Bacterial microbiome of breast milk and child saliva from low-income Mexican-American women and children.

Background: The childhood salivary microbiome, which plays an important role in healthy development, may be influenced by breast milk consumption. The composition of the milk microbiome and the role it plays in the establishment of the infant microbiome are not well understood.

Methods: Here, we sequenced the bacterial 16S rRNA gene to characterize microbial communities in breast milk and 5-year-old child saliva from 10 low-income, Mexican-American mother-child pairs with a high prevalence of obesity.

Results: Members of the genus Streptococcus dominated both milk and salivary microbial communities in most subjects. Staphylococcus was observed predominately in milk samples while Prevotella was more prevalent in child saliva. No statistically significant relationships were observed between maternal and child microbiomes or between child microbiome and BMI. However, prepregnancy BMI was correlated with both lower Streptococcus abundance (r = -0.67) and higher microbial diversity (r = 0.77) in breast milk (P < 0.05 for both). Diversity estimates were notably similar to data from other low-income cohorts or children.

Conclusion: These findings contribute to the currently limited state of knowledge regarding the breast milk and salivary microbiomes in mother-child pairs and may inform future studies seeking to elucidate the relationship between early-life microbial exposures and pediatric health.