The preterm human milk microbiota fluctuates by postpartum week and is characterized by gestational age and maternal BMI

ABSTRACTEvidence suggests that the type of nutrition fed to preterm infants influences their intestinal microbiome and immunity. However, few studies have conducted a longitudinal analysis of the microbiota of mother’s own milk (MOM) and the factors shaping its composition. Furthermore, the microbiota of pasteurized donor human milk (PDHM) and infant formula have not been extensively investigated. Here, we examine the microbiota of 238 MOM, 30 PDHM, and 73 formula samples from a cohort of 72 preterm infants using 16S rRNA sequencing. We find differences in the microbial diversity and composition between nutrition types. Additionally, we demonstrate that the microbiota of MOM exhibits temporal fluctuations and has associations with several maternal factors. Lastly, we identify three microbiota community clusters within MOM—termed lactotypes—that have distinct taxonomic compositions and maternal factors. Collectively, our findings lay the foundation for exploring the relationship between the microbiota of nutrition and preterm infant health outcomes.IMPORTANCEDespite a growing recognition that the type of nutrition received by preterm infants influences their intestinal microbiome and health outcomes, the microbiota of mother's own milk (MOM), pasteurized donor human milk (PDHM), and infant formula remain poorly characterized. In our study, we found that the structure of microbial communities, bacterial diversity, and relative abundances of specific genera were significantly different between MOM, PDHM, and formula. Additionally, our results suggest that the microbiota of MOM changes as a function of time and maternal factors. Lastly, we identified three lactotypes within MOM that have distinct microbial compositions and described the maternal factors associated with them. These findings set the stage for future research aimed at advancing our knowledge of the microbiota of preterm infant nutrition and the specific influence it may have on health outcomes.