Microbial Adaptation in Human Milk: Unraveling the Effects of Gestational Age and Lactation Stage Among Indian Mothers

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Introduction Human milk once considered sterile is a habitat for a diverse microbiome. Breast milk is vital in the formation of the newborn microbiome and affects various health outcomes. Its microbiota is influenced by mode of delivery, geographic location, mastitis, diet, obesity, and gestational age and lactation stage. Knowledge of region-wise data regarding human milk microbiome is the need of an hour. Purpose The aim of this study was to isolate and characterize breast milk microbiome and to know the effect of gestational age and lactation stage on it. Methods A prospective longitudinal study included 30 mothers, of whom 10 were of gestational age < 32 weeks, 10 between 32 and 36 6/7 weeks, and the remaining 10 above 37 weeks of gestation at the time of delivery. Milk samples were collected and analyzed for microbiome at three different time points, that is, colostrum, transition milk (7-9 days), and mature milk (after 14 days). Results 381bacterial colonies were isolated and 242 colonies were identified by matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) and cross-verified with 16s RNA sequencing, which included 38 different bacterial species. The majority of colonies (229/242) identified belonged to 4 phyla- firmicutes 119 (51.97%), proteobacteria 48 (20.96%), Bacillota 41 (17.9%), and actinobacteria 21 (9.17%). Bacterial diversity increased with gestational age and lactation stage and the proportion of actinobacteria and Bacillota increased significantly with lactation stage ( P value −.039), showing that preterm mother’s milk has a lesser quantity of beneficial bacteria. Conclusion This study provided the insight into effect of gestational age and lactation stage on breast milk microbiome. The diversity of milk microbiome increases with lactation and gestational age; however, the preterm mother’s milk lacks sufficient beneficial bacteria.