Microbiome in breast milk
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The Microbiome in Breast Milk: Composition, Influences, and Implications
Introduction to Breast Milk Microbiome
Breast milk is not only a source of essential nutrients for infants but also a complex and dynamic microbiome that plays a crucial role in infant health. This microbiome includes a diverse array of bacteria, fungi, archaea, eukaryotes, and viruses, which contribute to the development of the infant gut microbiota and immune system .
Composition of Breast Milk Microbiota
Bacterial Diversity and Dominant Genera
Breast milk contains a higher bacterial diversity compared to infant or maternal feces, with studies identifying up to 58 phyla, 133 classes, 263 orders, 596 families, 590 genera, and 1300 species. The most frequently found bacterial genera include Staphylococcus, Streptococcus, Lactobacillus, Pseudomonas, Bifidobacterium, Corynebacterium, Enterococcus, Acinetobacter, Rothia, Cutibacterium, Veillonella, and Bacteroides .
Fungal, Archaeal, and Viral Components
In addition to bacteria, breast milk also contains fungal, archaeal, eukaryotic, and viral DNA, indicating a complex microbial ecosystem.
Factors Influencing Breast Milk Microbiota
Maternal and Environmental Factors
Several factors influence the composition of the breast milk microbiota, including gestational age, delivery mode, biological sex of the infant, parity, intrapartum antibiotics, lactation stage, maternal diet, BMI, HIV infection, geographic location, and collection/feeding methods . For instance, milk from obese mothers tends to have a different and less diverse bacterial community compared to milk from normal-weight mothers. Additionally, the mode of delivery, particularly elective cesarean sections, can significantly alter the milk microbiota .
Temporal Changes
The microbiome of breast milk changes over the course of lactation. Colostrum is predominantly inhabited by Weisella, Leuconostoc, Staphylococcus, Streptococcus, and Lactococcus, while milk at 1 and 6 months postpartum shows an increase in typical oral cavity inhabitants like Veillonella, Leptotrichia, and Prevotella.
Impact on Infant Health
Gut Microbiota Development
Breastfeeding significantly influences the early development of the infant gut microbiota. Infants who receive a higher proportion of their daily milk intake from breastfeeding have gut microbial communities more closely related to their mother's milk and skin microbiota. This vertical transfer of bacteria from mother to infant is crucial for establishing a healthy gut microbiome, which has lifelong implications for health and immunity .
Immune System Modulation
Breast milk contains human milk oligosaccharides (HMOs) and extracellular vesicles (EVs) that play a role in preventing pathogenic bacterial adhesion and providing nutrition for the microbiome. These components are thought to guide the infant's developing mucosal immune system.
Probiotic Supplementation
Maternal Probiotic Supplementation
Studies have explored the potential of modulating the breast milk microbiota through maternal probiotic supplementation. However, supplementation with specific probiotics like Lactobacillus rhamnosus GG, Lactobacillus acidophilus La-5, and Bifidobacterium animalis ssp. lactis Bb-12 did not significantly affect the overall composition of the breast milk microbiota.
Conclusion
The microbiome in breast milk is a complex and dynamic ecosystem influenced by various maternal and environmental factors. It plays a crucial role in the development of the infant gut microbiota and immune system. Understanding the composition and influences on the breast milk microbiota can help in developing interventions to improve infant health, such as targeted probiotic supplementation. Further research is needed to fully uncover the biological roles and potential health benefits of the diverse microbial communities present in breast milk.
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