Lung Microbiome in Health and Disease

Luigina Romani ^1* Kurtis Francis Budden ²

• ¹ University of Perugia, Perugia, Perugia, Italy
• ² The University of Newcastle, Callaghan, New South Wales, Australia

In lung carcinogenesis, Zhai et al describes the interplay between bacteria and their metabolites in different early-stage lung cancer specimens that could be used as potential biomarkers to guide future therapeutic strategies (3). Different microbial richness was found in the different specimens, with a lower richness characterizing the early-stage adenocarcinoma. Bacterial species were also different in the different specimens, with Ralstonia associated with early lung adenocarcinoma, and Feacalibacterium and Blautia associated with ground glass nodules that had not progressed to solid nodules. Akkermansia, Escherichiashigella, and Klebsiella were instead associated with lung squamous carcinoma. Metabolites differed in the adenocarcinomas versus the squamous carcinoma, likely reflecting differing metabolic activities in energy and glutathione metabolism, respectively. Two articles focus on the influence of long-term inhaled corticosteroid and modulation of the respiratory microbiota in COPD. Yue et al. employed a single-center retrospective cohort study to compare alterations in airway function and the sputum microbial community structure between COPD patients who had undergone either long-term or short-term treatment with inhaled corticosteroid (4). The study found a significantly altered β-diversity of the microbial community structure in the sputum of patients on longtermcorticosteroids therapy, with an increased abundance of Abiotrophia, Schaalia, Granulicatella, Mogibacterium, Sphingobium, and Paraeggerthella bacterial genera compared to short-term corticosteroids. Some of these were positively correlated with the eosinophil %. Confirming the role of the oral microbiota in COPD clinical dynamics, Hua et al. found that oral probiotic Lactobacillus rhamnosus GG administration significantly delayed exacerbation in patients with moderate-to-very severe COPD, an effect similarly obtained upon influenza-S. pneumoniae vaccination (5). Finally, Garaci et al. discuss the intricate inter-microbe association networks that comprise true mutualistic or antagonistic direct or indirect relationships in the respiratory tract (6). In particular, the analysis of the tripartite interaction of bacteria, fungi and the mammalian host has highlighted how the understanding of the metabolic and immune significance of their interaction could be valuable in development of novel druggable targets in disease treatments.Overall, the articles included in this Research Topic highlight important aspects associated with the microbiota dynamics in the respiratory tract that help paving the way for the development of microbial based therapeutics approaches.