Microbial contributions to bronchial asthma occurrence in children: A metagenomic study

Bronchial asthma, a common chronic respiratory disease in children, is traditionally regarded as a noninfectious disease. Current hypotheses, however, argue that asthma can be caused by microbial infection. We, therefore, hypothesize that a variety of microbes are more commonly found in the sputum of children with asthma, and these microbes may contribute to the occurrence and development of asthma. The present study proposes to use metagenomic approach to explore microbial diversity and to identify the microbial community characteristics of sputum from children with asthma. We found that microbial communities in the sputum of children differed significantly between asthmatics and controls. Kruskal-Wallis testing showed that 16 phyla, 104 genera, and 159 species were significantly downregulated, whereas two phyla including Platyhelminthes phylum and Chordata phylum, two genera including Spirometra genus and Homo sapiens, and the Spirometra erinaceieuropaei species were significantly upregulated in asthma patients compared with controls (P < 0.05). Among them, H. sapiens and S. erinaceieuropaei exhibited 2.3- and 2.0-fold overabundance in asthmatics vs controls, respectively. Meanwhile, metastats assay demonstrated that 31 phyla, 400 genera, and 813 species were significantly downregulated, whereas two phyla, 10 genera, and 16 species were significantly upregulated in asthma patients compared with controls (P < 0.05). Among them, Tetrahymena thermophila and Candidatus Zinderia insecticola exhibited 4.7-fold overabundance in asthmatics vs controls. Our study establishes a link between microbial infection and the mechanisms leading to asthma development, which will be useful for developing novel diagnostic biomarkers and aiding in the prevention and control of asthma.