Lung microbiome and origins of the respiratory diseases

• Published in: Current research in immunology 2023-01, Vol.4, p.100065-100065, Article 100065
• Main Authors: Belizário, José, Garay-Malpartida, Miguel, Faintuch, Joel
• Format: Article
• Language: English
• Subjects: ARDS; Community-acquired pneumonia; COPD; from the special issue: Role of host-microbiome interactions during pneumonia, edited by Antoine Roquilly and Karim Asehnoune; Inflammation; Microbiomes; Respiratory diseases
• ISSN: 2590-2555; 2590-2555
• DOI: 10.1016/j.crimmu.2023.100065

The studies on the composition of the human microbiomes in healthy individuals, its variability in the course of inflammation, infection, antibiotic therapy, diets and different pathological conditions have revealed their intra and inter-kingdom relationships. The lung microbiome comprises of major species members of the phylum Bacteroidetes, Firmicutes, Actinobacteria, Fusobacteria and Proteobacteria, which are distributed in ecological niches along nasal cavity, nasopharynx, oropharynx, trachea and in the lungs. Commensal and pathogenic species are maintained in equilibrium as they have strong relationships. Bacterial overgrowth after dysbiosis and/or imbalanced of CD4+ helper T cells, CD8+ cytotoxic T cells and regulatory T cells (Treg) populations can promote lung inflammatory reactions and distress, and consequently acute and chronic respiratory diseases. This review is aimed to summarize the latest advances in resident lung microbiome and its participation in most common pulmonary infections and pneumonia, community-acquired pneumonia (CAP), ventilator-associated pneumonia (VAP), immunodeficiency associated pneumonia, SARS-CoV-2-associated pneumonia, acute respiratory distress syndrome (ARDS) and chronic obstructive pulmonary disease (COPD). We briefly describe physiological and immunological mechanisms that selectively create advantages or disadvantages for relative growth of pathogenic bacterial species in the respiratory tract. At the end, we propose some directions and analytical methods that may facilitate the identification of key genera and species of resident and transient microbes involved in the respiratory diseases’ initiation and progression. [Display omitted] •Which is the most reliable method(s) to assess respiratory tract microbiome: oral swabs, pharyngeal secretions, sputum, endotracheal aspirate (ETA), bronchoalveolar lavage fluid (BAL), microlavage (mBAL), bronchoscopy aspiration, plasma samples?•How does one define the normal respiratory tract microbiome, with quantitative and qualitative cut-off points for dysbiosis? Is the approach defended by some investigators acceptable, in the sense that dysbiosis coincides with low alpha and beta diversity and less abundance of “protective” oral-origin commensal bacteria? Which limits should be considered?•Specifically for pneumonia (community acquired, nosocomial and other variants), pathogen cut-off points are essential, as standard microbiome sequencing might elicit many potential agents