Characterization of the Diversity and Temporal Stability of Bacterial Communities in Human Milk

TLDR

Human milk contains diverse bacterial genera, yet its full diversity and temporal stability remain poorly characterized, raising questions about its role in infant gut colonization and mammary health. The study aimed to comprehensively characterize the human milk microbiome using 16S rRNA pyrosequencing. The authors performed 16S rRNA pyrosequencing on milk samples from 16 women collected at three time‑points over four weeks to profile bacterial communities. Milk bacterial communities were complex, with several genera exceeding 5% abundance, and were often stable over time within individuals, confirming that human milk harbors greater bacterial diversity than previously reported.

Abstract

Recent investigations have demonstrated that human milk contains a variety of bacterial genera; however, as of yet very little work has been done to characterize the full diversity of these milk bacterial communities and their relative stability over time. To more thoroughly investigate the human milk microbiome, we utilized microbial identification techniques based on pyrosequencing of the 16S ribosomal RNA gene. Specifically, we characterized the bacterial communities present in milk samples collected from 16 women at three time-points over four weeks. Results indicated that milk bacterial communities were generally complex; several genera represented greater than 5% of the relative community abundance, and the community was often, yet not always, stable over time within an individual. These results support the conclusion that human milk, which is recommended as the optimal nutrition source for almost all healthy infants, contains a collection of bacteria more diverse than previously reported. This finding begs the question as to what role this community plays in colonization of the infant gastrointestinal tract and maintaining mammary health.