The human milk microbiome aligns with lactation stage and not birth mode

Abstract

We analysed the human milk microbiome in a cohort of 80 lactating women and followed the dynamics in taxa over the course of lactation from birth to 6 months. Two hundred and thirty one milk samples were collected from full-term lactating women at 1, 4, 8 and 24 weeks following birth and analysed for microbiota composition using 16S rRNA sequencing. A significant decrease in milk microbiota diversity was observed throughout the first 6 months of lactation, with the greatest difference seen between week 8 and week 24. Nine genera predominated in milk over lactation from week 1 to week 24, comprising of Staphylococcus, Streptococcus, Pseudomonas, Acinetobacter, Bifidobacterium, Mesorhizobium, Brevundimonas, Flavobacterium, and Rhodococcus; however, fluctuations in these core genera were apparent over time. There was a significant effect of stage of lactation on the microbiome, while no effect of birth mode, infant sex and maternal BMI was observed throughout lactation. Streptococcus had the highest mean relative abundance at week 1 and 24 (17.3% and 24% respectively), whereas Pseudomonas predominated at week 4 (22%) and week 8 (19%). Bifidobacterium and Lactobacillus had the highest mean relative abundance at week 4 (5% and 1.4% respectively), and occurred at a relative abundance of ≤ 1% at all other time points. A decrease in milk microbiota diversity throughout lactation was also observed. This study concluded that lactation stage was the primary driving factor in milk microbiota compositional changes over lactation from birth to 6 months, while mode of delivery was not a factor driving compositional changes throughout human lactation.

A Pilot Study on Donor Human Milk Microbiota: A Comparison with Preterm Human Milk Microbiota and the Effect of Pasteurization

“…On the other hand, our finding on alpha diversity is in contrast with previous reports, showing similar values between DHM and PT-MOM samples [34,41]. It must be said that the lactation stage has also been shown to have an impact on the HM microbiota [42]. Regarding mother-term infant dyads, several factors including mode of breastfeeding, lactation stage, and maternal body mass index, have been associated with the overall composition of the milk microbiota, although the cumulative association of all the factors assessed in a multivariate analysis explained approximately 25% of the total variation in the milk microbiota composition [32].…”

Dynamic Changes in the Human Milk Metabolome Over 25 Weeks of Lactation

“…Moreover, we comprehensively characterize HM composition from macronutrient level to metabolite level, including fatty acid profiles in HM of mothers delivering term over 6 months of lactation. Furthermore, we have also recently reported on the HM microbiome in this cohort of lactating women over the course of lactation from birth to 6 months (75).…”

The Manifold Bioactivity and Immunoreactivity of Microbial Proteins of Cow and Human Mature Milk in Late Lactation

“…That is why cow’s milk proteins, as the first cross-species protein source, are considered the main food-borne foreign antigens affecting an infant’s immune system. Among the most important components of both human and other types of mammalian milk are microorganisms [ 10 , 19 , 22 , 40 ]. The proteins of the microorganisms present in milk have not yet been sufficiently tested with respect to their immunoreactivity.…”

“…In particular, the role of the dynamically changing composition of the HM microbiota during the breastfeeding period is an issue that requires further research in terms of its pro-health potential [ 10 ]. There is a high microbial variability in the milk material between individuals, resulting from many factors such as diet and stress, among others [ 11 ].…”