Asthma

Reduced gut microbiota diversity, i.e. an imbalance in gut microbiota composition (known as dysbiosis (sidenote: Dysbiosis Generally defined as an alteration in the composition and function of the microbiota caused by a combination of environmental and individual-specific factors. Levy M, Kolodziejczyk AA, Thaiss CA, et al. Dysbiosis and the immune system. Nat Rev Immunol. 2017;17(4):219-232.   ) ), in the first years of life is associated with an increased risk of developing asthma later in childhood.³ Some researchers believe that analyzing an infant’s gut microbiota could predict the risk of developing the disease.⁴ One factor behind such imbalances that has received much attention is the impact of antibiotics taken in the first weeks or months of life, i.e. when the gut microbiota and immunity are developing.⁵ Some studies have shown a link between antibiotic use and an increased risk of asthma later in childhood.⁶ Moreover, one research team has recently suggested that a gut dysbiosis in infants exposed to antibiotics may be responsible for childhood asthma.⁷ However, this mechanism has yet to be confirmed.

The lung microbiota is also thought to play a role, and although our understanding in this area is still very limited, it is a rapidly expanding field of research.⁸ The discovery of a unique lung flora with signatures specific to patients suggests a role in asthma.^9,10 Furthermore, it appears that respiratory function in moderate to severe asthma is associated with the degree of lung inflammation and the composition of the microbiota.^11,12 While research to confirm these results is ongoing, characterizing the bacterial populations living in the lower respiratory tract may help improve patient management or even better predict attacks.¹⁰

Data relating to the nasal microbiota are also very limited. However, an imbalance in the composition of the nasal microbiota has also been associated with the disease,¹³ and even with the severity of attacks,¹⁴ although no causal relationship has been established. Lastly, as with the gut microbiota, a very recent study on 700 children suggests that an alteration of the nasal microbiota due to antibiotic treatment before the age of 1 could explain the onset of childhood asthma at 7 years of age.¹⁵ However, this remains to be confirmed.

^{1 World Health Organization. 2021. Asthma. World Health Organization, Geneva, Switzerland. https://www.who.int/news-room/fact-sheets/detail/asthma}

^{2 Dharmage SC, Perret JL, Custovic A. Epidemiology of Asthma in Children and Adults. Front Pediatr. 2019 Jun 18;7:246.} 

^{3 Abrahamsson TR, Jakobsson HE, Andersson AF, et al. Low gut microbiota diversity in early infancy precedes asthma at school age. Clin Exp Allergy. 2014 Jun;44(6):842-50.} 

^{4 Stokholm J, Blaser MJ, Thorsen J, et al. Maturation of the gut microbiome and risk of asthma in childhood. Nat Commun. 2018 Jan 10;9(1):141.} 

^{5 Coker MO, Juliette C. Madan JC. Chapter 3 - The microbiome and immune system development, The Developing Microbiome. Academic Press. 2020. p 43-66.}

^{6 Murk W, Risnes KR, Bracken MB. Prenatal or early-life exposure to antibiotics and risk of childhood asthma: a systematic review. Pediatrics. 2011 Jun;127(6):1125-38.} 

^{7 Patrick DM, Sbihi H, Dai DLY, et al. Decreasing antibiotic use, the gut microbiota, and asthma incidence in children: evidence from population-based and prospective cohort studies. Lancet Respir Med. 2020 Nov;8(11):1094-1105.} 

^{8 Hauptmann M, Schaible UE. Linking microbiota and respiratory disease. FEBS Lett. 2016 Nov;590(21):3721-3738.}

^{9 Millares L, Bermudo G, Pérez-Brocal V, et al. The respiratory microbiome in bronchial mucosa and secretions from severe IgE-mediated asthma patients. BMC Microbiol. 2017 Jan 19;17(1):20.} 

^{10 Sullivan A, Hunt E, MacSharry J, et al. 'The Microbiome and the Pathophysiology of Asthma'. Respir Res. 2016 Dec 5;17(1):163.} 

^{11 Turturice BA, McGee HS, Oliver B, et al. Atopic asthmatic immune phenotypes associated with airway microbiota and airway obstruction. PLoS One. 2017 Oct 20;12(10):e0184566.}

^{12 Taylor SL, Leong LEX, Choo JM, et al. Inflammatory phenotypes in patients with severe asthma are associated with distinct airway microbiology. J Allergy Clin Immunol. 2018 Jan;141(1):94-103.e15.} 

^{13 Kang HM, Kang JH. Effects of nasopharyngeal microbiota in respiratory infections and allergies. Clin Exp Pediatr. 2021 Apr 15.}

^{14 Zhou Y, Jackson D, Bacharier LB, et al. The upper-airway microbiota and loss of asthma control among asthmatic children. Nat Commun. 2019 Dec 16;10(1):5714.}

^{15 Toivonen L, Schuez-Havupalo L, Karppinen S, et al. Antibiotic Treatments During Infancy, Changes in Nasal Microbiota, and Asthma Development: Population-based Cohort Study. Clin Infect Dis. 2021 May 4;72(9):1546-1554.} 

^{16 Meirlaen L, Levy EI, Vandenplas Y. Prevention and Management with Pro-, Pre and Synbiotics in Children with Asthma and Allergic Rhinitis: A Narrative Review. Nutrients. 2021 Mar 14;13(3):934.} 

^{17 Fonseca VMB, Milani TMS, Prado R, et al. Oral administration of Saccharomyces cerevisiae UFMG A-905 prevents allergic asthma in mice. Respirology. 2017 Jul;22(5):905-912.} 

^{18 Chiu CJ, Huang MT. Asthma in the Precision Medicine Era: Biologics and Probiotics. Int J Mol Sci. 2021 Apr 26;22(9):4528. doi: 10.3390/ijms22094528.}

^{19 O'Connor GT, Lynch SV, Bloomberg GR, et al. Early-life home environment and risk of asthma among inner-city children. J Allergy Clin Immunol. 2018 Apr;141(4):1468-1475.} 

^{20 Depner M, Taft DH, Kirjavainen PV, et al.  Maturation of the gut microbiome during the first year of life contributes to the protective farm effect on childhood asthma. Nat Med. 26(11):1766-1775. 2020 ;}

^{21 Mäki, J.M., Kirjavainen, P.V., Täubel, M. et al. Associations between dog keeping and indoor dust microbiota. Sci Rep. 2021 Mar 5;11(1):5341.}