Contrasting Microbiotas Between Finnish And Estonian Infants: Exposure To Acinetobacter May Contribute To The Allergy Gap

Background Allergic diseases are more common in Finland than in Estonia, which-according to the biodiversity hypothesis-could relate to differences in early microbial exposures. Methods We aimed at defining possible microbial perturbations preceding early atopic sensitization. Stool, nasal and skin samples of 6-month-old DIABIMMUNE study participants with HLA susceptibility to type 1 diabetes were collected. We compared microbiotas of sensitized (determined by specific IgE results at 18 months of age) and unsensitized Estonian and Finnish children. Results Sensitization was differentially targeted between populations, as egg-specific and birch pollen-specific IgE was more common in Finland. Microbial diversity and community composition also differed; the genusAcinetobacterwas more abundant in Estonian skin and nasal samples. Particularly, the strain-level profile ofAcinetobacter lwoffiiwas more diverse in Estonian samples. Early microbiota was not generally associated with later sensitization. Microbial composition tended to differ between children with or without IgE-related sensitization, but only in Finland. While land-use pattern (ie green areas vs. urban landscapes around the children's homes) was not associated with microbiota as a whole, it associated with the composition of the genusAcinetobacter. Breastfeeding affected gut microbial composition and seemed to protect from sensitization. Conclusions In accordance with the biodiversity hypothesis, our results support disparate early exposure to environmental microbes between Finnish and Estonian children and suggest a significant role of the genusAcinetobacterin the allergy gap between the two populations. The significance of the observed differences for later allergic sensitization remains open.