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 genus Acinetobacter was more abundant in Estonian skin and nasal samples. Particularly, the strain‐level profile of Acinetobacter lwoffii was 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 genus Acinetobacter. 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 genus Acinetobacter in the allergy gap between the two populations. The significance of the observed differences for later allergic sensitization remains open. Estonian children had a more diverse intestinal microbiota than Finnish peers at the age of 6 months. Microbial community composition differed significantly between 6‐month‐old Estonian and Finnish children. Especially, genus Acinetobacter was more abundant in skin‐ and nasal samples of Estonian children. Our results support the importance of early exposure to environmental microbes and suggest that exposure to Acinetobacter might be particularly protective.Abbreviation: PCoA, principal coordinates analysis