The pulmonary microbiota
It was long believed that healthy lungs contained no microorganisms. That’s been called into question since the recent discovery of the pulmonary microbiota.
The composition of the pulmonary microbiota is shaped primarily by environment: climate, geographic zone, the area where you live, and exposure to domestic animals, among others, but it also has many similarities with the intestinal microbiota. The flora in the lower respiratory tract (lungs, bronchi, etc.) is nowhere near uniform, and varies significantly from that of the upper respiratory tract (nose, mouth). Its role is poorly understood, but it might protect us from allergy- related inflammation.
Multiple factors can weaken bacterial diversity and lead to imbalance in the respiratory microbiota: some are related to the body (lowered immune defenses, problems with coughing, etc.), others are environmental (tobacco, viral infections, antibiotic treatment, etc.). Imbalance (dysbiosis) in the pulmonary microbiota may promote the emergence of pathogenic bacteria or fungi, and contribute to the development of chronic respiratory diseases, such as asthma or chronic obstructive pulmonary disease (COPD).
Michon A-L, Marchandin H. Diversité physiopathologique du microbiote respiratoire. Revue Francophone des Laboratoires - février 2015 - n°469.
Shukla SD, Budden KF, Neal R, et al. Microbiome effects on immunity, health and disease in the lung. Clin Transl Immunology. 2017;6(3):e133. Published 2017 Mar 10.