Contributions to human breast milk microbiome and enteromammary transfer of Bifidobacterium breve

Abstract

2021 Increasing evidence supports the importance of the breast milk microbiome in seeding the infant 22 gut. However, the origin of bacteria in milk and the process of milk microbe-mediated seeding of 23 infant intestine need further elucidation. Presumed sources of bacteria in milk include locations 24 of mother-infant and mother-environment interactions. We investigate the role of mother-infant 25 interaction on breast milk microbes. Shotgun metagenomics and 16S rRNA gene sequencing 26 identified milk microbes of mother-infant pairs in breastfed infants and in infants that have never 27 latched. Although breast milk has low overall biomass, milk microbes play an important role in 28 seeding the infant gut. Breast milk bacteria were largely comprised of Staphylococcus, 29 Streptococcus, Acinetobacter, and Enterobacter primarily derived from maternal areolar skin and 30 infant oral sites in breastfeeding pairs. This suggests that the process of breastfeeding is a 31 potentially important mechanism for propagation of breast milk microbes through retrograde flux 32 via infant oral and areolar skin contact. In one infant delivered via Caesarian section, a distinct 33 strain of Bifidobacteria breve was identified in maternal rectum, breast milk and the infant's 34 stool potentially suggesting direct transmission. This may support the existence of microbial 35 translocation of this anaerobic bacteria via the enteromammary pathway in humans, where 36 maternal bacteria translocate across the maternal gut and are transferred to the mammary glands.

Antibiotics and the developing intestinal microbiome, metabolome and inflammatory environment in a randomized trial of preterm infants

“…Exclusive or partial feeding with mother's own milk appeared to have higher bacterial load compared to formula and NPO, though not significantly. This observation is backed by previous evidence that breast milk harbors maternal-originating bacteria, as well as nutritional components (prebiotics) that support bacterial proliferation in the intestinal tract 40,41 . Interestingly, formula-fed infants had comparable levels of richness and diversity as mother's milk.…”

Effect of a reduced fat and sugar maternal dietary intervention during lactation on the infant gut microbiome

“…The most likely mechanisms by which maternal diet affects the infant gut microbiome and for which the most robust evidence exists is the entero-mammary pathway (Jiménez et al, 2008;Jost et al, 2014;Rodríguez, 2014;Milani et al, 2015;Fernández et al, 2016;Asnicar et al, 2017;Duranti et al, 2017;Murphy et al, 2017;Kordy et al, 2020), wherein gut bacteria are transported to the lactating mammary gland and thereby contribute to the human milk (HM) microbiome. It is well established that diet is a key factor that shapes the gut microbiome (De Filippo et al, 2010;Wu et al, 2011;Fava et al, 2012;Yatsunenko et al, 2012;Lin et al, 2013;David et al, 2014;Graf et al, 2015;Kovatcheva-Datchary et al, 2015;De Filippis et al, 2016;Mandal et al, 2016;Röytiö et al, 2017).…”

A Scoping Review of Research on the Human Milk Microbiome

“…Human milk has three sources of microbes that may influence the HMM. The milk produced by the glands in the breast, the skin around the areola, and the infant's mouth all contribute microbes into the milk (Kordy et al, 2020). In addition, collection of the milk may introduce environmental contaminants.…”