Breastmilk microbiota of mothers whose children did or did not develop allergic manifestations.

Allergic diseases have become a major public health problem in affluent societies. Early colonization with a diverse microbiota seems to play a crucial role for appropriate immune maturation during childhood, and breastmilk microbiota is one important source of microbes for the infant, transferred together with maternal IgA antibodies. We previously observed that allergy development during childhood was associated with aberrant IgA responses to the gut microbiota already at 1 month of age, when the IgA antibodies are predominantly maternally derived. In this study, by using a combination of flow cytometric cell sorting and Illumina 16S rRNA sequencing, we sought to determine the microbial composition and IgA coating patterns of bacteria in breastmilk collected at 1 month post partum from 40 mothers whose children did or did not develop allergic and asthmatic symptoms during the first 7 years of life. The milk fed to children developing allergic manifestations had significantly lower bacterial richness when compared to the milk given to children that remained healthy. The proportions of IgA bound bacteria and the total bacterial load were similar in breastmilk between mothers of healthy children and those developing allergies, however the bacterial patterns of IgA coating appeared distinctive. In conclusion, consumption of breastmilk with a reduced microbial richness and divergent IgA bacterial recognition pattern in the first month of life may increase the risk for allergy development.