Intestinal microbiota and the “allergic phenotype” in children

Abstract

Objective. To evaluate the composition of intestinal microbiota in children with atopic dermatitis (AD) aged 1–5 years depending on the disease severity. Patients and methods. We have examined 60 children aged between 1 and 5 years diagnosed with AD. In outpatient settings, they have undergone comprehensive clinical and laboratory examination that included analysis of patient's medical history, physical examination, assessment of clinical status using the SCORAD scale, complete blood count, urinalysis, analysis of feces, liver function tests, measurement of total IgE and specific IgE, and bacteriological analysis of feces. The composition of intestinal microbiota was assessed using bacterial 16S rRNA gene sequencing with subsequent bioinformatic and statistical analysis. Results. The analysis of intestinal microbiota in 60 AD children aged 1–5 years using 16S rRNA sequencing demonstrated an association between the composition of intestinal microflora and disease severity. Both bacterial count and species diversity directly depend on the disease course. Children with complicated AD had a very poor diversity of intestinal microorganisms compared to those in remission (р ≤ 0.002). Children with signs of AD exacerbation demonstrated an increased count of Actinobacteria species (р = 0.018) and a decreased count of Proteobacteria species compared to children without clinical manifestations of AD (р = 0.033). We also observed a decrease in the amount of bacteria belonging to Oscillospiraceae and Erysipelatoclostridiaceae families (р = 0.03 : 0.034) in children with AD exacerbation and children with signs of secondary infection. Patients with acute disease and patients with signs of secondary infection were also more likely to have lower level of Bifidobacterium longum (р = 0.03 : 0.034) than patients in remission. Conclusion. Our findings suggest that the intestinal microbiota of children in remission differs from that in children with AD exacerbation or complicated AD. The composition of commensal flora, as well as species richness directly depend on the disease severity. Children with AD exacerbation were found to have lower concentration of Oscillospiraceae species and B. longum that are crucial for normal functioning of the gastrointestinal tract and modulation of the immune response. Understanding of the metabolic potential of bacteria will enable adequate diet correction of the intestinal microbiota. Thus, sequencing of bacterial 16S rRNA genes is very helpful in the diagnosis of AD. It also opens new horizons in the search for new treatment methods. Key words: alpha diversity, atopic dermatitis, children, intestinal microbiota, molecular genetic methods, 16S sequencing