From the press release:
“'We found that milk bacteria are different in mothers who pump their milk,'” said Dr. Meghan Azad, the University of Manitoba investigator who led the study. “'We suspect that pumping may prevent the transfer of oral bacteria from the infant to the mother and might introduce other bacteria from the pump. Therefore, contrary or in addition to the hypothesis that milk bacteria come from the mother’s gut, our results suggest that the infant’s oral bacteria are important in shaping the milk microbiota.'"
Title: Composition and Variation of the Human Milk Microbiota Are Influenced by Maternal and Early-Life Factors.
Authors: Moossavi S, Sepehri S, Robertson B, Bode L, Goruk S, Field CJ, Lix LM, de Souza RJ, Becker AB, Mandhane PJ, Turvey SE, Subbarao P, Moraes TJ, Lefebvre DL, Sears MR, Khafipour E, Azad MB.
In: Cell Host & Microbe 2019 Feb 13;25(2):324-335.e4. doi: 10.1016/j.chom.2019.01.011.
Summary: "Breastmilk contains a complex community of bacteria that may help seed the infant gut microbiota. The composition and determinants of milk microbiota are poorly understood. Among 393 mother-infant dyads from the CHILD cohort, we found that milk microbiota at 3-4 months postpartum was dominated by inversely correlated Proteobacteria and Firmicutes, and exhibited discrete compositional patterns. Milk microbiota composition and diversity were associated with maternal factors (BMI, parity, and mode of delivery), breastfeeding practices, and other milk components in a sex-specific manner. Causal modeling identified mode of breastfeeding as a key determinant of milk microbiota composition. Specifically, providing pumped breastmilk was consistently associated with multiple microbiota parameters including enrichment of potential pathogens and depletion of bifidobacteria. Further, these data support the retrograde inoculation hypothesis, whereby the infant oral cavity impacts the milk microbiota. Collectively, these results identify features and determinants of human milk microbiota composition, with potential implications for infant health and development.”