Origins of human milk microbiota: new evidence and arising questions

Interembodiment beyond kin: Leveraging partibility within microbial FemTech

Contextualized within paradigm shifts in biological sciences toward reimagining reproductive health as entangled with microbial bodies, we engage interembodiment to underscore central tensions within projects leveraging the promises of the gendered microbiome. With research demonstrating that maternal vaginal microbes first "seed" infants' immuno-development and then dynamic relations at the breast develop it, microbes and their relations become reframed as a kind of intergenerational biocultural "inheritance." This inheritance is experienced through microbiopolitical demands for a "good vagina" or the incitement to breastfeed-what we term a chimeric imperative-but is also framed as potentially severable, replicable, and redistributable. Returning to Strathern's theorizing about how the body's porosity facilitates such partible detachments and reattachments, we analyze four companies' projects that exploit microbes' dynamic potential to address persistent gendered health gaps. We argue that newly relational ideas about embodiment reconceptualize the biopolitical demands of and on the reproductive body, guide how venture-tech companies seek to address persistent technical and ethical challenges, and reconceptualize how people form biosocial connections across bodies. Taking microbes' partible nature seriously highlights these intergenerational transfers as ongoing and full of possibility for a range of people; enabling not only expected attachments, but also other shared embodiments potentially distributed beyond the skin.

Viable bacterial communities in freshly pumped human milk and their changes during cold storage conditions

BACKGROUND

Human milk harbors diverse bacterial communities that contribute to infant health. Although pumping and storing milk is a common practice, the viable bacterial composition of pumped milk and the impact of storage practice on these bacteria remains under-explored. This metagenomic observational study aimed to characterize viable bacterial communities in freshly pumped human milk and its changes under different storage conditions.

METHODS

In 2023, twelve lactating mothers from the CELSPAC: TNG cohort (Czech Republic) provided freshly pumped milk samples. These samples were stored under various conditions (refrigeration for 24 h, 48 h, or freezing for six weeks) and treated with propidium monoazide (PMA) to selectively identify viable cells. The DNA extracted from individual samples was subsequently analyzed using 16S rRNA amplicon sequencing on the Illumina platform.

RESULTS

The genera Streptococcus, Staphylococcus, Diaphorobacter, Cutibacterium, and Corynebacterium were the most common viable bacteria in fresh human milk. The median sequencing depth and Shannon index of fresh human milk samples treated with PMA (+ PMA) were significantly lower than in untreated (-PMA) samples (p < 0.05 for all), which was true also for each time point. Also, significant changes in these parameters were observed between fresh human milk samples and their paired frozen samples (p < 0.05), while no differences were found between fresh human milk samples and those refrigerated for up to 48 h (p > 0.05). Of specific genera, only + PMA frozen human milk samples showed a significant decrease in the central log-ratio transformed relative abundances of the genera Diaphorobacter and Cutibacterium (p < 0.05) in comparison to + PMA fresh human milk samples.

CONCLUSIONS

The study demonstrated that the bacterial profiles significantly differed between human milk samples treated with PMA, which represent only viable bacteria, and those untreated. While storage at 4 °C for up to 48 h did not significantly alter the overall diversity and composition of viable bacteria in human milk, freezing notably affected both the viability and relative abundances of some bacterial genera.

Composition of the fecal, vaginal and colostrum microbiotas of dams at parturition and their relationship with neonatal outcomes in dogs

BACKGROUND

Microbial seeding in early life is critical for the host's short- and long-term health, and the mother is the first source of bacteria for the newborn. The objective of this study was to characterize the maternal fecal, vaginal, and colostral microbiotas in the canine species one day after parturition and to evaluate the relationship between the microbial profiles of 36 dams and the neonatal outcomes of 284 newborns.

RESULTS

The first part of the study revealed the presence of 2 fecal, 3 vaginal, and 2 colostral microbial clusters on the basis of the core microbiota of the dams. Among these three maternal microbiotas, only the vaginal microbiome was found to be associated with neonatal outcomes. Compared with those in the other clusters, females in Cluster 1, with the lowest stillbirth and neonatal mortality ratios, presented a greater abundance of Moraxellaceae in their vaginal microbiota; Cluster 2, with a greater abundance of Pasteurellaceae, mostly from the Haemophilus genus; and Cluster 3 (with the highest stillbirth and neonatal mortality ratios), a greater abundance of Enterobacteriaceae, mostly E. coli. Moreover, Cluster 3 dams presented significantly lower species richness according to the Shannon index than did dams from the other clusters.

CONCLUSIONS

This study underscores the strong association between maternal microbiota, particularly the vaginal microbiota, and newborn health. The results of this study call for further research to gain a deeper understanding of the optimal vaginal microbiota composition in canine species and the ways to modulate it to improve neonatal outcomes.

Integrating the milk microbiome signatures in mastitis: milk-omics and functional implications

Mammalian milk contains a variety of complex bioactive and nutritional components and microorganisms. These microorganisms have diverse compositions and functional roles that impact host health and disease pathophysiology, especially mastitis. The advent and use of high throughput omics technologies, including metagenomics, metatranscriptomics, metaproteomics, metametabolomics, as well as culturomics in milk microbiome studies suggest strong relationships between host phenotype and milk microbiome signatures in mastitis. While single omics studies have undoubtedly contributed to our current understanding of milk microbiome and mastitis, they often provide limited information, targeting only a single biological viewpoint which is insufficient to provide system-wide information necessary for elucidating the biological footprints and molecular mechanisms driving mastitis and milk microbiome dysbiosis. Therefore, integrating a multi-omics approach in milk microbiome research could generate new knowledge, improve the current understanding of the functional and structural signatures of the milk ecosystem, and provide insights for sustainable mastitis control and microbiome management.

Human milk oligosaccharides: bridging the gap in intestinal microbiota between mothers and infants

Breast milk is an essential source of infant nutrition. It is also a vital determinant of the structure and function of the infant intestinal microbial community, and it connects the mother and infant intestinal microbiota. Human milk oligosaccharides (HMOs) are a critical component in breast milk. HMOs can reach the baby's colon entirely from milk and become a fermentable substrate for some intestinal microorganisms. HMOs can enhance intestinal mucosal barrier function and affect the intestinal function of the host through immune function, which has a therapeutic effect on specific infant intestinal diseases, such as necrotizing enterocolitis. In addition, changes in infant intestinal microbiota can reflect the maternal intestinal microbiota. HMOs are a link between the maternal intestinal microbiota and infant intestinal microbiota. HMOs affect the intestinal microbiota of infants and are related to the maternal milk microbiota. Through breastfeeding, maternal microbiota and HMOs jointly affect infant intestinal bacteria. Therefore, HMOs positively influence the establishment and balance of the infant microbial community, which is vital to ensure infant intestinal function. Therefore, HMOs can be used as a supplement and alternative therapy for infant intestinal diseases.

Human Milk Archaea Associated with Neonatal Gut Colonization and Its Co-Occurrence with Bacteria

Archaea have been identified as early colonizers of the human intestine, appearing from the first days of life. It is hypothesized that the origin of many of these archaea is through vertical transmission during breastfeeding. In this study, we aimed to characterize the archaeal composition in samples of mother-neonate pairs to observe the potential vertical transmission. We performed a cross-sectional study characterizing the archaeal diversity of 40 human colostrum-neonatal stool samples by next-generation sequencing of V5-V6 16S rDNA libraries. Intra- and inter-sample analyses were carried out to describe the Archaeal diversity in each sample type. Human colostrum and neonatal stools presented similar core microbiota, mainly composed of the methanogens Methanoculleus and Methanosarcina. Beta diversity and metabolic prediction results suggest homogeneity between sample types. Further, the co-occurrence network analysis showed associations between Archaea and Bacteria, which might be relevant for these organisms' presence in the human milk and neonatal stool ecosystems. According to relative abundance proportions, beta diversity, and co-occurrence analyses, the similarities found imply that there is vertical transmission of archaea through breastfeeding. Nonetheless, differential abundances between the sample types suggest other relevant sources for colonizing archaea to the neonatal gut.

Maternal Allergic Disease Phenotype and Infant Birth Season Influence the Human Milk Microbiome

Early infancy is a critical period for immune development. In addition to being the primary food source during early infancy, human milk also provides multiple bioactive components that shape the infant gut microbiome and immune system and provides a constant source of exposure to maternal microbiota. Given the potential interplay between allergic diseases and the human microbiome, this study aimed to characterise the milk microbiome of allergic mothers. Full-length 16S rRNA gene sequencing was performed on milk samples collected at 3 and 6 months postpartum from 196 women with allergic disease. Multivariate linear mixed models were constructed to identify the maternal, infant, and environmental determinants of the milk microbiome. Human milk microbiome composition and beta diversity varied over time (PERMANOVA R2 = 0.011, p = 0.011). The season of infant birth emerged as the strongest determinant of the microbiome community structure (PERMANOVA R2 = 0.014, p = 0.011) with impacts on five of the most abundant taxa. The milk microbiome also varied according to the type of maternal allergic disease (allergic rhinitis, asthma, atopic dermatitis, and food allergy). Additionally, infant formula exposure reduced the relative abundance of several typical oral taxa in milk. In conclusion, the milk microbiome of allergic mothers was strongly shaped by the season of infant birth, maternal allergic disease phenotype, and infant feeding mode. Maternal allergic disease history and infant season of birth should therefore be considered in future studies of infant and maternal microbiota. Trial Registration: ClinicalTrials.gov identifier: ACTRN12606000281594.

Microbial profiling, antimicrobial resistance surveillance, and molecular detection of MecA gene in Staphylococcal strains from donor human milk: Insights from a milk bank investigation

PURPOSE

Donor human milk (DHM) from milk banks provides vital nutrition to vulnerable infants. Understanding its microbial profile and antimicrobial resistance patterns is crucial for ensuring its safety and efficacy. This study aimed to profile the microbial composition, detect antibiotic resistance, and identify the presence of mecA gene in Staphylococcal strains from DHM samples.

MATERIALS AND METHOD

A total of 151 DHM samples were collected from a regional human milk bank in North India. Microbial identification was performed using MALDI TOF MS, and antimicrobial susceptibility testing was conducted using the disc diffusion method. Molecular methods, including PCR, were employed for mecA gene detection.

RESULTS

The study revealed a diverse microbial profile, with Staphylococcus species being predominant. Acinetobacter and Pseudomonas species were also prevalent, raising concerns due to their association with healthcare-associated outbreaks. High rates of antibiotic resistance were observed across both Gram-positive and Gram-negative bacteria, with resistance to commonly used antibiotics such as penicillin, clindamycin, erythromycin, and ceftriaxone. The mecA gene, associated with methicillin resistance, was detected in a significant proportion of Staphylococcal isolates.

CONCLUSION

The study underscores the importance of rigorous microbial analysis and antimicrobial susceptibility testing in assessing the safety of DHM. The presence of diverse microbial species, including antibiotic-resistant strains and the mecA gene in Staphylococcal strains, emphasizes the need for stringent hygiene practices and continuous surveillance in milk banks. Implementing comprehensive screening protocols and adhering to best practices in milk handling and pasteurization are crucial for safeguarding the health of vulnerable infants reliant on donor milk.

Bacterial Community of Breast Milk in Breastfeeding Women Using Culture-Dependent and Culture-Independent Approaches

This study aimed to analyze bacterial communities in breast milk obtained from five breastfeeding women. Culture-dependent and culture-independent methods were used to analyze microbial communities. Total bacterial count of breast milk determined using plate count agar ranged from 3.3 × 104 ± 3.5 × 102 colony forming unit (CFU)/g to 1.7 × 105 ± 3.5 × 103 CFU/g, with a pH between 6.4 and 6.8. Only three species, Leuconostoc citreum (17 out of 160 strains; 10.63%), Staphylococcus epidermidis (118 strains; 73.75%), and Staphylococcus lugdunensis (25 strains; 15.63%), belong to the phylum Bacillota were detected by culture-dependent analysis. Microbial communities analyzed via pyrosequencing revealed greater diversity compared to the culture-dependent analysis. At the phylum level, Bacillota accounted for 60.9% of the microbial community. At the genus level, Staphylococcus (24.57%), Streptococcus (22.93%), and Methylobacterium (8.76%) were dominant genera. While pyrosequencing demonstrated greater microbial diversity than the agar plate culture method, identified microbes might lack information or include many unculturable microbes. Most of all, considering the low total bacterial count averaging 7.2 × 104 CFU/g, further research is needed to determine the significance of microbial presence in breast milk.

Influence of Early Life Factors on the Breast Milk and Fecal Microbiota of Mother-Newborn Dyads

Maternal gut and breast milk (BM) are key in vertically transmission bacteria to infants, shaping their gut microbiota in early life. Although the establishment of early gut microbiota is known, the role of the combined influence of maternal factors and newborn characteristics is not explored. In this study, we aimed to assess the influence of maternal BMI and total body fat, age, delivery mode, and newborn sex on the diversity and composition of the BM and gut microbiota (GM) in mother-newborn dyads. In this cross-sectional study, of the 986 pregnant women candidates, 53 participated, and, finally, 40 mother-newborn dyads exclusively breastfeeding at 20-28 days postpartum were included. Metataxonomic profiling of DNA extracted from BM and fecal samples was conducted using 16S rRNA sequencing. Globally, the findings offer valuable insights that excessive adiposity, age, and C-section delivery influence a lower abundance of specific taxa in the BM, maternal gut, and gut of newborns. Also, the simultaneous analysis of maternal factors and newborn characteristics shows that maternal age and newborn sex explain an important variation in the microbiota composition. These results add to the understanding of the intricate interplay between maternal factors and the microbial communities that influence early-life gut and BM microbiota.

Mother's milk microbiota is associated with the developing gut microbial consortia in very-low-birth-weight infants

Mother's milk contains diverse bacterial communities, although their impact on microbial colonization in very-low-birth-weight (VLBW, <1,500 g) infants remains unknown. Here, we examine relationships between the microbiota in preterm mother's milk and the VLBW infant gut across initial hospitalization (n = 94 mother-infant dyads, 422 milk-stool pairs). Shared zero-radius operational taxonomic units (zOTUs) between milk-stool pairs account for ∼30%-40% of zOTUs in the VLBW infant's gut. We show dose-response relationships between intakes of several genera from milk and their concentrations in the infant's gut. These relationships and those related to microbial sharing change temporally and are modified by in-hospital feeding practices (especially direct breastfeeding) and maternal-infant antibiotic use. Correlations also exist between milk and stool microbial consortia, suggesting that multiple milk microbes may influence overall gut communities together. These results highlight that the mother's milk microbiota may shape the gut colonization of VLBW infants by delivering specific bacteria and through intricate microbial interactions.

Microbiome-Stealth Regulator of Breast Homeostasis and Cancer Metastasis

Cumulative evidence attests to the essential roles of commensal microbes in the physiology of hosts. Although the microbiome has been a major research subject since the time of Luis Pasteur and William Russell over 140 years ago, recent findings that certain intracellular bacteria contribute to the pathophysiology of healthy vs. diseased tissues have brought the field of the microbiome to a new era of investigation. Particularly, in the field of breast cancer research, breast-tumor-resident bacteria are now deemed to be essential players in tumor initiation and progression. This is a resurrection of Russel's bacterial cause of cancer theory, which was in fact abandoned over 100 years ago. This review will introduce some of the recent findings that exemplify the roles of breast-tumor-resident microbes in breast carcinogenesis and metastasis and provide mechanistic explanations for these phenomena. Such information would be able to justify the utility of breast-tumor-resident microbes as biomarkers for disease progression and therapeutic targets.

Probio-M9, a breast milk-originated probiotic, alleviates mastitis and enhances antibiotic efficacy: Insights into the gut-mammary axis

Breast milk naturally contains lactic acid bacteria, but their precise origin remains a subject of debate. In this study, we utilized a rat mastitis animal model to investigate the potential of a breast milk-derived probiotic strain, Lacticaseibacillus rhamnosus Probio-M9, in alleviating mastitis and enhancing the efficacy of antibiotic treatment. Through histopathological analysis of mammary tissue, we observed that Probio-M9 effectively relieved mastitis, mitigated inflammation, and improved the response to antibiotic treatment. Metagenomic analysis further revealed that Probio-M9 enhanced interactions among gut microbes, accompanied by an increase in the relative abundance of Ruminococcaceae and the regulation of specific genes and carbohydrate-active enzymes, subsequently impacting host immunity. Additionally, an intriguing finding was the translocation of live Probio-M9 from the gut to the mammary tissue only during bacterial mastitis and lactation, likely facilitated through lymphatic circulation. These findings advance our understanding of the intricate gut-mammary axis and provide valuable insights into the potential health benefits of probiotic interventions.

Development of systemic and mucosal immune responses against gut microbiota in early life and implications for the onset of allergies

The early microbial colonization of human mucosal surfaces is essential for the development of the host immune system. Already during pregnancy, the unborn child is prepared for the postnatal influx of commensals and pathogens via maternal antibodies, and after birth this protection is continued with antibodies in breast milk. During this critical window of time, which extends from pregnancy to the first year of life, each encounter with a microorganism can influence children's immune response and can have a lifelong impact on their life. For example, there are numerous links between the development of allergies and an altered gut microbiome. However, the exact mechanisms behind microbial influences, also extending to how viruses influence host-microbe interactions, are incompletely understood. In this review, we address the impact of infants' first microbial encounters, how the immune system develops to interact with gut microbiota, and summarize how an altered immune response could be implied in allergies.

Revealing the diversity of endogenous peptides and parent proteins in human colostrum and mature milk through peptidomics analysis

Endogenous peptides and their parent proteins are important nutritional components with diverse biological functions. The objective of this study was to analyze and compare endogenous peptides and parent proteins found in human colostrum (HC) and human mature milk (HM) using a 4D label-free technique. In total, 5162 and 940 endogenous peptides derived from 258 parent proteins were identified in human milk by database (DB) search and de novo, respectively. Among these peptides, 2446 differentially expressed endogenous peptides with various bioactivities were identified. The Gene Ontology analysis unveiled the cellular components, biological processes, and molecular functions associated with these parent proteins. Metabolic pathway analysis suggested that neutrophil extracellular trap formation had the greatest significance with 24 parent proteins. These findings will offer a fresh perspective on the development of infant formula powder, highlighting the potential for incorporating these changes to enhance its nutritional composition and benefits.

Vertical Transfer of Maternal Gut Microbes to Offspring of Western Diet-Fed Dams Drives Reduced Levels of Tryptophan Metabolites and Postnatal Innate Immune Response

Maternal obesity and/or Western diet (WD) is associated with an increased risk of metabolic dysfunction-associated steatotic liver disease (MASLD) in offspring, driven, in part, by the dysregulation of the early life microbiome. Here, using a mouse model of WD-induced maternal obesity, we demonstrate that exposure to a disordered microbiome from WD-fed dams suppressed circulating levels of endogenous ligands of the aryl hydrocarbon receptor (AHR; indole, indole-3-acetate) and TMAO (a product of AHR-mediated transcription), as well as hepatic expression of Il10 (an AHR target), in offspring at 3 weeks of age. This signature was recapitulated by fecal microbial transfer from WD-fed pregnant dams to chow-fed germ-free (GF) lactating dams following parturition and was associated with a reduced abundance of Lactobacillus in GF offspring. Further, the expression of Il10 was downregulated in liver myeloid cells and in LPS-stimulated bone marrow-derived macrophages (BMDM) in adult offspring, suggestive of a hypo-responsive, or tolerant, innate immune response. BMDMs from adult mice lacking AHR in macrophages exhibited a similar tolerogenic response, including diminished expression of Il10. Overall, our study shows that exposure to maternal WD alters microbial metabolites in the offspring that affect AHR signaling, potentially contributing to innate immune hypo-responsiveness and progression of MASLD, highlighting the impact of early life gut dysbiosis on offspring metabolism. Further investigations are warranted to elucidate the complex interplay between maternal diet, gut microbial function, and the development of neonatal innate immune tolerance and potential therapeutic interventions targeting these pathways.

Local environment shapes milk microbiomes while evolutionary history constrains milk macronutrients in captive cercopithecine primates

Milk is a complex biochemical fluid that includes macronutrients and microbiota, which, together, are known to facilitate infant growth, mediate the colonization of infant microbiomes, and promote immune development. Examining factors that shape milk microbiomes and milk-nutrient interplay across host taxa is critical to resolving the evolution of the milk environment. Using a comparative approach across four cercopithecine primate species housed at three facilities under similar management conditions, we test for the respective influences of the local environment (housing facility) and host species on milk (a) macronutrients (fat, sugar, and protein), (b) microbiomes (16S rRNA), and (c) predicted microbial functions. We found that milk macronutrients were structured according to host species, while milk microbiomes and predicted function were strongly shaped by the local environment and, to a lesser extent, host species. The milk microbiomes of rhesus macaques (Macaca mulatta) at two different facilities more closely resembled those of heterospecific facility-mates compared to conspecifics at a different facility. We found similar, facility-driven patterns of microbial functions linked to physiology and immune modulation, suggesting that milk microbiomes may influence infant health and development. These results provide novel insight into the complexity of milk and its potential impact on infants across species and environments.

Microbiome: Mammalian milk microbiomes: sources of diversity, potential functions, and future research directions

Abstract

Milk is an ancient, fundamental mammalian adaptation that provides nutrition and biochemical communication to offspring. Microbiomes have been detected in milk of all species studied to date. In this review, we discuss: (a) routes by which microbes may enter milk; (b) evidence for proposed milk microbiome adaptive functions; (c) variation in milk microbiomes across mammals; and (d) future research directions, including suggestions for how to address outstanding questions on the viability and functionality of milk microbiomes. Milk microbes may be sourced from the maternal gastrointestinal tract, oral, skin, and mammary gland microbiomes and from neonatal oral and skin microbiomes. Given the variety of microbial sources, stochastic processes strongly influence milk microbiome assembly, but milk microbiomes appear to be influenced by maternal evolutionary history, diet, environment, and milk nutrients. Milk microbes have been proposed to colonize the neonatal intestinal tract and produce gene and metabolic products that influence physiology, metabolism, and immune system development. Limited epidemiological data indicate that early-life exposure to milk microbes can result in positive, long-term health outcomes. Milk microbiomes can be modified by dietary changes including providing the mother with probiotics and prebiotics. Milk replacers (i.e. infant formula) may benefit from supplementation with probiotics and prebiotics, but data are lacking on probiotics' usefulness, and supplementation should be evidence based. Overall, milk microbiome literature outside of human and model systems is scarce. We highlight the need for mechanistic studies in model species paired with comparative studies across mammals to further our understanding of mammalian milk microbiome evolution. A broader study of milk microbiomes has the potential to inform animal care with relevance to ex situ endangered species.

Lay summary

Milk is an ancient adaptation that supports the growth and development of mammalian neonates and infants. Beyond its fundamental nutritional function, milk influences all aspects of neonatal development, especially immune function. All kinds of milks so far studied have contained a milk microbiome. In this review, we focus on what is known about the collection of bacterial members found in milk microbiomes. Milk microbiomes include members sourced from maternal and infant microbiomes and they appear to be influenced by maternal evolutionary history, diet, milk nutrients, and environment, as well as by random chance. Once a neonate begins nursing, microbes from milk colonize their gut and produce byproducts that influence their physiology, metabolism, and immune development. Empirical data on milk microbiomes outside of humans and model systems are sparse. Greater study of milk microbiomes across mammals will expand our understanding of mammalian evolution and improve the health of animals under human care.

In vitro model of human mammary gland microbial colonization (MAGIC) demonstrates distinctive cytokine response to imbalanced human milk microbiota

Despite the established concept of the human mammary gland (MG) as a habitat with its own microbiota, the exact mechanism of MG colonization is still elusive and a well-characterized in vitro model would reinforce studies of the MG microbiota development. We aimed to establish and characterize an in vitro cell model for studying MAmmary Gland mIcrobial Colonization (MAGIC) model. We used the immortalized cell line MCF10A, which expresses the strong polarized phenotype similar to MG ductal epithelium when cultured on a permeable support (Transwell). We analyzed the surface properties of the MAGIC model by gene expression analysis of E-cadherin, tight junction proteins, and mucins and by scanning electron microscopy. To demonstrate the applicability of the model, we tested the adhesion capability of the whole human milk (HM) microbial community and the cellular response of the model when challenged directly with raw HM samples. MCF10A on permeable supports differentiated and formed a tight barrier, by upregulation of CLDN8, MUC1, MUC4, and MUC20 genes. The surface of the model was covered with mucins and morphologically diverse with at least two cell types and two types of microvilli. Cells in the MAGIC model withstood the challenge with heat-treated HM samples and responded differently to the imbalanced HM microbiota by distinctive cytokine response. The microbial profile of the bacteria adhered on the MAGIC model reflected the microbiological profile of the input HM samples. The well-studied MAGIC model could be useful for studies of bacterial attachment to the MG and for in vitro studies of biofilm formation and microbiota development.IMPORTANCEThe MAGIC model may be particularly useful for studies of bacterial attachment to the surface of the mammary ducts and for in vitro studies of biofilm formation and the development of the human mammary gland (MG) microbiota. The model is also useful for immunological studies of the interaction between bacteria and MG cells. We obtained pioneering information on which of the bacteria present in the raw human milk (HM) were able to attach to the epithelium treated directly with raw HM, as well as on the effects of bacteria on the MG epithelial cells. The MAGIC cell model also offers new opportunities for research in other areas of MG physiology, such as the effects of bioactive milk components on microbial colonization of the MG, mastitis prevention, and studies of probiotic development. Since resident MG bacteria may be an important factor in breast cancer development, the MAGIC in vitro tool also offers new opportunities for cancer research.

Isolation, characterization of Weissella confusa and Lactococcus lactis from different milk sources and determination of probiotic features

This study aimed to investigate the probiotic properties of Lactic Acid Bacteria (LAB) isolates derived from various milk sources. These isolates identified based on their morphological characteristics and 16S rRNA gene sequencing. Four strains of Lactococcus lactis and two strains of Weissella confusa were identified with over 96% 16S rRNA gene similarity according to the NCBI-BLAST results. The survival of the isolates was determined in low pH, pepsin, bile salts, and pancreatin, and their adhesion ability was assessed by in vitro cell adhesion assay, hydrophobicity, auto- and co-aggregation, and safety criteria were determined by hemolytic, gelatinase activities, and DNAse production ability tests. The results showed that the LAB isolates had different levels of resistance to various stress factors. L. lactis subsp. cremoris MH31 showed the highest resistance to bile salt, while the highest pH resistance was observed in L. lactis MH31 at pH 3.0. All the isolates survived in pepsin exposure at pH 3.0 for 3 h. The auto-aggregation test results showed that all strains exhibited auto-aggregation ranging from 84.9 to 91.4%. Co-aggregation percentage ranged from 19 - 54% and 17 - 57% against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213, respectively. The hydrophobicity capacity of the LAB isolated ranged from 35-61%. These isolates showed different adhesion abilities to Caco-2 cells (81.5% to 92.6%). None of the isolates exhibited DNase, gelatinase and hemolytic activity (γ-hemolysis). All results indicate that these LAB strains have the potential to be used as probiotics.

The gut-lung axis and asthma susceptibility in early life

Asthma is the most common chronic disease among children, with more than 300 million cases worldwide. Over the past several decades, asthma incidence has grown, and epidemiological studies identify the modernized lifestyle as playing a strong contributing role in this phenomenon. In particular, lifestyle factors that modify the maternal gut microbiome during pregnancy, or the infant microbiome in early life, can act as developmental programming events which determine health or disease susceptibility later in life. Microbial colonization of the gut begins at birth, and factors such as delivery mode, breastfeeding, diet, antibiotic use, and exposure to environmental bacteria influence the development of the infant microbiome. Colonization of the gut microbiome is crucial for proper immune system development and disruptions to this process can predispose a child to asthma development. Here, we describe the importance of early-life events for shaping immune responses along the gut-lung axis and why they may provide a window of opportunity for asthma prevention.

The Breast Microbiome in Breast Cancer Risk and Progression: A Narrative Review

A decade ago, studies in human populations first revealed the existence of a unique microbial community in the breast, a tissue historically viewed as sterile, with microbial origins seeded through the nipple and/or translocation from other body sites. Since then, research efforts have been made to characterize the microbiome in healthy and cancerous breast tissues. The purpose of this review is to summarize the current evidence for the association of the breast microbiome with breast cancer risk and progression. Briefly, while many studies have examined the breast microbiome in patients with breast cancer, and compared it with the microbiome of benign breast disease tissue or normal breast tissue, these studies have varied widely in their sample sizes, methods, and quality of evidence. Thus, while several large and rigorous cross-sectional studies have provided key evidence of an altered microbiome in breast tumors compared with normal adjacent and healthy control tissue, there are few consistent patterns of perturbed microbial taxa. In addition, only one large prospective study has provided evidence of a relationship between the breast tumor microbiota and cancer prognosis. Future research studies featuring large, well-characterized cohorts with prospective follow-up for breast cancer incidence, progression, and response to treatment are warranted.

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

IMPORTANCE

Despite 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.

Maternal Consumption of Non-Nutritive Sweeteners during Pregnancy Is Associated with Alterations in the Colostrum Microbiota

Non-nutritive sweeteners (NNSs) provide a sweet taste to foods and beverages without significantly adding calories. Still, their consumption has been linked to modifications in adult's and children's gut microbiota and the disruption of blood glucose control. Human milk microbiota are paramount in establishing infants' gut microbiota, but very little is known about whether the consumption of sweeteners can alter it. To address this question, we sequenced DNA extracted colostrum samples from a group of mothers, who had different levels of NNS consumption, using the Ion Torrent Platform. Our results show that the "core" of colostrum microbiota, composed of the genera Bifidobacterium, Blautia, Cutibacteium, Staphylococcus, and Streptococcus, remains practically unchanged with the consumption of NNS during pregnancy, but specific genera display significant alterations, such as Staphylococcus and Streptococcus. A significant increase in the unclassified archaea Methanobrevibacter spp. was observed as the consumption frequency of NNS increased. The increase in the abundance of this archaea has been previously linked to obesity in Mexican children. NNS consumption during pregnancy could be related to changes in colostrum microbiota and may affect infants' gut microbiota seeding and their future health.

Breastmilk microbiome changes associated with lactational mastitis and treatment with dandelion extract

Introduction

Dandelion (Pugongying) is one of the most frequently used Chinese herbs for treating lactational mastitis (LM). Pugongying granules, a patented medication primarily comprised of dandelion extract, have been approved by CFDA for LM treatment in China. The aims of this study were to investigate the etiology of LM and the mechanism by which Pugongying granules decrease LM symptoms, with a particular focus on the microbial communities found in breastmilk.

Methods

Participants were recruited from a previously performed randomized controlled trial (Identifier: NCT03756324, ClinicalTrials.gov). Between 2019 and 2020, women diagnosed with unilateral LM at the Beijing University of Chinese Medicine Third Affiliated Hospital were enrolled. In total, 42 paired breastmilk samples from the healthy and affected breasts of the participants were collected. Additionally, 37 paired pre- and post-treatment breastmilk samples from the affected breast were collected from women who received a 3-day course of either Pugongying granules (20 women) or cefdinir (17 women). Clinical outcomes [e.g., body temperature, visual analogue scale (VAS) score for breast pain, the percentage of neutrophils (NE%)] were analyzed pre- and post-treatment, and the breastmilk samples were subjected to 16S rRNA gene sequencing to analyze the alpha and beta diversities and identify significant bacteria. Finally, the relationship between microorganisms and clinical outcomes was analyzed.

Results

There was no significant difference in fever and pain between the Pugongying group and cefdinir group. The most prevalent bacterial genera in breastmilk were Streptococcus and Staphylococcus. Compared to healthy breastmilk, microbial diversity was reduced in affected breastmilk, and there was a higher relative abundance of Streptococcus. After Pugongying treatment, there was an increase in microbial diversity with significantly higher abundance of Corynebacterium. A negative correlation was found between Corynebacterium, VAS score, and NE%. Treatment with cefdinir did not affect microbial diversity. Taken together, our results show a correlation between LM and reduced microbial diversity, as well as an increased abundance of Streptococcus in affected breastmilk.

Conclusion

Pugongying granules enhanced microbial diversity in breastmilk samples. Given the substantial variation in individual microbiomes, identifying specific species of Streptococcus and Corynebacterium associated with LM may provide additional insight into LM pathogenesis and treatment.

Effects of maternal probiotic supplementation on breast milk microbiome and infant gut microbiome and health: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

The early-life microbiome is formed during the perinatal period and is critical for infants' lifelong health. This is established by maternal-infant microbiome crosstalk, which is mediated by the breast milk microbiome. The milk microbiome is dependent on the maternal gut microbiome, suggesting that it could potentially be restored through oral probiotic supplements. Therefore, we conducted this systematic review and meta-analysis to summarize the effect of maternal probiotic supplements on breast milk and infant gut microbiome composition and on infant health.

DATA SOURCES

The PubMed, EMBASE, Web of Science, Scopus, CINAHL, and Science Direct databases were searched until December 15, 2022.

STUDY ELIGIBILITY CRITERIA

Randomized controlled trials following the population, intervention, comparison, and outcome (population: pregnant or lactating women; intervention: probiotics; control: placebo or follow-up; outcome: breast milk and infant gut microbiome composition and infant health) principles were included.

METHODS

Using a random effect model, the standard mean difference, risk difference, and risk ratio with 95% confidence interval were used to measure each outcome. All analyses were conducted using the intention-to-treat approach. Heterogeneity was evaluated using I2 statistics.

RESULTS

The final data set included 24 randomized controlled trials with a total of 2761 mothers and 1756 infants. The overall effect of probiotics on the beneficial bacteria detection rate in breast milk had a risk difference of 24% (95% confidence interval, 0.1-0.37; P<.001; I2=91.12%). The pooled mean beneficial and pathogenic bacteria abundance in breast milk had a standard mean difference of 1.22 log10 colony forming units/mL (95% confidence interval, 0.48-1.97; P<.001; I2=95.51%) and -1.05 log10 colony forming unites/mL (95% confidence interval, -1.99 to -0.12; P=.03; I2=96.79%), respectively. The overall abundance of beneficial bacteria in the infant gut had a standard mean difference of 0.89 log10 colony forming units/g (95% confidence interval, 0.22-1.56; P=.01; I2=95.01%). It also controlled infant weight gain (standard mean difference, -0.49 kg/equivalent age; 95% confidence interval, -0.82 to -0.17; P<.001; I2=0.00%) and decreased the occurrence of infantile colic (risk ratio, 0.30; 95% confidence interval, 0.16-0.57; P<.001; I2=0.00%).

CONCLUSION

Maternal probiotic supplements effectively orchestrate the breast milk and infant gut microbiome with a wide range of clinical benefits and safety. Lactobacillus, Bifidobacterium, Streptococcus thermophilus, and S. boulardii can be used as maternal supplements to promote infant health.

The composition of the maternal breastmilk microbiota influences the microbiota network structure during early infancy

BACKGROUND/PURPOSE(S)

Human breastmilk (BM) is important for microbiome maturation in infants across different body sites. Streptococcus and Staphylococcus are considered universally predominant genera in the BM microbiota. However, whether the differential abundance of Streptococcus and Staphylococcus in BM can differentially affect microbiome maturation in infants remains unclear.

METHODS

We recruited exclusively breastfeeding mothers from among the donors of the human milk bank established at National Cheng-Kung University Hospital. The donor mothers provided 35 BM samples at three months (3 M; before introducing children to complementary feeding) and 23 BM samples at six months (6 M; after introducing children to complementary feeding) postpartum. At both time points, samples from different body sites, including nasal swabs, oral swabs and stool, were collected from the mothers and their infants.

RESULTS

Maternal BMI was inversely associated with coagulase-negative Staphylococcus (CoNS) abundance in breastmilk. Staphylococcus caprae representation in BM CoNS showed a negative correlation with Streptococcus abundance. Network analysis revealed that infants fed Staphylococcus-dominated BM had better gut and nasal microbiota networks than infants fed Streptococcus-abundant BM during early infancy.

CONCLUSION

Our work suggests that maternal metabolic status plays a crucial role in Staphylococcus/Streptococcus competition in BM, which in turn can impact the development of the infant microbiota. Our microbiota co-occurrence network analysis might serve as a helpful bioinformatic tool to monitor microbiota maturation during early infancy.

Does the Academy of Breastfeeding Medicine's Clinical Protocol #36 'The Mastitis Spectrum' promote overtreatment and risk worsened outcomes for breastfeeding families? Commentary

BACKGROUND

In 2022 the Academy of Breastfeeding Medicine (ABM) published Clinical Protocol #36: The Mastitis Spectrum, which aims to update clinical approaches to management of benign lactation-related breast inflammation. The protocol has been timely because of the exponential increase in knowledge about the human milk microbiome over the past decade. This Commentary aims to continue respectful debate amongst clinicians and researchers within the Academy of Breastfeeding Medicine and more broadly, confident that we share a fundamental commitment to promote breastfeeding and support the well-being of lactating women, their infants and their families.

ANALYSIS

Although Clinical Protocol #36 offers advances, it does not fulfil the principles of best practice implementation science for translation of evidence into clinical guidelines. Clinical Protocol #36 inaccurately represents studies; misrepresents theoretical models as proven aetiologies; does not consistently attribute sources; does not reliably apply the SORT taxonomy; and relies upon single case reports. As a result, various recommendations in Clinical Protocol #36 lack an evidence-base or credible underlying theoretical model. This includes recommendations to use 'lymphatic drainage' massage, therapeutic ultrasound, and oral lecithin. Similarly, based on a contestable theoretical model which is presented as fact, Clinical Protocol #36 makes the recommendation to either reduce frequency of milk removal or to maintain current frequency of milk removal during an episode of breast inflammation. Although Clinical Protocol #36 limits this advice to cases of 'hyperlactation', the diagnosis 'hyperlactation' itself is undefinable. As a result, this recommendation may put breastfeeding women who present with breast inflammation at risk of worsened inflammation and decreased breast milk production.

CONCLUSION

Clinical Protocol #36 offers some advances in the management of breast inflammation. However, Clinical Protocol #36 also exposes clinicians to two international trends in healthcare which undermine health system sustainability: overdiagnosis, including by over-definition, which increases risk of overtreatment; and antibiotic over-use, which worsens the crisis of global antimicrobial resistance. Clinical Protocol #36 also recommends unnecessary or ineffective interventions which may be accessed by affluent patients within advanced economies but are difficult to access for the global majority. The Academy of Breastfeeding Medicine may benefit from a review of processes for development of Clinical Protocols.

Initial oral microbiota and the impact of delivery mode and feeding practices in 0 to 2 month-old infants

The aim of this study was to describe the initial oral microbiota and how delivery mode and feeding practices impact its diversity in 0-2-month-old infants. This was a cross-sectional study that consisted of one collection of saliva samples from 0-2-month infants at baseline. Ten pairs of mothers and infants were selected. Medical health history, pregnancy, birth, feeding practices (breastfeeding or milk formula), and infant health status was obtained. Pooled microbial samples were obtained from the oral surfaces using a sterile cotton swab. Infants did not receive any breast milk before sampling. After collection, each swab was analyzed through microbiological culture-based procedures, using selective mediums. Cultures were analyzed for the presence of Streptococci, Lactobacillus, Staphylococcus, Enterobacterium , and Candida albicans . Twenty percent of the samples were serially diluted (10-2) to assess the number of bacteria expressed as CFU. Bacillota was the leading phylogenetic group in the infant's pooled microbial sample. The most prevalent genera were Streptococcus, Lactobacillus , and Staphylococcus . Two participants had a positive growth of Candida albicans . The association between genus group, type of delivery, and feeding practices was not statistically significant (p > 0.05). Lactobacillus genus was frequently present in the cesarean delivery group but with slightly higher counts in a vaginal delivery study subject. Exclusively breastfed infants showed presence of Streptococcus, Lactobacillus, Staphylococcus . The oral microbiome in infants (0-2 month-old) is highly heterogeneous and dynamic. Microbiota composition seems to be impacted by mode of delivery, with slight differences among groups. Breastmilk appears as an essential factor in maintaining the oral microbiome's stability and diversity.

Maternal Diet May Modulate Breast Milk Microbiota-A Case Study in a Group of Colombian Women

There is increasing evidence that the diet and nutritional status of women during pregnancy and lactation can modulate the microbiota of their milk and, therefore, the microbiota of the infant. An observational, descriptive, and cross-sectional study was carried out in a group of lactating women. Dietary intake during gestation and the first trimester of lactation was evaluated, and the microbiota was analyzed by 16S ribosomal RNA (rRNA) sequencing using the Illumina platform. Globally, Streptococcus spp. (32%), Staphylococcus spp. (17.3%), Corynebacterium spp. (5.1%) and Veillonella spp. (3.1%) were the predominant bacterial genera. The consumption of simple carbohydrates in gestation (rho = 0.55, p ≤ 0.01) and lactation (rho = 0.50, p ≤ 0.01) were positively correlated with Enterobacter spp. In lactation, a negative correlation was observed between the intake of simple carbohydrates and the genus Bifidobacterium spp. (rho = -0.51 p ≤ 0.01); furthermore, a positive correlation was identified between the intake of folic acid and Akkermansia spp. (rho = 0.47, p ≤ 0.01). Amplicon sequence variants (ASVs) associated with the delivery mode, employment relationship, the baby's gender, birth weight, the Body Mass Index (BMI) of the breastfeeding woman, and gestational weight gain were recovered as covariates in a linear mixed model. The results of this research showed that the maternal nutritional status and diet of women during gestation and lactation could modulate the microbiota of breast milk.

Comparison of bacterial profiles in human milk from mothers of term and preterm infants

BACKGROUND

Reducing the disposal of donated human milk (HM) is important for efficient management of human milk banks (HMBs). The presence of bacteria growth is the main factor that contributes to the disposal of donated HM. The bacterial profile in HM is suspected to differ between term and preterm mothers, with HM from preterm mothers containing more bacteria. Thus, elucidation of the causes of bacterial growth in preterm and term HM may help to reduce the disposal of donated preterm HM. This study compared the bacterial profiles of HM between mothers of term infants and mothers of preterm infants.

METHODS

This pilot study was conducted in the first Japanese HMB, which was initiated in 2017. This study analyzed 214 human milk samples (term: 75, preterm: 139) donated by 47 registered donors (term: 31, preterm: 16) from January to November 2021. Bacterial culture results in term and preterm HM were retrospectively reviewed in May 2022. Differences in total bacterial count and bacterial species count per batch were analyzed using the Mann-Whitney U test. Bacterial loads were analyzed using the Chi-square test or Fisher's exact test.

RESULTS

The disposal rate did not significantly differ between term and preterm groups (p = 0.77), but the total amount of disposal was greater in the preterm group (p < 0.01). Coagulase-negative Staphylococci, Staphylococcus aureus, and Pseudomonas fluorescens were frequently found in both types of HM. Serratia liquefaciens (p < 0.001) and two other bacteria were present in term HM; a total of five types of bacteria, including Enterococcus faecalis and Enterobacter aerogenes (p < 0.001) were present in preterm HM. The median (interquartile range) total bacterial counts were 3,930 (435-23,365) colony-forming units (CFU)/mL for term HM and 26,700 (4,050-334,650) CFU/mL for preterm HM (p < 0.001).

CONCLUSIONS

This study revealed that HM from preterm mothers had a higher total bacterial count and different types of bacteria than HM from term mothers. Additionally, preterm infants can receive nosocomial-infection-causing bacteria in the NICU through their mother's milk. Enhanced hygiene instructions for preterm mothers may reduce the disposal of valuable preterm human milk, along with the risk of HM pathogen transmission to infants in NICUs.

Mechanistic Insights into Immune-Microbiota Interactions and Preventive Role of Probiotics Against Autoimmune Diabetes Mellitus

Recent studies on genetically susceptible individuals and animal models revealed the potential role of the intestinal microbiota in the pathogenesis of type 1 diabetes (T1D) through complex interactions with the immune system. T1D incidence has been increasing exponentially with modern lifestyle altering normal microbiota composition, causing dysbiosis characterized by an imbalance in the gut microbial community. Dysbiosis has been suggested to be a potential contributing factor in T1D. Moreover, several studies have shown the potential role of probiotics in regulating T1D through various mechanisms. Current T1D therapies target curative measures; however, preventive therapeutics are yet to be proven. This review highlights immune microbiota interaction and the immense role of probiotics and postbiotics as important immunological interventions for reducing the risk of T1D.

Impact of the mother's gut microbiota on infant microbiome and brain development

The link between the gut microbiome and health has recently garnered considerable interest in its employment for medicinal purposes. Since the early microbiota exhibits more flexibility compared to that of adults, there is a considerable possibility that altering it will have significant consequences on human development. Like genetics, the human microbiota can be passed from mother to child. This provides information on early microbiota acquisition, future development, and prospective chances for intervention. The succession and acquisition of early-life microbiota, modifications of the maternal microbiota during pregnancy, delivery, and infancy, and new efforts to understand maternal-infant microbiota transmission are discussed in this article. We also examine the shaping of mother-to-infant microbial transmission, and we then explore possible paths for future research to advance our knowledge in this area.

Probiotic Bacteria from Human Milk Can Alleviate Oral Bovine Casein Sensitization in Juvenile Wistar Rats

This study aims to see if probiotic bacteria from human milk could ameliorate oral cow's milk sensitization. The probiotic potential of the SL42 strain isolated from the milk of a healthy young mother was first determined. Rats were then randomly gavaged with cow's milk casein without an adjuvant or assigned to the control group. Each group was further subdivided into three groups, with each receiving only Limosilactobacillus reuteri DSM 17938, SL42, or a phosphate-buffered saline solution. Body weight, temperature, eosinophils, serum milk casein-specific IgE (CAS-IgE), histamine, and serum S100A8/A9 and inflammatory cytokine concentrations were measured. The animals were sacrificed after 59 days; histological sections were prepared, and the spleen or thymus weights, as well as the diversity of the gut microbiota, were measured. On days 1 and 59, SL42 abridged systemic allergic responses to casein by dropping histamine levels (25.7%), CAS-specific IgE levels (53.6%), eosinophil numbers (17%), S100A8/9 (18.7%), and cytokine concentrations (25.4-48.5%). Analyses of histological sections of the jejunum confirmed the protective effect of probiotic bacteria in the CAS-challenged groups. Lactic acid bacteria and Clostridia species were also increased in all probiotic-treated groups. These findings suggest that probiotics derived from human milk could be used to alleviate cow's milk casein allergy.

Regenerative Potential of Human Breast Milk: A Natural Reservoir of Nutrients, Bioactive Components and Stem cells

Human milk is a complex fluid that contains carbohydrates, lipids, proteins, and other bioactive molecules (immunoglobulins, lactoferrin, human milk oligosaccharides, lysozyme, leukocytes, cytokines, hormones, and microbiome) which provide nutritional, immunological, and developmental benefits to the infant. In addition to their involvement in the development, these bioactive compounds have a key role in anti-oncogenicity, neuro-cognitive development, cellular communication, and differentiation. As a result of technological advancements, it has been discovered that human breast milk contains cells that display many of the characteristics of stem cells with multilineage differentiation potentials. Do these cells have any specific properties or roles? Research efforts on breast milk cells have been mainly focused on leukocytes based on their immunological perspective in the early postpartum period. This review summarizes the nutritional components in human milk, i.e., the macro and micronutrients required for the growth and development of infants. Further, it discusses the research work reported concerning the purification, propagation, and differentiation of breast milk progenitor cells and highlights the advancements made in this newly emerging field of stem cell biology and regenerative medicine.

Ecologies, synergies, and biological systems shaping human milk composition-a report from "Breastmilk Ecology: Genesis of Infant Nutrition (BEGIN)" Working Group 2

Human milk is universally recognized as the preferred food for infants during the first 6 mo of life because it provides not only essential and conditionally essential nutrients in necessary amounts but also other biologically active components that are instrumental in protecting, communicating important information to support, and promoting optimal development and growth in infants. Despite decades of research, however, the multifaceted impacts of human milk consumption on infant health are far from understood on a biological or physiological basis. Reasons for this lack of comprehensive knowledge of human milk functions are numerous, including the fact that milk components tend to be studied in isolation, although there is reason to believe that they interact. In addition, milk composition can vary greatly within an individual as well as within and among populations. The objective of this working group within the Breastmilk Ecology: Genesis of Infant Nutrition (BEGIN) Project was to provide an overview of human milk composition, factors impacting its variation, and how its components may function to coordinately nourish, protect, and communicate complex information to the recipient infant. Moreover, we discuss the ways whereby milk components might interact such that the benefits of an intact milk matrix are greater than the sum of its parts. We then apply several examples to illustrate how milk is better thought of as a biological system rather than a more simplistic "mixture" of independent components to synergistically support optimal infant health.

Infant factors that impact the ecology of human milk secretion and composition-a report from "Breastmilk Ecology: Genesis of Infant Nutrition (BEGIN)" Working Group 3

Infants drive many lactation processes and contribute to the changing composition of human milk through multiple mechanisms. This review addresses the major topics of milk removal; chemosensory ecology for the parent-infant dyad; the infant's inputs into the composition of the human milk microbiome; and the impact of disruptions in gestation on the ecology of fetal and infant phenotypes, milk composition, and lactation. Milk removal, which is essential for adequate infant intake and continued milk synthesis through multiple hormonal and autocrine/paracrine mechanisms, should be effective, efficient, and comfortable for both the lactating parent and the infant. All 3 components should be included in the evaluation of milk removal. Breastmilk "bridges" flavor experiences in utero with postweaning foods, and the flavors become familiar and preferred. Infants can detect flavor changes in human milk resulting from parental lifestyle choices, including recreational drug use, and early experiences with the sensory properties of these recreational drugs impact subsequent behavioral responses. Interactions between the infant's own developing microbiome, that of the milk, and the multiple environmental factors that are drivers-both modifiable and nonmodifiable-in the microbial ecology of human milk are explored. Disruptions in gestation, especially preterm birth and fetal growth restriction or excess, impact the milk composition and lactation processes such as the timing of secretory activation, adequacy of milk volume and milk removal, and duration of lactation. Research gaps are identified in each of these areas. To assure a sustained and robust breastfeeding ecology, these myriad infant inputs must be systematically considered.

Improvement and Validation of a Genomic DNA Extraction Method for Human Breastmilk

The human milk microbiota (HMM) of healthy women can vary substantially, as demonstrated by recent advances in DNA sequencing technology. However, the method used to extract genomic DNA (gDNA) from these samples may impact the observed variations and potentially bias the microbiological reconstruction. Therefore, it is important to use a DNA extraction method that is able to effectively isolate gDNA from a diverse range of microorganisms. In this study, we improved and compared a DNA extraction method for gDNA isolation from human milk (HM) samples to commercial and standard protocols. We evaluated the extracted gDNA using spectrophotometric measurements, gel electrophoresis, and PCR amplifications to assess its quantity, quality, and amplifiability. Additionally, we tested the improved method’s ability to isolate amplifiable gDNA from fungi, Gram-positive and Gram-negative bacteria to validate its potential for reconstructing microbiological profiles. The improved DNA extraction method resulted in a higher quality and quantity of the extracted gDNA compared to the commercial and standard protocols and allowed for polymerase chain reaction (PCR) amplification of the V3–V4 regions of the 16S ribosomal gene in all the samples and the ITS-1 region of the fungal 18S ribosomal gene in 95% of the samples. These results suggest that the improved DNA extraction method demonstrates better performance for gDNA extraction from complex samples such as HM.

Domestication and microbiome succession may drive pathogen spillover

Emerging infectious diseases have posed growing medical, social and economic threats to humanity. The biological background of pathogen spillover or host switch, however, still has to be clarified. Disease ecology finds pathogen spillovers frequently but struggles to explain at the molecular level. Contrarily, molecular biological traits of host-pathogen relationships with specific molecular binding mechanisms predict few spillovers. Here we aim to provide a synthetic explanation by arguing that domestication, horizontal gene transfer even between superkingdoms as well as gradual exchange of microbiome (microbiome succession) are essential in the whole scenario. We present a new perspective at the molecular level which can explain the observations of frequent pathogen spillover events at the ecological level. This proposed rationale is described in detail, along with supporting evidence from the peer-reviewed literature and suggestions for testing hypothesis validity. We also highlight the importance of systematic monitoring of virulence genes across taxonomical categories and in the whole biosphere as it helps prevent future epidemics and pandemics. We conclude that that the processes of domestication, horizontal gene transfer and microbial succession might be important mechanisms behind the many spillover events driven and accelerated by climate change, biodiversity loss and globalization.

Effects of soybean hulls and corn stalk on the performance, colostrum composition and faecal microflora of pregnant sows

This study was conducted to investigate the effects of different supplementation levels of soybean hulls and corn stalk in high-fibre gestation diet on the performance, colostrum composition and faecal microbiota of sows. Forty first-farrowing Danish Landrace sows were randomly assigned to five dietary treatment groups. The control (CON, 3.15% crude fibre) group was fed a normal diet, and the treatment groups were soybean hulls low-fibre (SHL, 6.00% crude fibre) group, soybean hulls high-fibre (SHH, 8.00% crude fibre) group, corn stalk low-fibre (CSL, 6.00% crude fibre) group and corn stalk high-fibre (CSH, 8.00% crude fibre) group. The weaning weight of the litter and the average daily feed intake of the lactating sows in the SHL, SHH and CSH groups were higher than those in the CON group (p < 0.05). The immunoglobulin A and G levels of the colostrum in the SHL, SHH, CSL and CSH groups were higher than those in the CON group (p < 0.05), and the immunoglobulin M levels in the SHL, SHH and CSH groups were higher than those in the CON group (p < 0.05). The abundance of Proteobacteria at the phylum level in the CON group was higher than that in the CSL, CSH and SHH groups (p < 0.05). The abundance of Lactobacillaceae at the family level in the SHH and CSL groups were higher than that in the CON group (p < 0.05). The abundance of Lactobacillus at the genus level in the SHH and CSL groups were higher than that in the CON group (p < 0.05). In conclusion, SHH group had the best effect, and the optimal crude fibre level in the gestation diet of sows is 8%.

The breast milk and childhood gastrointestinal microbiotas and disease outcomes: a longitudinal study

BACKGROUND

We aimed to characterize breast milk microbiota and define associations with saliva and fecal microbiota and selected diseases in preschool children.

METHODS

In a longitudinal cohort study, the microbiotas from breast milk, mouth, and fecal samples were characterized by 16S rRNA gene sequencing. Questionnaires and medical records provided information on demographics, medical, and dental data.

RESULTS

The phylogeny in breast milk, saliva swabs, and feces differed at all levels (p < 0.0003), though all harbored species in Streptococcus, Veillonella, and Haemophilus. Species richness was highest in breast milk with increasing resemblance with the oral swab microbiota by increasing age. Caries-affected children at age 5 had been fed breast milk with tenfold higher abundance of caries-associated bacteria, e.g., Streptococcus mutans, than caries-free children (p < 0.002). At that age, taxa, e.g., Neisseria sicca were overrepresented in saliva swabs of children with otitis media (LDA score >2, p < 0.05). Gut symbionts, e.g., Bacteroides, were underrepresented in 3-month fecal samples in children later diagnosed with allergic disease (LDA score >2, p < 0.05).

CONCLUSIONS

Distinct microbiotas for the three sources were confirmed, though resemblance between milk and oral swab microbiota increased by age. Future studies should evaluate if the observed associations with disease outcomes are causal.

IMPACT

Few studies have studied the association between breast milk microbiota and gastrointestinal microbiota beyond early infancy. The present study confirms distinct microbiota profiles in breast milk, saliva swabs, and feces in infancy and indicates increasing resemblance between breast milk and the oral microbiota by increasing age. The fecal microbiota at 3 months was associated with later allergic disease; the saliva microbiota by age 5 differed between children with and without otitis media at the same age; and children with caries by age 5 had been fed breast milk with a higher abundance of caries-associated bacteria.

Effects of yeast-derived postbiotic supplementation in late gestation and lactation diets on performance, milk quality, and immune function in lactating sows

This experiment was conducted to determine the effects of yeast-derived postbiotic (YDP) supplementation in sow diets during late gestation and lactation on the performance of sows and their offspring. At 90-d gestation, 150 sows (Landrace × Large White, parity: 3.93 ± 0.11) were allocated to three dietary treatments (n = 50 per treatment): 1) basal diet (control [CON]), 2) basal diet with 1.25 g/kg YDP (0.125 group), and 3) basal diet with 2.00 g/kg YDP (0.200 group). The experiment continued until the end of weaning (day 21 of lactation). Supplementation with YDP resulted in greater deposition of backfat in sows during late gestation and an increasing trend in average weaning weight of piglets than observed in the CON group (P < 0.01, P = 0.05). Supplementation with YDP decreased piglet mortality and diarrhea index in piglets (P < 0.05). In farrowing sows' serum, the glutathione peroxide content in the YDP group was lower than that in the CON group (P < 0.05); the content of immunoglobulin A (IgA) in the 0.200 group or YDP group was higher than that in the CON group (P < 0.05). In lactating sows' serum, malondialdehyde content was higher in the YDP group (P < 0.05). In day 3 milk of sows, the 0.200 group tended to increase the lactose content (P = 0.07), and tended to decrease the secretory immunoglobulin A (sIgA) content (P = 0.06) with respect to that in the CON group. The sIgA content in the YDP group was lower than that in the CON group (P < 0.05). In the milk of sows, the 0.200 group tended to increase the lactose content with respect to that in the CON group (P = 0.08); the immunoglobulin G (IgG) content in the 0.125 group or YDP group was higher than that in the CON group (P < 0.05). YDP supplementation increased the IgA content in the milk (P < 0.01). In sow placenta, the content of total anti-oxidant capacity in the YDP group was higher than that in the CON group (P = 0.05); and the content of transforming growth factor-β in the YDP group was higher than that in the CON group (P < 0.05). In piglet serum, the content of IgG and immunoglobulin M in the 0.125 group was higher than that in the CON and 0.200 groups (P < 0.05). In summary, this study indicated that feeding sows diets supplemented with YDP from late gestation through lactation increased sows' backfat deposition in late gestation and piglets' weaning weight; decreased piglet mortality and diarrhea index in piglets; and improved maternal and offspring immunity.

Breast Milk-Derived Limosilactobacillus reuteri Prevents Atopic Dermatitis in Mice via Activating Retinol Absorption and Metabolism in Peyer's Patches

SCOPE

Supplementing Limosilactobacillus reuteri Fn041, a breast milk-derived probiotic from agricultural and pastoral areas, to maternal mice during late pregnancy and lactation prevents atopic dermatitis (AD) in offspring. This study aims to elucidate the molecular mechanism of Fn041-mediated immune regulation.

METHODS AND RESULTS

Fn041 is administered prenatal and postnatal to maternal mice, and to offspring after weaning. The ears are administered with calcipotriol to induce AD. Fn041 treatment significantly alleviates ear inflammation, and reduces mast cell infiltration. Fn041 treatment upregulates and downregulates intestinal ZO-1 and Claudin-2 mRNA expression, respectively. Transcriptome analysis of Peyer's patches reveals that pathways related to DNA damage repair are activated in AD mice, which is inhibited by Fn041 treatment. Fn041 activates pathways related to retinol absorption and metabolism. Untargeted metabolomic analysis reveals that Fn041 treatment increases plasma retinol and kynurenine. Fn041 treatment does not significantly alter the overall cecal microbiota profile, only increases the relative abundances of Ligilactobacillus apodemi, Ligilactobacillus murinus, Akkermansia muciniphila, and Bacteroides thetaiotaomicron.

CONCLUSIONS

Fn041 induces anti-AD immune responses directly by promoting the absorption and metabolism of retinol in Peyer's patches, and plays an indirect role by strengthening the mucosal barrier and increasing the abundance of specific anti-AD bacteria in the cecum.

Sterilization efficacy of a new water-free breast milk pasteurizer

BACKGROUND

Breast milk, nature's optimum source of nutrition for infants, can contain undesirable microorganisms that cause severe morbidity. After an outbreak of multidrug-resistant Escherichia coli among neonates receiving breast milk donated by another mother in our neonatal intensive care unit (NICU), we were motivated to develop a high-grade breast milk pasteurizer (BMP) designed to thaw and pasteurize breast milk at 63°C for 30 min in a sealed bag without having to open the bag or immerse it in water.

METHODS

Pre-existing bacteria and spiked cytomegalovirus (CMV) were measured pre- and post-pasteurization in frozen breast milk donated by mothers of children admitted to the NICU.

RESULTS

Among 48 breast milk samples (mean ± standard deviation [SD]), pre-existing bacterial counts of 5.1±1.1 × 104 colony forming units (cfu)/mL decreased to less than 10 cfu/mL (below detection level) in 45 samples after pasteurization for 30 min. In three samples, 10-110 cfu/mL persisted. As no CMV was detected in any of the 48 samples, CMV at ≥5 × 104 pfu/mL was spiked into 11 breast milk samples. After just 10 min of pasteurization, infectious CMV was not detected (threshold <50 pfu/mL) in any sample.

CONCLUSION

A new BMP was shown to pasteurize milk effectively with more than a 3-log reduction of microorganisms. Compared to conventional pasteurizers, this device reduces the effort involved in pasteurizing breast milk, avoids various contamination risks, and may reduce the risk of infectious disease transmission via breast milk.

Human Milk from Tandem Feeding Dyads Does Not Differ in Metabolite and Metataxonomic Features When Compared to Single Nursling Dyads under Six Months of Age

Given the long-term advantages of exclusive breastfeeding to infants and their mothers, there is both an individual and public health benefit to its promotion and support. Data on the composition of human milk over the course of a full period of lactation for a single nursling is sparse, but data on human milk composition during tandem feeding (feeding children of different ages from different pregnancies) is almost entirely absent. This leaves an important knowledge gap that potentially endangers the ability of parents to make a fully informed choice on infant feeding. We compared the metataxonomic and metabolite fingerprints of human milk samples from 15 tandem feeding dyads to that collected from ten exclusively breastfeeding single nursling dyads where the nursling is under six months of age. Uniquely, our cohort also included three tandem feeding nursling dyads where each child showed a preferential side for feeding-allowing a direct comparison between human milk compositions for different aged nurslings. Across our analysis of volume, total fat, estimation of total microbial load, metabolite fingerprinting, and metataxonomics, we showed no statistically significant differences between tandem feeding and single nursling dyads. This included comparisons of preferential side nurslings of different ages. Together, our findings support the practice of tandem feeding of nurslings, even when feeding an infant under six months.

Mother-infant transmission of human microbiota

Humans are colonised by a highly adapted microbiota with coevolved functions that promote human health, development and disease resistance. Acquisition and assembly of the microbiota start at birth and recent evidence suggests that it coincides with, and informs, immune system development and regulation in the rapidly growing infant. Several large-scale studies have identified Bifidobacterium and Bacteroides species maternally transmitted to infants, many of which are capable of colonising over the longer term. Disruption of maternal transmission by caesarean section and antibiotic exposure around birth is associated with a higher incidence of pathogen colonisation and immune-related disorders in children. In this review, we discuss key maternally transmitted bacterial species, their sources and their potential role in shaping immune development. Maternal transmission of gut bacteria provides a microbial 'starter kit' for infants which promotes healthy growth and disease resistance. Optimising and nurturing this under-appreciated form of kinship should be considered as a priority.

Milk microbiomes of three great ape species vary among host species and over time

In mammalian neonates, milk consumption provides nutrients, growth factors, immune molecules, and microbes. Milk microbiomes are increasingly recognized for their roles in seeding infant gut microbiomes and priming immune development. However, milk microbiome variation within and among individuals remains under investigation. We used 16S rRNA gene sequencing to investigate factors shaping milk microbiomes in three captive great ape species: Gorilla gorilla gorilla (individuals, N = 4; samples, n = 29), Pongo abelii (N = 2; n = 16), and Pongo pygmaeus (N = 1; n = 9). We demonstrate variation among host species, over lactation, and between housing facilities. In phylogenetic community composition, milk microbiomes were distinct among the three ape species. We found only a few shared, abundant bacterial taxa and suggest that they likely serve functional roles. The diversity and community composition of milk microbiomes showed gradual changes over time in gorillas and the Bornean orangutan, which was detectable with our comprehensive sampling over lactation stages (> 300-day span). In gorillas, milk microbiomes differed between housing facilities, but were similar between dams within a facility. These results support the strong influence of evolutionary history in shaping milk microbiomes, but also indicate that more proximate cues from mother, offspring, and the environment affect the distribution of rarer microbial taxa.

A Pilot Study on Donor Human Milk Microbiota: A Comparison with Preterm Human Milk Microbiota and the Effect of Pasteurization

Human milk (HM) is the best feeding option for preterm infants; however, when mother's own milk (MOM) is not available, pasteurized donor human milk (DHM) is the best alternative. In this study, we profiled DHM microbiota (19 samples) using 16S rRNA amplicon sequencing and compared its compositional features with the MOM microbiota (14 samples) from mothers who delivered prematurely (PT-MOM). As a secondary study aim, we assessed the specific effect of pasteurization on the characteristics of the DHM microbiota. DHM showed significantly higher alpha diversity and significant segregation from PT-MOM. Compositionally, the PT-MOM microbiota had a significantly higher proportion of Staphylococcus than DHM, with Streptococcus tending to be and Pseudomonas being significantly overrepresented in DHM compared with the PT-MOM samples. Furthermore, pasteurization affected the HM microbiota structure, with a trend towards greater biodiversity and some compositional differences following pasteurization. This pilot study provided further evidence on the HM microbial ecosystem, demonstrating that the DHM microbiota differs from the PT-MOM microbiota, possibly due to inherent differences between HM donors and mothers delivering prematurely, and that pasteurization per se impacts the HM microbiota. Knowledge about HM microbiota needs to be acquired by investigating the effect of DHM processing to develop strategies aimed at improving DHM quality while guaranteeing its microbiological safety.

Human milk microbiota: what did we learn in the last 20 years?

Human milk (HM) is the gold standard for infant nutrition during the first months of life. Beyond its nutritional components, its complex bioactive composition includes microorganisms, their metabolites, and oligosaccharides, which also contribute to gut colonization and immune system maturation. There is growing evidence of the beneficial effects of bacteria present in HM. However, current research presents limited data on the presence and functions of other organisms. The potential biological impacts on maternal and infant health outcomes, the factors contributing to milk microbes' variations, and the potential functions in the infant's gut remain unclear. This review provides a global overview of milk microbiota, what the actual knowledge is, and what the gaps and challenges are for the next years.

Secretory IgA: Linking microbes, maternal health, and infant health through human milk

Secretory immunoglobulin A (SIgA) in human milk plays a central role in complex maternal-infant interactions that influence long-term health outcomes. Governed by genetics and maternal microbial exposure, human milk SIgA shapes both the microbiota and immune system of infants. Historically, SIgA-microbe interactions have been challenging to unravel due to their dynamic and personalized nature, particularly during early life. Recent advances have helped to clarify how SIgA acts beyond simple pathogen clearance to help guide and constrain a healthy microbiota, promote tolerance, and influence immune system development. In this review, we highlight these new findings in the context of the critical early-life window and propose outstanding areas of study that will be key to harnessing the benefits of SIgA to support healthy immune development during infancy.