.1) p= 0.012]. Conclusion: The microbiome composition did not show differences between stability and exacerbation samples. However, during an exacerbation, increases and decreases in some functional pathways are observed, suggesting that exacerbations are associated with an alteration in the functional activity of the bacterial community.