Human milk has a microbiome that contains a wide variety of typical oral and skin bacteria, suggesting that the bacterial communities in the infant oral cavity and maternal skin contribute to the development of the human milk microbiome [1,2,3]. It is hypothesised that breastfeeding characteristics, such as feeding frequencies, total 24 h breastfeeding duration and breast pump use, could lead to different levels of exposure to oral and skin bacteria and subsequently altered bacterial profiles in human milk. In order to investigate the associations between breastfeeding characteristics and the human milk microbiome, this study analysed milk samples collected from 57 healthy lactating women at 3 months postpartum by full-length 16S rRNA gene sequencing. The results showed that breastfeeding characteristics were associated with neither Shannon diversity nor richness of the human milk microbiome. Total 24 h breastfeeding duration, however, was positively associated with Streptococcus salivarius (0.013 ± 0.006, p = 0.035). Mothers with normal milk production (≥600 mL/24 h) harboured less Streptococcus parasanguinis (−0.007 ± 0.003, p = 0.035) and Veillonella sp. (−0.008 ± 0.003, p = 0.011) in the milk. Breastfeeding frequency was positively associated with Pseudomonas sp. (0.204 ± 0.098, p = 0.042). In conclusion, total 24 h breastfeeding duration, breastfeeding frequency and 24 h milk production were associated with specific bacterial species in human milk.
Author Contributions
Conceptualization, L.F.S., M.P.N. and D.T.G.; methodology, L.F.S.; formal analysis, R.X. and L.F.S.; investigation, R.X. and A.S.C.; resources, D.T.G.; data curation, Z.G., S.L.P., J.L.M. and R.X.; writing—original draft preparation, R.X.; writing—review and editing, M.P.N., L.F.S., A.S.C., J.L.M., Z.G., S.L.P. and D.T.G.; visualization, R.X.; supervision, L.F.S., D.T.G. and M.P.N.; funding acquisition, D.T.G. All authors have read and agreed to the published version of the manuscript.
Funding
This research is funded by an unrestricted research grant from Medela AG (Switzerland).
Institutional Review Board Statement
The study was conducted in accordance with the Declaration of Helsinki and approved by the Human Research Ethics Committee of The University of Western Australia (RA/4/20/4023).
Informed Consent Statement
Informed consent was obtained from all subjects involved in the study.
Data Availability Statement
Sequence data have been submitted to the NCBI SRA (BioProject Submission: SUB13951443).
Acknowledgments
The authors would like to acknowledge Erika van den Dries for collecting the samples and Matthew Payne for the use of his laboratory space and equipment.
Conflicts of Interest
D.T.G. declares participation in the Scientific Advisory Board of Medela AG. D.T.G., J.L.M., Z.G. and L.F.S. receive a salary from an unrestricted research grant from Medela AG administered by The University of Western Australia. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results. M.P.N. and A.S.C. declare no conflicts of interest.
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