(P19-008-25) Associations Between Relative Abundances of Fatty Acids in Human Milk and Bacterial Genera in Infant Feces and Saliva

Objectives: Because oral and gastrointestinal microbiomes of breastfed infants may be influenced by fatty acid profiles of the human milk they consume, we investigated relationships between human milk fatty acids and microbial genera in infant saliva and feces. Based on previously published data (some in adults), we tested the hypotheses that relative abundance of Streptococcus in infant saliva is negatively correlated with relative amount of saturated fatty acids (SFA) in milk; and that Lactobacillus in infant feces is positively correlated with 16:1 and 18:2n6 and negatively correlated with 22:6n3 in milk.

Methods: Human milk and infant saliva and feces were collected from 21 breastfeeding mother-infant dyads at 9 timepoints between 2 days and 6 months postpartum. Relative abundances of fatty acids in milk were determined using gas chromatography, and values were averaged across timepoints. Fecal and oral microbiomes were characterized by sequencing the V1-V3 regions of the 16S ribosomal RNA (rRNA) gene, and values averaged across timepoints. Spearman rank correlations were calculated using R; P< 0.05 was declared as significant.

Results: Data do not support the hypotheses. However, other associations were observed. In infant saliva, Porphyromonas was positively correlated with 22:2 in milk and Propionibacterium negatively correlated with 24:0. In feces, Bifidobacterium was positively correlated with 6:0, 15:1 c10, and 18:1 t10 in milk. Escherichia shigella in feces was negatively correlated with 17:1 c10 in milk. Parabacteriodes in feces was positively correlated with 18:1 t10 in milk, and Lactococcus in feces was positively correlated with 18:3n3.

Conclusions: Relative abundances of some fatty acids in human milk are correlated with those of selected bacterial genera in infant feces and saliva. These findings suggest that oral and gastrointestinal microbiomes of breastfeeding infants might be impacted by the fatty acid composition of the human milk they consume.

Funding Sources: Bill and Melinda Gates Foundation, Idaho Agricultural Experiment Station, NIH (P20GM152304)