In this work, variation in microbiota in the lower respiratory tract (LRT) among asthmatic and non-asthmatic subjects is identified. All participants (27 asthmatic patients and 27 non-asthmatic subjects) were asked to expectorate a sputum sample in special sterile tubes after rinsing the mouth with a sterilizing solution. The expectorated sputum specimen was immediately homogenized and stored in the deep freezer for DNA extraction for microbial gene sequencing and sequence analyses. For sequencing the V4 region of the 16S rRNA gene was sequenced using Illumina MiSeq, followed by an analysis of alpha and beta diversity. It was found that asthmatic patients had greater bacterial diversity than non-asthmatic subjects. Bacteria associated to the phyla (Bacteroidetes, Proteobacteria, and Firmicutes) accounted for 90 % of all sequences. The relative abundance of Proteobacteria in the asthmatic patients was higher than that of non-asthmatic (30 % vs 17 %; P-value = 0.044), along with a high abundance of the pathogen Haemophilus influenza. In contrast, Firmicutes (41 %) and Bacteroidetes (31 %) showed higher relative abundances in the non-asthmatic subjects. No significant link was found between the type of asthma drug or the method of drug usage (orally or via inhalation) and the respiratory microbiota. Therefore, the variations in LRS microbiota are not caused by the drugs taken by the asthmatic patients, rather they might be connected to the etiology of asthma. Since the asthmatic patients had higher proportions of Haemophilus influenzae, these organisms could be a causative factor in the pathophysiology of asthma.
Keywords: Asthma; Haemophilus influenzae; Inhalers; Oral corticosteroids; Respiratory microbiota.
© 2022 The Author(s).