Analysis of the bronchoalveolar lavage fluid microbial flora in COPD patients at different lung function during acute exacerbation

There is a correlation between the dysbiosis of the respiratory microbiota and the occurrence, severity, frequency, and mortality of Chronic Obstructive Pulmonary Disease (COPD). However, it is not unclear if there are differences in the bronchoalveolar lavage fluid (BALF) microbiota among patients at differente lung function. In this study, BALF samples were collected from 70 COPD patients experiencing acute exacerbations (AECOPD). The patients were divided into a mild group (FEV1/pre ≥ 50; PFT I, n = 50) and a severe group (FEV1/pre < 50; PFT II, n = 20) according to the lung function: or a frequent exacerbation (FE, n = 41) group and a non-frequent exacerbation (NFE, n = 29) group according to their exacerbation history. Microbiota analysis of BALF samples was conducted using mNGS and bioinfromatic analysis. Compared to PFT I group, PFT II group exhibited a significant decrease in species diversity (Shannon index), as well as a significant reduction in total species count and richness (Chao1, ACE indices). NFE group demonstrated diversity similar to that of FE group. Conversely, the microbial diversity of NFE group was comparable to that of FE group. The most abundant bacterial genera were Streptococcus, Prevotella, Veillonella, Rod-shaped Bacillus, and Rothia. Aspergillus was the most dominant fungal genus in AECOPD. Lymphocryptovirus was the most prevalent virus in AECOPD.Compared to the PFT I group, Corynebacterium's abundance significantly increased in PFT II group. Furthermore, FE group showed a notable increase in Streptococcus mitis abundance relative to NFE group. Bubble plot analysis revealed a significant increase in Moraxella, Fusobacterium, Haemophilus, Pseudomonas, Streptomyces, and Klebsiella in PFT II group, including a notable increase in typical Veillonella, Actinomyces, and Gordonia. The NFE group exhibited a significant increase in Bacteroides and Prevotella's relative abundance. Spearman correlation analysis revealed strong positive correlations among certain microbial communities. There exists a significant variation in microbial composition across groups of AECOPD patients at different lung function. Specifically, patients with severe airflow limitations exhibit a significant reduction in microbial diversity. Additionally, distinct bacterial taxa are enriched in patients characterized by varying levels of airflow limitation and exacerbation frequency. These observations offer vital insights into the pathogenesis of AECOPD, suggesting a potentially crucial role for the microbiota in its development. Such findings pave the way for identifying potential therapeutic targets and intervention strategies, ultimately aiming to improve treatment outcomes for AECOPD patients.