The gut microbiome co-develops with the immune system in infants and plays an important role in maintaining host homeostasis. The mechanisms of initial acquisition and development of the microbiome are poorly understood. Breast milk contains a diverse population of bacteria, but very little is known about the vertical transfer of microbes from mother to infant by breastfeeding.
Breast milk, areolar skin swab, and infant stool samples were prospectively and longitudinally collected from 107 healthy mother-infant pairs. The bacterial component was characterized by 16S sequencing using Illumina MiSeq. We compared diversity, composition, and functional differences by demographic and infant feeding characteristics using QIIME, SourceTracker, PICRUSt and STAMP.
Median infant age at time of specimen collection was 40 days (range 1-800 days). Distinct microbial communities comprised dominant taxa of Proteobacteria in milk, Firmicutes in areolar swabs, and Proteobacteria and Actinobacteria in stool. The infant stool microbial community was more closely related to their own mother's milk and skin compared to a random mother (Bray-Curtis, p<0.001). During the first 30 days of life, exclusively breastfed infants received 35.0 ± 18.9% microbes from breast milk and 11.8 ± 7.1% from areolar skin. Contribution of microbes from mother's milk and skin decreased as the infant aged, but the mother's contribution remained significantly higher among infants who breastfed at least 75% daily (Figure 1). Bacterial diversity and composition changes were associated with the proportion of daily breast milk intake in a dose-dependent manner. Breast milk contained bacteria with high abundance in gene families associated with membrane transport and carbohydrate, amino acid and energy metabolism (Figure 2). Infants who breastfeed for >75% of their daily milk intake have functionally lower energy metabolism and glycan biosynthesis and metabolism (Figure 3).
Our data provides evidence that mother's breast milk microbes seed the infant's gut. The amount of breastfeeding significantly influences the microbial composition and function, underscoring the importance of breastfeeding in the infant gut microbial maturation process.
P. S. Pannaraj,
C. Cerini, None
J. Bender, None
K. Bittinger, None
A. Bailey, None
A. Rollie, None
H. Adisetiyo, None
C. Santiskulvong, None
F. Bushman, Microbiota Therapeutics: Shareholder , shares
Federal Trade Commission: Consultant , Salary
Biocept: scientific co-founder , shares
Merck: Consultant , Salary
J. Sleasman, None
G. Aldrovandi, None