The role of fungal microbiota in asthma

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The link between dysbiosis and childhood asthma is created in the early months of life. A study conducted in rural Ecuador paves the way for new means to prevent the disease by stimulating protective bacteria and fungi.

 

In 2016, an international team that studied Canadian children discovered that asthma takes shape in the first months of life, and that the intestinal microbiota is the main predictive factor.  In a new study, that same team investigated whether the phenomenon also occurs in developing countries. They focused on a rural area in Ecuador, where prevalence of asthma also rounds 10% and where  conditions are favorable to developing a microbiota very different from that observed in developed countries.

Dysbiosis in wheezing children

During a period of three years, the researchers extracted stool samples of 2404 newborns at 3 months of age.  Five years later, they formed two groups, one including 27 children with atopic wheeze and a control group composed by 70 healthy children, and analyzed their fecal microbiota. Although it was different from the original Canadian study, this study revealed that children with asthma in Ecuador also have a dysbiosis, characterized by overabundance of the genera Streptococcus and Bacteroides and a lower proportion of Bifidobacterium. This confirmed that a microbial signature associated with the later development of asthma is present in the few months of life.

Common microbial metabolism

Since short chain fatty acids (SCFA) can stimulate regulatory T cells which are able to mitigate the allergic inflammatory response, their concentrations were measured (including butyrate, propionate and acetate). The objective was to associate microbial dysbiosis with metabolic changes in the microbiota. Wheezing children included in the two studies had a lower concentration of acetate in their stool, thus suggesting that children with asthma share the same microbial metabolism. In other words, a lower acetate concentration in a baby’s microbiota could increase their risk of developing asthma later in life.

Mycobiota and immune regulation

The analysis of the fungal microbiota produced even more surprising results: the researchers focused on this aspect because previous non-clinical studies had shown that, in the first three months of life, fungal community is a lot more diverse than later in life and that it plays a role in immune regulation (in mice, antibiotic-induced dysbiosis generates a proliferation of Candida albicans which is responsible for bronchial inflammation). In the study conducted in Ecuador, fungal dysbiosis was more pronounced than the bacterial one and the yeast Pichia kudrazvezii was very abundant in children with asthma. These results support the need to carry out further research into these still unknown components of the intestinal microbiota and provide a promising lead to prevent asthma in the first months of life by correcting the disrupted microbiota (including fungi).

 

Sources:

MC Arrieta et al. Associations between infant fungal and bacterial dysbiosis and childhood atopic wheeze in a nonindustrialized setting. J Allergy Clin Immuno 2017 Nov 30. pii: S0091-6749(17)31649-4