Unveiling the dynamics of the breast milk microbiome: impact of lactation stage and gestational age

Abstract

Background Breast milk (BM) provides complete nutrition for infants for the first six months of life and is essential for the development of the newborn’s immature immune and digestive systems. While BM was conventionally believed to be sterile, recent advanced high throughput technologies have unveiled the presence of diverse microbial communities in BM. These insights into the BM microbiota have mainly originated from uncomplicated pregnancies, possibly not reflecting the circumstances of mothers with pregnancy complications like preterm birth (PTB). Methods In this article, we investigated the BM microbial communities in mothers with preterm deliveries (before 37 weeks of gestation). We compared these samples with BM samples from healthy term pregnancies across different lactation stages (colostrum, transitional and mature milk) using 16S rRNA gene sequencing. Results Our analysis revealed that the microbial communities became increasingly diverse and compositionally distinct as the BM matured. Specifically, mature BM samples were significantly enriched in Veillonella and lactobacillus (Kruskal Wallis; p < 0.001) compared to colostrum. The comparison of term and preterm BM samples showed that the community structure was significantly different between the two groups (Bray Curtis and unweighted unifrac dissimilarity; p < 0.001). Preterm BM samples exhibited increased species richness with significantly higher abundance of Staphylococcus haemolyticus, Propionibacterium acnes, unclassified Corynebacterium species. Whereas term samples were enriched in Staphylococcus epidermidis, unclassified OD1, and unclassified Veillonella among others. Conclusion Our study underscores the significant influence of pregnancy-related complications, such as preterm birth (before 37 weeks of gestation), on the composition and diversity of BM microbiota. Given the established significance of the maternal microbiome in shaping child health outcomes, this investigation paves the way for identifying modifiable factors that could optimize the composition of BM microbiota, thereby promoting maternal and infant health.

Assembly, stability, and dynamics of the infant gut microbiome are linked to bacterial strains and functions in mother’s milk

“…1B). This is consistent with previous studies showing detecting skin-associated taxa in milk in addition to Bifidobacteria 32,33 .…”

Human Breast Milk: The Role of Its Microbiota and Metabolites in Infant Health

“…54 As breastfeeding continues, the microbial diversity within the milk increases, and beneficial bacteria, such as Veillonella, Bif idobacterium, and Streptococcus, proliferate and colonize the neonatal gut. 32,38,55 This dynamic transition is linked to the infant's growth and development, underpinning the stability and evolution of the gut microbiota. 32,55,56 During the 3−4 month postpartum period, the microbial composition of breast milk undergoes dynamic changes, primarily shifting between Proteobacteria and Firmicutes.…”

“…Damaceno et al (2017) analyzed breast milk microbiota quantitatively and found that colostrum has a higher absolute number of bacteria (3.9 log 10 CFU/mL), with Staphylococcus epidermidis being the most abundant . As breastfeeding continues, the microbial diversity within the milk increases, and beneficial bacteria, such as Veillonella , Bifidobacterium , and Streptococcus , proliferate and colonize the neonatal gut. ,, This dynamic transition is linked to the infant’s growth and development, underpinning the stability and evolution of the gut microbiota. ,, …”

“…Current research has revealed a variety of breast milk-associated microbes, including Bifidobacterium , Lactobacillus , Akkermansia , Staphylococcus , Streptococcus , Veillonella , Weisella , Alloiococcus , Pseudomonas , Leuconostoc , Lactococcus , Acinetobacter , Corynebacterium , Propionibacterium , Rothia , and even phages − (Figure ). Many of these microbes are lactic acid bacteria and play an important role in human milk. ,− Their significance extends beyond maintaining a balanced gut microbiota; they also demonstrate efficacy in combating pathogenic microorganisms. , In 2010, Martin and colleagues employed PCR-denaturing gradient gel electrophoresis and quantitative real-time PCR to study breast milk bifidobacterial communities .…”

Residents or Tourists: Is the Lactating Mammary Gland Colonized by Residential Microbiota?

“…While human milk was initially assumed to be a sterile fluid, it is now widely accepted as a source of beneficial bacteria for infants, with around 10 4 colony-forming units per mL [1]. The human milk microbiome exhibits a low richness of bacteria, with Staphylococcus and Streptococcus being the most abundant and prevalent genera [2][3][4][5][6]. The remaining portion is comprised of other typical skin and oral taxa, including Corynebacterium and Cutibacterium [7], as well as lactic acid-producing bacteria such as Bifidobacterium and Lactobacillaceae, which are considered to contribute to infant health via their production of immune-modulating metabolites [8].…”