Transmission of gut sIgA coated bacteria from mother to infant through breast milk

Vertical transmission of bacteria from breast milk of a mother to infant is an important source of microbial colonization in offspring. sIgA receptors on the surface of gut Peyer’s patches are involved in bacterial translocation. This study aims to prove that sIgA-coated may migrate to breast milk and transmits to infant gut. Fecal and breast milk samples were collected from multiple mother-infant pairs during the first year of life. We separated bacterial fractions coated with secretory immunoglobulin A (sIgA) by magnetic activated cell sorting (MACS). Microbiome were analyzed by 16s ribosomal RNA (rRNA) gene amplicons. Microbiome of breast milk, neonatal and maternal feces showed unique microbial profile that was dominant by Streptococcus, Bifidobacterium and Faecalibacterium, respectively. Microbiome of these samples was lactation-specific. Composition sIgA coated bacteria from mother's feces, breast milk and infant's feces were most similar in the mature milk stage. and body mass index（BMI） before pregnancy and after delivery showed different correlation with bacteria in breastmilk and maternal. We identified cooccurrence of eight genera among sIgA coated gut microbiota of mother, breast milk and infant gut including Streptococcus, Staphylococcus, Lactobacillus (s_Lactobacillus gasseri), Enterococcus, Bifidobacterium (s_Bifidobacterium_longum_subsp_longum), Klebsiella, Ambigous and Escherichia-Shigelle. These bacteria may achieve vertical transmission through sIgA receptors. Our findings reveal novel mother-neonate microbial vertical transmission events at high perspective and give insights into early acquisition of the infant gut.