Lower Airway Microbiota

Abstract

During the last several years, the interest in the role of microbiota in human health has grown significantly. For many years, the lung was considered a sterile environment, and only recently, with the use of more sophisticated techniques, has it been demonstrated that colonization by a complex population of microorganisms in lower airways also occurs in healthy subjects; a predominance of some species of Proteobacteria, Firmicutes, and Bacteroidetes phyla and with a peculiar composition in some disease conditions, such as asthma, have been noted. Lung microbiota derives mainly from the higher airways microbiota. Although we have some information about the role of gut microbiota in modulation of immune system, less it is known about the connection between lung microbiota and local and systemic immunity. There is a correlation between altered microbiota composition and some diseases or chronic states; however, despite this correlation, it has not been clearly demonstrated whether the lung microbiota dysbiosis could be a consequence or a cause of these diseases. We are far from a scientific approach to the therapeutic use of probiotics in airway diseases, but we are only at the starting point of a knowledge process in this fascinating field that could reveal important surprises, and randomized prospective studies in future could reveal more about the clinical possibilities for controlling lung microbiota. This review was aimed at updating the current knowledge in the field of airway microbiota.

Dysbiosis of the gut and lung microbiome has a role in asthma

“…The microbiome of the upper respiratory tract is accessible even in infants and has been investigated in many studies in the context of asthma development or already established asthma phenotypes in children, in particular, as the upper airway microbiota seems to be the main contributor to the lower airway composition [29]. In this respect, nasal secretion samples from asthmatic children from 6 to 17 years of age showed a distinct microbiota composition dominated by genus Moraxella which was associated with increased exacerbation risk and activation of eosinophils [30].…”

The Human Respiratory System and its Microbiome at a Glimpse

“…Bacterial phylum composition, in order of population number, is as follows: Bacteroidetes, Firmicutes, Proteobacteria, Fusobacteria, and Actinobacteria. At the gender level, there are Veillonella, Prevotella, Fusobacteria, Streptococcus and others (less presence of potential pathogens such as Haemophilus ) ( Table 1 ) [ 1 , 24 , 25 ].…”

“…The lungs do not have a similar microbiome in all tracts (bronchi, bronchioles, alveoli) and, therefore, the pulmonary composition depends on a multitude of factors, in particular: (a) microbial immigration (micro-aspiration, inhalation of microorganisms, direct mucous dispersion), (b) microbial elimination (cough, muco-ciliary clearance, innate and adaptive immunity) and (c) local growth conditions (nutritional availability, temperature, partial O 2 tension, local microbial competition, concentration and activity of inflammatory cells). The reduction in the microbial elimination capacity both increases regional growth conditions and creates dysbiosis, and therefore leads to a high risk of lung disease [ 24 , 26 , 27 ].…”

Bacteriotherapy with Streptococcus salivarius 24SMB and Streptococcus oralis 89a nasal spray for treatment of upper respiratory tract infections in children: a pilot study on short-term efficacy

“…Recently, to prevent RRIs and avoid inappropriate therapy as well as to reduce the incidence of drug resistance, alternative treatments have been proposed [12]. An interesting way has been highlighted by the study of nasal microbiome that, interacting with the local epithelial and immune cells, evoking systemic immune responses and, eliminating the invading species, acts as a "health friendly bacteria" [13,14]. In light of these beneficial properties, authors successfully looked to the vital bacteria, better known as probiotics, for reinforcement of microbiome homeostasis as an additional and effective weapon against RRIs [15][16][17].…”