A metagenomic approach through t-RFLP to the microbiome of asthma

Background: Recent metagenomic approaches succeeded in characterizing the microbial communities of airway diseases present in bronchoalveolar lavage and supernatants of induced sputum but those results were limited by small sample size and lack of microbial information from inflammatory cells and epithelial cells of airways. We investigated the use of terminal restriction fragment length polymorphism (T-RFLP) analysis, in conjunction with multivariate statistical methods, to examine the difference of micro biota in whole induced sputum (inflammatory cells and epithelial cells in addition to supernatant) between normal control and asthma.

Methods: Induced sputum samples were obtained from 36 normal nonsmoker subjects and 89 patients with steroid naïve asthma. Through T-RFLP analysis, operational taxonomic units (OTUs), representing bacterial species or taxonomically related groups, and relative amounts of each OTUs were evaluated.

Results: The global R value for differences between normal control and asthma was 0.148 (P=0.002). Dissimilarities in bacterial communities of induced sputum between normal control and asthma was 28.74%. OTUs contributing to normal control-asthma differences were identified. OTU 789 (Lachnospiraceae, 3.1 fold), 517 (Comamonadaceae, Acetobacteraceae, Chloroplast, 1.9 fold), 633 (Prevotella, 1.9 fold), 645 (Actinobacteria, Propionibacterium acnes, 1.8 fold), 607 (Lactobacillus buchneri, Lactobacillus otakiensis, Lactobacillus sunkii, Rhodobacteraceae, 1.8 fold), 661 (Acinetobacter, Pseudomonas, Leptotrichiaceae, 1.8 fold), 650 (Brevibacteriaceae, Lachnospiraceae, Fusobacterium, 1.5 fold), 821 (Lachnospiraceae, Acinetobacter, Actinomyces, 1.5 fold), 415 (Comamonadaceae, Streptomycetaceae, 1.5 fold) were significantly more prevalent in the sputum of asthma patients than normal control.

Conclusion: Patients with asthma have an altered microbial composition in the respiratory tract.