Chronic Obstructive Pulmonary Disease (COPD) is a disease of public health concern globally. It is the third leading cause of death worldwide, and the second leading cause in India. Tobacco and biomass smoke are the main causes leading to different lung diseases. Chronic exposures to tobacco smoke and biomass smoke have been shown to be associated with the risk of developing COPD. In India, there is high prevalence of COPD due to biomass smoke and tobacco smoke exposure. Microbial diversity in tobacco-smoke associated COPD has been studied earlier, microbiota in biomass smoke associated COPD was not yet explored.
A collaborative study was conducted by researchers at KEM hospital Pune, NCMR Pune and Chest Research foundation Pune to understand the biomass and tobacco smoke associated microbiota in COPD. It was not well studied whether there is a difference in the microbiota between healthy subjects and biomass smoke-associated COPD (BMSCOPD) subjects and between BMSCOPD and tobacco smoke-associated COPD (TSCOPD) subjects. The aim of the study was to compare nasal and oral microbiota between healthy, TSCOPD and BMSCOPD from rural population in India. This study suggests that disruption or imbalance in microbial community happens which may further contribute to the progression of COPD.
Study subjects were recruited from the population of KEM Hospital research centre, Vadu, HDSS . Subjects who were diagnosed with COPD were randomly selected from the cohort of COPD subjects. Nasal swabs and oral washings were collected from all the 31 subjects. Amplicon sequencing of bacterial 16S rRNA gene, bioinformatics and statistical analysis was done.
Results indicated that microbial communities differed significantly between nasal and oral samples. Greater diversity and higher interindividual variations were observed in nasal samples as compared to oral samples. The findings also indicated that, not all but few specific taxa contribute to the alteration in microbial community structure from healthy to disease state.
To compare the microbial diversity between healthy and disease state, all the COPD samples (TSCOPD and BMSCOPD) were pooled together and compared with healthy subjects. In the nasal samples, researchers found significant increase in the abundance of Actinomyces, Actinobacillus, Megasphaera, and Selenomonas in COPD group, whereas Propionibacterium was significantly higher in the healthy subjects. In the oral samples, they noted a significant increase in the abundance of Corynebacterium, Selenomonas, and Actinomyces among COPD subjects compared to healthy subjects. In the nasal samples, they found a significantly higher abundance of the phyla Planctomycetes and Armatimonadetes in TSCOPD as compared to BMSCOPD, while Acidobacteria were significantly abundant in BMSCOPD as compared to TSCOPD in the oral samples. Between healthy and BMSCOPD, in nasal samples, they found that 15 genera were significantly different in their abundance between the healthy and BMSCOPD. In oral samples, they found 14 genera which were significantly diferent in their abundance between the healthy and BMSCOPD. A significant difference was found for Haemophilus in oral samples.
It is the first study that has examined differences in the nasal and oral microbiota between healthy, TSCOPD, and BMSCOPD subjects in an Indian rural population. Although there were no significant differences in the overall microbial community structure, they reported significant differences in the microbiota in some key taxa between healthy and COPD subjects and also between TSCOPD and BMSCOPD subjects. Between healthy and COPD subjects, they reported a significant increase in the abundance of Actinomyces, Actinobacillus, Megasphaera, and Selenomonas in the nasal samples of COPD subjects, while Corynebacterium, Selenomonas, and Actinomyces were found to be increased in the oral samples of COPD subjects. Between TSCOPD and BMSCOPD subjects, they reported that Gallibacterium and Methanosaeta were significantly higher in the nasal samples of BMSCOPD subjects, while Acinetobacter was significantly higher in the oral samples of TSCOPD subjects.
The difference in the bacterial communities in BMSCOPD and TSCOPD suggests difference in pathophysiology of the disease and also suggests clinical phenotypic differences between these two groups. Thus, the pathophysiology of TSCOPD and BMSCOPD may differ due to the differences in microbial communities and, this should be considered carefully before designing the treatment method for COPD.