Human milk: mother nature's prototypical probiotic food?

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

This review explores the role of microorganisms and metabolites in human breast milk and their impact on neonatal health. Breast milk serves as both a primary source of nutrition for newborns and contributes to the development and maturation of the digestive, immunological, and neurological systems. It has the potential to reduce the risks of infections, allergies, and asthma. As our understanding of the properties of human milk advances, there is growing interest in incorporating its benefits into personalized infant nutrition strategies, particularly in situations in which breastfeeding is not an option. Future infant formula products are expected to emulate the composition and advantages of human milk, aligning with an evolving understanding of infant nutrition. The long-term health implications of human milk are still under investigation.

Human Milk Microbiome-A Review of Scientific Reports

One of the most important bioactive components of breast milk are free breast milk oligosaccharides, which are a source of energy for commensal intestinal microorganisms, stimulating the growth of Bifidobacterium, Lactobacillus, and Bacteroides in a child's digestive tract. There is some evidence that maternal, perinatal, and environmental-cultural factors influence the modulation of the breast milk microbiome. This review summarizes research that has examined the composition of the breast milk microbiome and the factors that may influence it. The manuscript highlights the potential importance of the breast milk microbiome for the future development and health of children. The origin of bacteria in breast milk is thought to include the mother's digestive tract (entero-mammary tract), bacterial exposure to the breast during breastfeeding, and the retrograde flow of breast milk from the infant's mouth to the woman's milk ducts. Unfortunately, despite increasingly more precise methods for assessing microorganisms in human milk, the topic of the human milk microbiome is still quite limited and requires scientific research that takes into account various conditions.

From gut to skin: exploring the potential of natural products targeting microorganisms for atopic dermatitis treatment

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease. Recent studies have revealed that interactions between pathogenic microorganisms, which have a tendency to parasitize the skin of AD patients, play a significant role in the progression of the disease. Furthermore, specific species of commensal bacteria in the human intestinal tract can have a profound impact on the immune system by promoting inflammation and pruritogenesis in AD, while also regulating adaptive immunity. Natural products (NPs) have emerged as promising agents for the treatment of various diseases. Consequently, there is growing interest in utilizing natural products as a novel therapeutic approach for managing AD, with a focus on modulating both skin and gut microbiota. In this review, we discuss the mechanisms and interplay between the skin and gut microbiota in relation to AD. Additionally, we provide a comprehensive overview of recent clinical and fundamental research on NPs targeting the skin and gut microbiota for AD treatment. We anticipate that our work will contribute to the future development of NPs and facilitate research on microbial mechanisms, based on the efficacy of NPs in treating AD.

Antibiotics and Probiotics for Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a disorder of a gut-brain interaction characterised by abdominal pain and a change in stool form or frequency. Current symptom-based definitions and the classification of IBS promote heterogeneity amongst patients, meaning that there may be several different pathophysiological abnormalities leading to similar symptoms. Although our understanding of IBS is incomplete, there are several indicators that the microbiome may be involved in a subset of patients. Techniques including a faecal sample analysis, colonic biopsies, duodenal aspirates or surrogate markers, such as breath testing, have been used to examine the gut microbiota in individuals with IBS. Because of a lack of a clear definition of what constitutes a healthy gut microbiota, and the fact that alterations in gut microbiota have only been shown to be associated with IBS, a causal relationship is yet to be established. We discuss several hypotheses as to how dysbiosis may be responsible for IBS symptoms, as well as potential treatment strategies. We review the current evidence for the use of antibiotics and probiotics to alter the microbiome in an attempt to improve IBS symptoms. Rifaximin, a non-absorbable antibiotic, is the most studied antibiotic and has now been licensed for use in IBS with diarrhoea in the USA, but the drug remains unavailable in many countries for this indication. Current evidence also suggests that certain probiotics, including Lactobacillus plantarum DSM 9843 and Bifidobacterium bifidum MIMBb75, may be efficacious in some patients with IBS. Finally, we describe the future challenges facing us in our attempt to modulate the microbiome to treat IBS.

Human milk microbial species are associated with infant head-circumference during early and late lactation in Guatemalan mother-infant dyads

Human milk contains abundant commensal bacteria that colonize and establish the infant's gut microbiome but the association between the milk microbiome and head circumference during infancy has not been explored. For this cross-sectional study, head-circumference-for-age-z-scores (HCAZ) of vaginally delivered breastfed infants were collected from 62 unrelated Mam-Mayan mothers living in eight remote rural communities in the Western Highlands of Guatemala during two stages of lactation, 'early' (6-46 days postpartum, n = 29) or 'late' (109-184 days postpartum, n = 33). At each stage of lactation, infants were divided into HCAZ ≥ -1 SD (early: n = 18; late: n = 14) and HCAZ < -1 SD (early: n = 11; late: n = 19). Milk microbiome communities were assessed using 16S ribosomal RNA gene sequencing and DESeq2 was used to compare the differential abundance (DA) of human milk microbiota with infant HCAZ subgroups at both stages of lactations. A total of 503 ESVs annotated 256 putative species across the 64 human milk samples. Alpha-diversity using Chao index uncovered a difference in microbial community richness between HCAZ ≥ -1 SD and HCAZ < -1 SD groups at late lactation (p = 0.045) but not at early lactation. In contrast, Canonical Analysis of Principal Coordinates identified significant differences between HCAZ ≥ -1 SD and HCAZ < -1 SD at both stages of lactation (p = 0.003); moreover, 26 milk microbial taxa differed in relative abundance (FDR < 0.05) between HCAZ ≥ -1 SD and HCAZ < -1 SD, with 13 differentially abundant at each lactation stage. Most species in the HCAZ ≥ -1 SD group were Streptococcus species from the Firmicutes phylum which are considered human colonizers associated with human milk whereas the HCAZ < -1 SD group at late lactation had more differentially abundant taxa associated with environmentally and 'potentially opportunistic' species belonging to the Actinobacteria genus. These findings suggest possible associations between brain growth of breastfed infants and the milk microbiome during lactation. Importantly, these data provide the first evidence of cross talk between the human milk microbiome and the infant brain that requires further investigation.

Microbial Interrelationships across Sites of Breastfeeding Mothers and Infants at 6 Weeks Postpartum

Infancy is a critical life stage for the establishment of the gut microbiome. Human milk contains a unique microbial ecosystem that serves as a continuous source of commensal bacteria for the infant. However, the origin of the human milk microbiota, how it is influenced by breastfeeding exclusivity, and its role in infant gut microbiota assembly are not clear. To interrogate these questions, we examined the relationships among fecal, oral, breast skin, and human milk microbiota of 33 exclusively breastfeeding (EBF) and mixed-feeding (MF; human milk + infant formula) mother–infant pairs at 6 weeks postpartum. Here, we show that MF infants have a significantly more diverse oral microbiome comprised of lower relative abundances of Streptococcus and Gemella and higher abundances of Veillonella. Using both SourceTracker2 and FEAST, we demonstrate breast skin and infant saliva as the principal contributing sources to the human milk microbiota. Of the sampled sites, human milk and maternal stool were predicted to contribute the largest fraction to the infant fecal microbiome, but the majority of the community was estimated to arise from unknown sources. Lastly, we identified twenty-one significant co-occurrence relationships between bacteria in human milk and on other maternal and infant body sites. These results demonstrate several unique microbial interrelationships between breastfeeding dyads, providing insight into potential mechanisms of microbial assembly in early life.

Breast Milk: A Meal Worth Having

A mother is gifted with breast milk, the natural source of nutrition for her infant. In addition to the wealth of macro and micro-nutrients, human milk also contains many microorganisms, few of which originate from the mother, while others are acquired from the mouth of the infant and the surroundings. Among these microbes, the most commonly residing bacteria are Staphylococci, Streptococci, Lactobacilli and Bifidobacteria. These microorganisms initiate and help the development of the milk microbiota as well as the microbiota of the gastrointestinal tract in infants, and contribute to developing immune regulatory factors such as cytokines, growth factors, lactoferrin among others. These factors play an important role in reducing the risk of developing chronic diseases like type 2 diabetes, asthma and others later in life. In this review, we will summarize the known benefits of breastfeeding and highlight the role of the breast milk microbiota and its cross-talk with the immune system in breastfed babies during the early years of life.

The Impact of Probiotics, Prebiotics, and Synbiotics during Pregnancy or Lactation on the Intestinal Microbiota of Children Born by Cesarean Section: A Systematic Review

The gut microbiota is a key factor in the correct development of the gastrointestinal immune system. Studies have found differences between the gut microbiota of newborns delivered by cesarean section compared to those vaginally delivered. Our objective was to evaluate the effect of ingestion of probiotics, prebiotics, or synbiotics during pregnancy and/or lactation on the development of the gut microbiota of the C-section newborns. We selected experimental studies in online databases from their inception to October 2021. Of the 83 records screened, 12 met the inclusion criteria. The probiotics used belonged to the genera Lactobacillus, Bifidobacterium, Propionibacterium, and Streptococcus, or a combination of those, with dosages varying between 2 × 10⁶ and 9 × 10¹¹ CFU per day, and were consumed during pregnancy and/or lactation. Probiotic strains were combined with galacto-oligosaccharides, fructo-oligosaccharides, or bovine milk-derived oligosaccharides in the synbiotic formulas. Probiotic, prebiotic, and synbiotic interventions led to beneficial gut microbiota in cesarean-delivered newborns, closer to that in vaginally delivered newborns, especially regarding Bifidobacterium colonization. This effect was more evident in breastfed infants. The studies indicate that this beneficial effect is achieved when the interventions begin soon after birth, especially the restoration of bifidobacterial population. Changes in the infant microbial ecosystem due to the interventions seem to continue after the end of the intervention in most of the studies. More interventional studies are needed to elucidate the optimal synbiotic combinations and the most effective strains and doses for achieving the optimal gut microbiota colonization of C-section newborns.

Probiotics in the treatment of Helicobacter pylori infection: reality and perspective

Helicobacter pylori (H. pylori) infection is one of the most common in the world today, associated with the development of acute or chronic inflammatory diseases of the gastroduodenal tract. In order to eradicate the pathogen, various antibacterial therapy regimens have been proposed, based on the use of several chemotherapeutic drugs and a proton pump inhibitor (PPI). However, recent studies indicate a decrease in antibiotic effectiveness due to both the growth rate of H. pylori resistance and side effects, often due to the development of dysbiosis. One of the promising areas of investigation is the treatment with probiotic therapy of helicobacteriosis. The use of probiotics, in the context of H. pylori infection, has two main reasons. The first is related to the use of certain probiotics to reduce the frequency of undesirable gastrointestinal consequences during H. pylori eradication therapy. The second is associated with the antagonistic effect of individual probiotics on H. pylori and the potentiation of the eradication effect. The purpose of this review was to summarize the latest data on the use of probiotics to enhance H. pylori eradication and to restore the gastrointestinal microbiota. Many unresolved questions, about the choice of the specific composition of the probiotic cocktail, dosage, duration of therapy, mechanisms of the antimicrobial action of probiotics, as well as possible negative consequences of such therapy, remain.

The hidden universe of human milk microbiome: origin, composition, determinants, role, and future perspectives

Although traditionally considered sterile, human milk is currently recognized as an alive ecosystem that harbors not only bacteria, but also viruses, fungi and yeasts, and minor genera, collectively known as the human milk microbiome (HMM). The seeding of HMM is a complex phenomenon whose dynamics are still a matter of research. Many factors contribute to its determination, both maternal, neonatal, environmental, and related to human milk itself. The transmission of microorganisms to the infant through breastfeeding may impact its present and future health, mainly shaping the GI tract microbiome and immune system. The existence and persistence of HMM as a conserved feature among different species may also have an evolutionary meaning, which will become apparent only in evolutionary times.

CONCLUSION

The complexities of HMM warrant further research in order to deepen our knowledge on its origin, determinants, and impact on infants' health. The practical and translational implications of research on HMM (e.g., reconstitution of donor human milk through inoculation of infant's own mother milk, modulation of HMM through maternal dietary supplementation) should not be overlooked.

WHAT IS KNOWN

• Human milk harbors a wide variety of microorganisms, ranging from bacteria to viruses, fungi and yeasts, and minor genera. • Human milk microbiome is shaped over time by many factors: maternal, neonatal, environmental, and related to human milk itself. • The transmission of microorganisms through breastfeeding may impact the infant's present and future health.

WHAT IS NEW

• We provide an overview on human milk microbiome, hopefully encouraging physicians to consider it among the other better-known breastfeeding benefits. • Further studies, with standardized and rigorous study designs to enhance accuracy and reproducibility of the results, are needed to deepen our knowledge of the human milk microbiota and its role in newborn and infant's health.

Human milk microbiome: From actual knowledge to future perspective

Human milk is the gold standard for infant nutrition during the first months of life since it is perfectly adapted to the neonatal nutritional requirements and supports infant growth and development. Human milk contains a complex nutritional and bioactive composition including microorganisms and oligosaccharides which would also contribute to the gut and immune system maturation. Despite the growing evidence, the factors contributing to milk microbes' variations and the potential functions on the infant's gut are still uncovered. This short-review provides a general overview of milk microbiota, potential factors shaping its composition, contribution to the infant microbiota and immune system development, including the suggested biological relevance for infant health as well as the description of tools and strategies aimed to restore and module microbes in milk.

Gold standard for nutrition: a review of human milk oligosaccharide and its effects on infant gut microbiota

Human milk is the gold standard for nutrition of infant growth, whose nutritional value is mainly attributed to human milk oligosaccharides (HMOs). HMOs, the third most abundant component of human milk after lactose and lipids, are complex sugars with unique structural diversity which are indigestible by the infant. Acting as prebiotics, multiple beneficial functions of HMO are believed to be exerted through interactions with the gut microbiota either directly or indirectly, such as supporting beneficial bacteria growth, anti-pathogenic effects, and modulation of intestinal epithelial cell response. Recent studies have highlighted that HMOs can boost infants health and reduce disease risk, revealing potential of HMOs in food additive and therapeutics. The present paper discusses recent research in respect to the impact of HMO on the infant gut microbiome, with emphasis on the molecular basis of mechanism underlying beneficial effects of HMOs.

Analysis of clinical outcomes of oropharyngeal colostrum administration in very low-birth-weight preterm newborns

OBJECTIVES

Colostrum is the first secretion produced by the mammary glands and is present through the seventh day after birth. Colostrum has important immunomodulatory components and protective factors that contribute to the protection and development of newborns. The oropharyngeal administration of colostrum (OAC) has been proposed as a potential nutritional option for very low-birth-weight (VLBW) newborns (<1500 g). This study aimed to analyze the clinical outcomes of VLBW infants receiving OAC.

METHODS

This is a retrospective longitudinal study with nonprobability sampling of VLBW infants on the OAC protocol. VLBW infants for whom no OAC data were available, who received no dose, or who died within the first 7 d of life were excluded. The Mann-Whitney test was used to compare quantitative variables and the Wilcoxon test to assess the evolution of anthropometric values with a significance level of 5% (P < 0.05).

RESULTS

Enteral nutritional therapy was commenced after 1 d (median: 1 d; interquartile range [IQR], 1-1 d). Full enteral feeding was achieved after 11 d (median: 11.0 d; IQR, 9.0-16.0 d). Birth weight was recovered after 11 d (median: 11 d; IQR, 7.0-14.0 d). OAC was commenced at 3 d of life, and 32.5 doses (IQR, 21.0-44.0 d) were given in total. There were significant differences in the evolution of anthropometric characteristics during hospitalization, with a tendency to recover birth weight more quickly the higher the number of doses administered (P = 0.07). Time to full enteral feeding was significantly longer and time to recovery of birth weight significantly shorter when OAC was commenced ≤3 d after birth (P = 0.023).

CONCLUSIONS

OAC was associated with a shorter time to recover birth weight and time to full enteral feeding.

Infant Feeding Alters the Longitudinal Impact of Birth Mode on the Development of the Gut Microbiota in the First Year of Life

Cesarean-delivered (CD) infants harbor a distinct gut microbiome from vaginally delivered (VD) infants, however, during infancy, the most important driver of infant gut microbial colonization is infant feeding. Earlier studies have shown that breastfeeding is associated with higher levels of health-promoting bacteria such and Bifidobacterium and Bacteroides via modulation of the immune system, and production of metabolites. As the infant gut matures and solid foods are introduced, it is unclear whether longer duration of breast feeding restore loss of beneficial taxa within the intestinal microbiota of operatively delivered infants. Within the New Hampshire Birth Cohort Study, we evaluated the longitudinal effect of delivery mode and infant feeding on the taxonomic composition and functional capacity of developing gut microbiota in the First year of life. Microbiota of 500 stool samples collected between 6 weeks and 12 months of age (from 229 infants) were characterized by 16S ribosomal RNA sequencing. Shotgun metagenomic sequencing was also performed on 350 samples collected at either 6 weeks or 12 months of age. Among infant participants, 28% were cesarean-delivered (CD) infants and most (95%) initiated breastfeeding within the first six months of life, with 26% exclusively breastfed and 69% mixed-fed (breast milk and formula), in addition to complementary foods by age 1. Alpha (within-sample) diversity was significantly lower in CD infants compared to vaginally delivered (VD) infants (P < 0.05) throughout the study period. Bacterial community composition clustering by both delivery mode and feeding duration at 1 year of age revealed that CD infants who were breast fed for < 6 months were more dissimilar to VD infants than CD infants who breast fed for ≥ 6 months. We observed that breastfeeding modified the longitudinal impact of delivery mode on the taxonomic composition of the microbiota by 1 year of age, with an observed increase in abundance of Bacteroides fragilis and Lactobacillus with longer duration of breastfeeding among CD infants while there was an increase in Faecalibacterium for VD infants. Our findings confirm that duration of breastfeeding plays a critical role in restoring a health-promoting microbiome, call for further investigations regarding the association between breast milk exposure and health outcomes in early life.

Human Milk Microbiota in an Indigenous Population Is Associated with Maternal Factors, Stage of Lactation, and Breastfeeding Practices

BACKGROUND

Human milk contains a diverse community of bacteria that are modified by maternal factors, but whether these or other factors are similar in developing countries has not been explored. Our objective was to determine whether the milk microbiota was modified by maternal age, BMI, parity, lactation stage, subclinical mastitis (SCM), and breastfeeding practices in the first 6 mo of lactation in an indigenous population from Guatemala.

METHODS

For this cross-sectional study, Mam-Mayan indigenous mothers nursing infants aged <6 mo were recruited. Unilateral human milk samples were collected (n = 86) and processed for 16S rRNA sequencing at the genus level. Microbial diversity and relative abundance were compared with maternal factors [age, BMI, parity, stage of lactation, SCM, and 3 breastfeeding practices (exclusive, predominant, mixed)] obtained through questionnaires.

RESULTS

Streptococcus was the most abundant genus (33.8%), followed by Pseudomonas (18.7%) and Sphingobium (10.7%) but relative abundance was associated with maternal factors. First, Lactobacillus and Streptococcus were more abundant in early lactation whereas the common oral (Leptotrichia) and environmental (Comamonas) bacteria were more abundant in established lactation. Second, Streptococcus,Lactobacillus,Lactococcus,Leuconostoc, and Micrococcus had a higher abundance in multiparous mothers compared with primiparous mothers. Third, a more diverse microbiota characterized by a higher abundance of lactic acid bacteria (Lactobacillus,Leuconostoc, and Lactococcus), Leucobacter, and Micrococcus was found in mothers with a healthy BMI. Finally, distinct microbial communities differed by stage of lactation and by exclusive, predominant, or mixed breastfeeding practices.

CONCLUSION

Milk bacterial communities in an indigenous community were associated with maternal factors. Higher microbial diversity was supported by having a healthy BMI, the absence of SCM, and by breastfeeding. Interestingly, breastfeeding practices when assessed by lactation stage were associated with distinct microbiota profiles.

The "weanling's dilemma" revisited: Evolving bodies of evidence and the problem of infant paleodietary interpretation

Breastfeeding is known to be a powerful mediator of maternal and childhood health, with impacts throughout the life course. Paleodietary studies of the past 30 years have accordingly taken an enduring interest in the health and diet of young children as a potential indicator of population fertility, subsistence, and mortality patterns. While progress has been made in recent decades toward acknowledging the agency of children, many paleodietary reconstructions have failed to incorporate developments in cognate disciplines revealing synergistic dynamics between maternal and offspring biology. Paleodietary interpretation has relied heavily on the "weanling's dilemma," in which infants are thought to face a bleak choice between loss of immunity or malnutrition. Using a review of immunological and epidemiological evidence for the dynamic and supportive role that breastfeeding plays throughout the complementary feeding period, this article offers context and nuance for understanding past feeding transitions. We suggest that future interpretative frameworks for infant paleodietary and bioarchaeological research should include a broad knowledge base that keeps pace with relevant developments outside of those disciplines.

Capturing the diversity of the human milk microbiota through culture-enriched molecular profiling: a feasibility study

Previous human milk studies have confirmed the existence of a highly diverse bacterial community using culture-independent and targeted culture-dependent techniques. However, culture-enriched molecular profiling of milk microbiota has not been done. Additionally, the impact of storage conditions and milk fractionation on microbiota composition is not understood. In this feasibility study, we optimized and applied culture-enriched molecular profiling to study culturable milk microbiota in eight milk samples collected from mothers of infants admitted to a neonatal intensive care unit. Fresh samples were immediately plated or stored at -80°C for 2 weeks (short-term frozen). Long-term samples were stored at -20°C for >6 months. Samples were cultured using 10 different culture media and incubated both aerobically and anaerobically. We successfully isolated major milk bacteria, including Streptococcus, Staphylococcus and Bifidobacterium, from fresh milk samples, but were unable to culture any bacteria from the long-term frozen samples. Short-term freezing shifted the composition of viable milk bacteria from the original composition in fresh samples. Nevertheless, the inter-individual variability of milk microbiota composition was observed even after short-term storage. There was no major difference in the overall milk microbiota composition between milk fractions in this feasibility study. This is among the first studies on culture-enriched molecular profiling of the milk microbiota demonstrating the effect of storage and fractionation on milk microbiota composition.

The Microbiota of the Human Mammary Ecosystem

Human milk contains a dynamic and complex site-specific microbiome, which is not assembled in an aleatory way, formed by organized microbial consortia and networks. Presence of some genera, such as Staphylococcus, Streptococcus, Corynebacterium, Cutibacterium (formerly known as Propionibacterium), Lactobacillus, Lactococcus and Bifidobacterium, has been detected by both culture-dependent and culture-independent approaches. DNA from some gut-associated strict anaerobes has also been repeatedly found and some studies have revealed the presence of cells and/or nucleic acids from viruses, archaea, fungi and protozoa in human milk. Colostrum and milk microbes are transmitted to the infant and, therefore, they are among the first colonizers of the human gut. Still, the significance of human milk microbes in infant gut colonization remains an open question. Clinical studies trying to elucidate the question are confounded by the profound impact of non-microbial human milk components to intestinal microecology. Modifications in the microbiota of human milk may have biological consequences for infant colonization, metabolism, immune and neuroendocrine development, and for mammary health. However, the factors driving differences in the composition of the human milk microbiome remain poorly known. In addition to colostrum and milk, breast tissue in lactating and non-lactating women may also contain a microbiota, with implications in the pathogenesis of breast cancer and in some of the adverse outcomes associated with breast implants. This and other open issues, such as the origin of the human milk microbiome, and the current limitations and future prospects are addressed in this review.

Isolation and characterization of lactic acid bacteria from human milk

Human milk is the main source of nutrition for infants and the transmission of various microorganisms. The lactic acid bacteria (LAB) in breast milk allow for the establishment of the gut microflora of infants. In this study, we aimed to assess the probiotic potential of LAB strains isolated from breast milk of healthy Chinese women. Two strains, Lacticaseibacillus rhamnosus (formerly Lactobacillus rhamnosus) LHL6 and LHL7, were selected and identified through morphology observation, Gram staining, and 16S rDNA phylogenetic analysis. Using Limosilactobacillus fermentum (formerly Lactobacillus fermentum) CECT5716 as the standard reference strain, the screened strains were characterized for aspects of growth, production of lactic acid and H₂O₂, antibiotic susceptibility, survival under simulated gastrointestinal conditions, and tolerance to cadmium (Cd). In de Man, Rogosa, and Sharpe (MRS) broth, LHL6 and LHL7 showed longer lag phases than CECT5716 but higher specific growth rates. For the production of lactic acid and H₂O₂, LHL7 performed better than LHL6 and CECT5716, indicating better antimicrobial ability. Strain LHL7 generated 9.99 mg/L H₂O₂, considerably higher than 1.25 mg/L for LHL6 and 2.33 mg/L for CECT5716. According to European Food Safety Authority minimum inhibitory concentrations, all of the investigated strains were resistant to chloramphenicol, streptomycin, and kanamycin. However, unlike LHL6 and CECT5716, LHL7 was susceptible to ampicillin and resistant to tetracycline. Resistance to azithromycin, cephalexin, and penicillin G were similar for all 3 strains, whereas CECT5716 was resistant to a higher concentration of roxithromycin. All 3 strains were able to survive in a simulated gastric-like solution, but a low percentage survived in the presence of 0.4% bile salt and 7% pancreatin. Encapsulation with protectants may enhance the survival rate. All 3 strains were tolerant to 500 mg/L Cd in MRS broth and to 1,000 mg/L Cd on MRS agar medium. In summary, 2 novel strains of LAB were obtained that have similar characteristics to the reference strain CECT5716. This work identified potential probiotic candidates for application in the food and pharmaceutical industries and facilitated identification of further probiotics.

Lactobacillus commensals autochthonous to human milk have the hallmarks of potent probiotics

Maternal milk is an important source of essential nutrients for the optimal growth of infants. Breastfeeding provides a continuous supply of beneficial bacteria to colonize the infant gastrointestinal tract (GIT) and offers health benefits for disease prevention and immunity. The purpose of this study was to isolate novel probiotic strains from the breast milk of native Pakistani mothers and to evaluate their probiotic potential. We isolated 21 strains of bacteria from the colostrum and mature milk of 20 healthy mothers, who had vaginal deliveries and were not taking antibiotics. After phenotypic and genotypic characterization, these isolates were tested for survival in the GIT using in vitro acid and bile tests. Nine strains showing good acid tolerance were assessed for their growth rate, bile resistance and ability to hydrolyze bile salts. Out of the four Lactobacillus isolates adjudged to be most promising as probiotics, three were Lactobacillus fermentum strains and one was a strain of Lactobacillus oris. This study demonstrates that human milk is a viable source of commensal bacteria beneficial to both adults and babies.

Effect of Sample Collection (Manual Expression vs. Pumping) and Skimming on the Microbial Profile of Human Milk Using Culture Techniques and Metataxonomic Analysis

Human milk microbiota is a unique bacterial community playing a relevant role in infant health, but its composition depends on different factors (woman health, lactation stage, and geographical lactation). However, information is lacking regarding some other factors that may affect the bacterial community of human milk. In this study we aimed to study the impact of the sample collection method and the skimming procedure using culture-dependent and culture-independent techniques to study the human milk microbial profile. One set of milk samples was provided by women (n = 10) in two consecutive days; half of the samples were collected the first day by manual expression and the other half on the second day by pumping. The rest of the participants (n = 17) provided milk samples that were fractionated by centrifugation; the bacterial profiles of whole milk and skimmed milk were compared by culture techniques in 10 milk samples, while those of whole milk, fat and skimmed milk were subjected to metataxonomic analysis in seven samples. Globally, the results obtained revealed high interindividual variability but that neither the use of single-use sterile devices to collect the sample nor the skimming procedure have a significant impact of the microbial profile of human samples.

Effect of Maternal Diet and Milk Lipid Composition on the Infant Gut and Maternal Milk Microbiomes

Inter-subject variability in human milk microbiome is well known; however, its origins and possible relationship to the mother’s diet are still debated. We investigated associations between maternal nutrition, milk fatty acids composition and microbiomes in mother–infant dyads. Breast milk and infant fecal samples were collected across three time points (one week, one month and three months postpartum) from 22 mother–infant pairs. Food frequency questionnaires for the months of pregnancy and three months postpartum were collected. Milk fatty acids were analyzed by GC–MS and the microbiome in breast milk and infant feces was determined by 16S rRNA sequencing. Statistical interactions were computed using Spearman’s method and corrected for multiple comparisons. We found significant negative correlation between Streptococcus relative abundance in maternal milk and intake of unsaturated fatty acids and folic acid at one month postpartum. At three months postpartum, vitamin B-12 consumption was significantly associated with a single operational taxonomic unit belonging to Streptococcus. Comparison between milk microbiome and lipid composition showed, one-month postpartum, significant negative correlation between Streptococcus relative abundance and the abundance of oleic acid. Additional correlations were detected between Staphylococcus hominis and two medium-chain saturated fatty acids. Our results reinforce the hypothesis that maternal nutrition may affect milk microbiome.

Human Milk's Hidden Gift: Implications of the Milk Microbiome for Preterm Infants' Health

Breastfeeding is considered the gold standard for infants' nutrition, as mother's own milk (MOM) provides nutritional and bioactive factors functional to optimal development. Early life microbiome is one of the main contributors to short and long-term infant health status, with the gut microbiota (GM) being the most studied ecosystem. Some human milk (HM) bioactive factors, such as HM prebiotic carbohydrates that select for beneficial bacteria, and the specific human milk microbiota (HMM) are emerging as early mediators in the relationship between the development of GM in early life and clinical outcomes. The beneficial role of HM becomes even more crucial for preterm infants, who are exposed to significant risks of severe infection in early life as well as to adverse short and long-term outcomes. When MOM is unavailable or insufficient, donor human milk (DHM) constitutes the optimal nutritional choice. However, little is known about the specific effect of DHM on preterm GM and its potential functional implication on HMM. The purpose of this narrative review is to summarize recent findings on HMM origin and composition and discuss the role of HMM on infant health and development, with a specific focus on preterm infants.

Host Microbe Interactions in the Lactating Mammary Gland

The bacteria present in human milk constitute the human milk microbiome (hMM). Both the older culture-based work and the more recent studies using molecular detection of bacterial DNA have reached similar conclusions: the hMM mostly consists of commensal staphylococci such as Staphylococcus epidermidis, and streptococci. The prevalence of other bacterial groups such lactobacilli varies widely, while the abundance and prevalence of bifidobacteria is generally low. Recently, the hMM became accepted as a part of a physiologically normal state with suggested potential health benefits. Most research on the hMM has focused on its composition and potential effect on the breastfed infant. A major role as a microbiome inoculum for the infant gut has been proposed, but remains to be clearly demonstrated. Herein, we also discuss the emerging connection between the hMM and mammary gland physiology and lactation. Similarities between the mammary gland and mucosal interfaces are considerable, and in particular mucosal-like immune attributes of mammary gland. The potential role of hMM-host interactions in the mammary gland in maternal health is explored with a primary focus on lactational mastitis.

Culture Dependent and Independent Analysis of Potential Probiotic Bacterial Genera and Species Present in the Phyllosphere of Raw Eaten Produce

The plant phyllosphere is colonized by a complex ecosystem of microorganisms. Leaves of raw eaten vegetables and herbs are habitats for bacteria important not only to the host plant, but also to human health when ingested via meals. The aim of the current study was to determine the presence of putative probiotic bacteria in the phyllosphere of raw eaten produce. Quantification of bifidobacteria showed that leaves of Lepidium sativum L., Cichorium endivia L., and Thymus vulgaris L. harbor between 10³ and 10⁶ DNA copies per gram fresh weight. Total cultivable bacteria in the phyllosphere of those three plant species ranged from 10⁵ to 10⁸ CFU per gram fresh weight. Specific enrichment of probiotic lactic acid bacteria from C. endivia, T. vulgaris,Trigonella foenum-graecum L., Coriandrum sativum L., and Petroselinum crispum L. led to the isolation of 155 bacterial strains, which were identified as Pediococcus pentosaceus, Enterococcus faecium, and Bacillus species, based on their intact protein pattern. A comprehensive community analysis of the L. sativum leaves by PhyloChip hybridization revealed the presence of genera Bifidobacterium, Lactobacillus, and Streptococcus. Our results demonstrate that the phyllosphere of raw eaten produce has to be considered as a substantial source of probiotic bacteria and point to the development of vegetables and herbs with added probiotic value.

Composition and Variation of the Human Milk Microbiota Are Influenced by Maternal and Early-Life Factors

Breastmilk contains a complex community of bacteria that may help seed the infant gut microbiota. The composition and determinants of milk microbiota are poorly understood. Among 393 mother-infant dyads from the CHILD cohort, we found that milk microbiota at 3-4 months postpartum was dominated by inversely correlated Proteobacteria and Firmicutes, and exhibited discrete compositional patterns. Milk microbiota composition and diversity were associated with maternal factors (BMI, parity, and mode of delivery), breastfeeding practices, and other milk components in a sex-specific manner. Causal modeling identified mode of breastfeeding as a key determinant of milk microbiota composition. Specifically, providing pumped breastmilk was consistently associated with multiple microbiota parameters including enrichment of potential pathogens and depletion of bifidobacteria. Further, these data support the retrograde inoculation hypothesis, whereby the infant oral cavity impacts the milk microbiota. Collectively, these results identify features and determinants of human milk microbiota composition, with potential implications for infant health and development.

Unfolding the Human Milk Microbiome Landscape in the Omics Era

Studies conducted in the last years have demonstrated that human milk represents a continuous supply of beneficial bacteria to the infant gut, which contribute to the maturation of the digestive and immune functions in the developing infant. Nevertheless, the origin of bacterial populations in milk is not fully understood yet and they have been proposed to originate from maternal skin, infant’s mouth, and (or) endogenously, from the maternal digestive tract through a mechanism involving immune cells. Understanding the composition, functions and assembly of the human milk microbiota has important implications not only for the infant gut microbiota establishment, but also for the mammary health since dysbiosis in the milk bacteria may lead to mastitis. Besides, host, microbial, medical and environmental factors may affect the composition of the human milk microbiome, with implications for the mother-infant health. Application of both culture-dependent and -independent techniques to assess the milk microbiome faces some practical limitations but, together, have allowed providing novel and complementary views on its origin, composition and functioning as summarized in this minireview. In the next future, the application of the ultimate advances in next-generation sequencing and omics approaches, including culturomics, will allow a detailed and comprehensive understanding of the composition and functions of these microbial communities, including their interactions with other milk components, expanding the opportunities to design novel microbiome-based modulation strategies for this ecosystem.

A Review of Bioactive Factors in Human Breastmilk: A Focus on Prematurity

Preterm birth is an increasing worldwide problem. Prematurity is the second most common cause of death in children under 5 years of age. It is associated with a higher risk of several pathologies in the perinatal period and adulthood. Maternal milk, a complex fluid with several bioactive factors, is the best option for the newborn. Its dynamic composition is influenced by diverse factors such as maternal age, lactation period, and health status. The aim of the present review is to summarize the current knowledge regarding some bioactive factors present in breastmilk, namely antioxidants, growth factors, adipokines, and cytokines, paying specific attention to prematurity. The revised literature reveals that the highest levels of these bioactive factors are found in the colostrum and they decrease along the lactation period; bioactive factors are found in higher levels in preterm as compared to full-term milk, they are lacking in formula milk, and decreased in donated milk. However, there are still some gaps and inconclusive data, and further research in this field is needed. Given the fact that many preterm mothers are unable to complete breastfeeding, new information could be important to develop infant supplements that best match preterm human milk.

Geographical location specific composition of cultured microbiota and Lactobacillus occurrence in human breast milk in China

Breast milk bacteria play an important role in the early development of the gut microbiota and the immune system. Dominant living bacteria of 89 healthy Chinese women from 11 cities in five regions were analysed by broad-range yeast extract, casitone, and fatty acid and de Man, Rogosa, and Sharpe-based culturing coupled with 16S rRNA sequence and quantitative polymerase chain reaction. Principal coordinate analysis showed that human breast milk samples were classified into three groups, driven by Enterococcus (abundance in group 1, 63.13%), Streptococcus (abundance in group 2, 68.16%) and Staphylococcus (abundance in group 3, 55.17%). The microbiota profile was highly region-specific. Samples from the Northwest and North of China showed higher alpha diversity compared to other regions (p < 0.05). Staphylococcus, Streptococcus, and Enterococcus were the dominant genera in all samples. Lactobacillus had a high occurrence in samples from the Northwest and North, dominated by Lactobacillus reuteri and Lactobacillus gasseri. Samples of mothers with a high postpartum body mass index showed more Staphylococcus and less Lactobacillus and Streptococcus. Staphylococcus was negatively correlated with Lactobacillus and Streptococcus. The mode of delivery also affected the composition of microbiota, even after culture. These findings indicate differences between the North and South, provide effective information for collection of samples in which Lactobacillus is the predominant genus, and lower the detection limit for small amounts of bacteria.

Integrated Analysis of Human Milk Microbiota With Oligosaccharides and Fatty Acids in the CHILD Cohort

Background: Human milk contains many bioactive components that are typically studied in isolation, including bacteria. We performed an integrated analysis of human milk oligosaccharides and fatty acids to explore their associations with milk microbiota.

Methods: We studied a sub-sample of 393 mothers in the CHILD birth cohort. Milk was collected at 3–4 months postpartum. Microbiota was analyzed by 16S rRNA gene V4 sequencing. Oligosaccharides and fatty acids were analyzed by rapid high-throughput high performance and gas liquid chromatography, respectively. Dimension reduction was performed with principal component analysis for oligosaccharides and fatty acids. Center log-ratio transformation was applied to all three components. Associations between components were assessed using Spearman rank correlation, network visualization, multivariable linear regression, redundancy analysis, and structural equation modeling. P-values were adjusted for multiple comparisons. Key covariates were considered, including fucosyltransferase-2 (FUT2) secretor status of mother and infant, method of feeding (direct breastfeeding or pumped breast milk), and maternal fish oil supplement use.

Results: Overall, correlations were strongest between milk components of the same type. For example, FUT2-dependent HMOs were positively correlated with each other, and Staphylococcus was negatively correlated with other core taxa. Some associations were also observed between components of different types. Using redundancy analysis and structural equation modeling, the overall milk fatty acid profile was significantly associated with milk microbiota composition. In addition, some individual fatty acids [22:6n3 (docosahexaenoic acid), 22:5n3, 20:5n3, 17:0, 18:0] and oligosaccharides (fucosyl-lacto-N-hexaose, lacto-N-hexaose, lacto-N-fucopentaose I) were associated with microbiota α diversity, while others (C18:0, 3′-sialyllactose, disialyl-lacto-N-tetraose) were associated with overall microbiota composition. Only a few significant associations between individual HMOs and microbiota were observed; notably, among mothers using breast pumps, Bifidobacterium prevalence was associated with lower abundances of disialyl-lacto-N-hexaose. Additionally, among non-secretor mothers, Staphylococcus was positively correlated with sialylated HMOs.

Conclusion: Using multiple approaches to integrate and analyse milk microbiota, oligosaccharides, and fatty acids, we observed several associations between different milk components and microbiota, some of which were modified by secretor status and/or breastfeeding practices. Additional research is needed to further validate and mechanistically characterize these associations and determine their relevance to infant gut and respiratory microbiota development and health.

Milk Therapy: Unexpected Uses for Human Breast Milk

BACKGROUND

Human breast milk provides a child with complete nutrition but is also a popular therapeutic remedy that has been used in traditional, natural pharmacopeia, and ethnomedicine for many years. The aim of this current review is to summarize studies of non-nutritional uses of mothers' milk.

METHODS

Two databases (PubMed and Google Scholar) were searched with a combination of twelve search terms. We selected articles that were published between 1 January 2010, and 1 January 2019. The language of publication was limited to English.

RESULTS

Fifteen studies were included in the systematic review. Ten of these were randomized controlled trials, one was a quasi-experimental study, two were in vitro studies, and four employed an animal research model.

CONCLUSIONS

Many human milk components have shown promise in preclinical studies and are undergoing active clinical evaluation. The protective and treatment role of fresh breast milk is particularly important in areas where mothers and infants do not have ready access to medicine.

Stem cells in human breast milk

Recent studies have demonstrated that breast milk contains a population of cells displaying many of the properties typical of stem cells. This review outlines progress made in this newly emerging field of stem cell biology and provides an analysis of the available data on purification, propagation and differentiation of certain types of progenitor cells from breast milk. The possible fates of breast milk cells, including microchimerism caused by their transmission to the distant organs of the infant, are also discussed. Unique properties of breast milk-derived stem cells, such as their unusually low tumorigenic potential and their negligible ability to form teratomas, are highlighted as obvious advantages for using these cells in regenerative therapy.

Evaluation of Potential Probiotics Isolated from Human Milk and Colostrum

Several studies have demonstrated a diversity of bacterial species in human milk, even in aseptically collected samples. The present study evaluated potential probiotic bacteria isolated from human milk and associated maternal variables. Milk samples were collected from 47 healthy women and cultured on selective and universal agar media under aerobic and anaerobic conditions. Bacterial isolates were counted and identified by Biotyper Matrix-Assisted Laser Desorption Ionization-Time of Flight mass spectrometry and then tested for probiotic properties. Total bacteria in human milk ranged from 1.5 to 4.0 log₁₀ CFU/mL. The higher bacterial counts were found in colostrum (mean = 3.9 log₁₀ CFU/mL, 95% CI 3.14-4.22, p = 0.00001). The most abundant species was Staphylococcus epidermidis (n = 76). The potential probiotic candidates were Lactobacillus gasseri (n = 4), Bifidobacterium breve (n = 1), and Streptococcus salivarius (n = 4). Despite the small sample size, L. gasseri was isolated only in breast milk from mothers classified into a normal weight range and after a vaginally delivered partum. No potential probiotics showed antagonism against pathogens, but all of them agglutinated different pathogens. Nine bacterial isolates belonging to the species L. gasseri, B. breve, and S. salivarius were selected as potential probiotics. The present study confirms the presence in breast milk of a bacterial microbiota that could be the source of potential probiotic candidates to be used in the formula of simulated maternal milk.

Impact of nutrition and rotavirus infection on the infant gut microbiota in a humanized pig model

BACKGROUND

Human rotavirus (HRV) is a major cause of viral gastroenteritis in infants; particularly in developing countries where malnutrition is prevalent. Malnutrition perturbs the infant gut microbiota leading to sub-optimal functioning of the immune system and further predisposing infants to enteric infections. Therefore, we hypothesized that malnutrition exacerbates rotavirus disease severity in infants.

METHODS

In the present study, we used a neonatal germ free (GF) piglets transplanted with a two-month-old human infant's fecal microbiota (HIFM) on protein deficient and sufficient diets. We report the effects of malnourishment on the HRV infection and the HIFM pig microbiota in feces, intestinal and systemic tissues, using MiSeq 16S gene sequencing (V4-V5 region).

RESULTS

Microbiota analysis indicated that the HIFM transplantation resulted in a microbial composition in pigs similar to that of the original infant feces. This model was then used to understand the interconnections between microbiota diversity, diet, and HRV infection. Post HRV infection, HIFM pigs on the deficient diet had lower body weights, developed more severe diarrhea and increased virus shedding compared to HIFM pigs on sufficient diet. However, HRV induced diarrhea and shedding was more pronounced in non-colonized GF pigs compared to HIFM pigs on either sufficient or deficient diet, suggesting that the microbiota alone moderated HRV infection. HRV infected pigs on sufficient diet showed increased microbiota diversity in intestinal tissues; whereas, greater diversity was observed in systemic tissues of HRV infected pigs fed with deficient diet.

CONCLUSIONS

These results suggest that proper nourishment improves the microbiota quality in the intestines, alleviates HRV disease and lower probability of systemic translocation of potential opportunistic pathogens/pathobionts. In conclusion, our findings further support the role for microbiota and proper nutrition in limiting enteric diseases.

Human Breast Milk: Exploring the Linking Ring Among Emerging Components

Maternal breast milk (BM) is a complex and unique fluid that evolution adapted to satisfy neonatal needs; in addition to classical nutrients, it contains several bioactive components. BM characteristically shows inter-individual variability, modifying its composition during different phases of lactation. BM composition, determining important consequences on neonatal gut colonization, influences both short and long-term development. Maternal milk can also shape neonatal microbiota, through its glycobiome rich in Lactobacilli spp. and Bifidobacteria spp. Therefore, neonatal nourishment during the first months of life seems the most important determinant of individual's outcomes. Our manuscript aims to provide new evidence in the characterization of BM metabolome and microbiome, and its comparison to formula milk, allowing the evaluation of each nutrient's influence on neonatal metabolism. This result very interesting since potentially offers an innovative approach to investigate the complex relationship between BM components and infant's health, also providing the chance to intervene in a sartorial way on diet composition, according to the nutritional requests. Future research, integrating metabolomics, microbiomics and stem cells knowledge, could make significant steps forward in understanding BM extraordinary properties and functions.

Infectious Agents in Childhood Leukemia

Acute leukemia is the most common pediatric cancer, representing one-third of all cancers that occurs in under 15 year olds, with a varied incidence worldwide. Although a number of advances have increased the knowledge of leukemia pathophysiology, its etiology remains less well understood. The role of infectious agents, such as viruses, bacteria, or parasites, in the pathogenesis of leukemia has been discussed. To date, several cellular mechanisms involving infectious agents have been proposed to cause leukemia following infections. However, although leukemia can be triggered by contact with such agents, they can also be beneficial in developing immune stimulation and protection despite the risk of leukemic clones. In this review, we analyze the proposed hypotheses concerning how infectious agents may play a role in the origin and development of leukemia, as well as in a possible mechanism of protection following infections. We review reported clinical observations associated with vaccination or breastfeeding, that support hypotheses such as early life exposure and the resulting early immune stimulation that lead to protection.

Amino acid supplements and metabolic health: a potential interplay between intestinal microbiota and systems control

Dietary supplementation of essential amino acids (EAAs) has been shown to promote healthspan. EAAs regulate, in fact, glucose and lipid metabolism and energy balance, increase mitochondrial biogenesis, and maintain immune homeostasis. Basic science and epidemiological results indicate that dietary macronutrient composition affects healthspan through multiple and integrated mechanisms, and their effects are closely related to the metabolic status to which they act. In particular, EAA supplementation can trigger different and even opposite effects depending on the catabolic and anabolic states of the organisms. Among others, gut-associated microbial communities (referred to as gut microbiota) emerged as a major regulator of the host metabolism. Diet and host health influence gut microbiota, and composition of gut microbiota, in turn, controls many aspects of host health, including nutrient metabolism, resistance to infection, and immune signals. Altered communication between the innate immune system and the gut microbiota might contribute to complex diseases. Furthermore, gut microbiota and its impact to host health change largely during different life phases such as lactation, weaning, and aging. Here we will review the accumulating body of knowledge on the impact of dietary EAA supplementation on the host metabolic health and healthspan from a holistic perspective. Moreover, we will focus on the current efforts to establish causal relationships among dietary EAAs, gut microbiota, and health during human development.

Human Milk Microbial Community Structure Is Relatively Stable and Related to Variations in Macronutrient and Micronutrient Intakes in Healthy Lactating Women

Background: The human milk microbiome has been somewhat characterized, but little is known about changes over time and relations with maternal factors such as nutrient intake.Objective: We sought to characterize the human milk microbiome and described associations with maternal nutrient intake, time postpartum, delivery mode, and body mass index (BMI; in kg/m²).Methods: Milk samples (n = 104) and 24-h diet recalls were collected 9 times from 21 healthy lactating women from day 2 to 6 mo postpartum. Women were classified by BMI as healthy weight (<25) or overweight or obese (≥25). Bacterial taxa were characterized with the use of the high-throughput sequencing of the 16S ribosomal RNA gene.Results: The milk microbiome was relatively constant over time, although there were small changes in some of the lesser-abundant genera. Relative abundances of several taxa were associated with BMI, delivery mode, and infant sex. For instance, overweight and obese mothers produced milk with a higher relative abundance of Granulicatella than did healthy-weight women (1.8% ± 0.6% compared with 0.4% ± 0.2%, respectively; P < 0.05). Relative abundances of several bacterial taxa were also associated with variations in maternal dietary intake. For example, intakes of saturated fatty acids (r_s = -0.59; P = 0.005) and monounsaturated fatty acids (r_s = -0.46; P = 0.036) were inversely associated with the relative abundance of Corynebacterium; total carbohydrates (r_s = -0.54; P = 0.011), disaccharides (r_s = -0.47; P = 0.031), and lactose (r_s = -0.51; P = 0.018) were negatively associated with Firmicutes; and protein consumption was positively correlated with the relative abundance of Gemella (r_s = 0.46; P = 0.037).Conclusions: Factors associated with variations in the human milk microbiome are complex and may include maternal nutrient intake, maternal BMI, delivery mode, and infant sex. Future studies designed to investigate the relation between maternal nutrient intake and the milk microbiome should strive to also evaluate dietary supplement usage and analyze the collected milk for its nutrient content.

Human Milk and Allergic Diseases: An Unsolved Puzzle

There is conflicting evidence on the protective role of breastfeeding in relation to the development of allergic sensitisation and allergic disease. Studies vary in methodology and definition of outcomes, which lead to considerable heterogeneity. Human milk composition varies both within and between individuals, which may partially explain conflicting data. It is known that human milk composition is very complex and contains variable levels of immune active molecules, oligosaccharides, metabolites, vitamins and other nutrients and microbial content. Existing evidence suggests that modulation of human breast milk composition has potential for preventing allergic diseases in early life. In this review, we discuss associations between breastfeeding/human milk composition and allergy development.

Relationships Among Microbial Communities, Maternal Cells, Oligosaccharides, and Macronutrients in Human Milk

BACKGROUND

Human milk provides all essential nutrients necessary for early life and is rich in nonnutrients, maternally derived (host) cells, and bacteria, but almost nothing is known about the interplay among these components. Research aim: The primary objective of this research was to characterize relationships among macronutrients, maternal cells, and bacteria in milk.

METHODS

Milk samples were collected from 16 women and analyzed for protein, lipid, fatty acid, lactose, and human milk oligosaccharide concentrations. Concentrations of maternal cells were determined using microscopy, and somatic cell counts were enumerated. Microbial ecologies were characterized using culture-independent methods.

RESULTS

Absolute and relative concentrations of maternal cells were mostly consistent within each woman as were relative abundances of bacterial genera, and there were many apparent relationships between these factors. For instance, relative abundance of Serratia was negatively associated with somatic cell counts ( r = -.47, p < .0001) and neutrophil concentration ( r = -.38, p < .0006). Concentrations of several oligosaccharides were correlated with maternally derived cell types as well as somatic cell counts; for example, lacto-N-tetraose and lacto-N-neotetraose were inversely correlated with somatic cell counts ( r = -.64, p = .0082; r = -.52, p = .0387, respectively), and relative abundance of Staphylococcus was positively associated with total oligosaccharide concentration ( r = .69, p = .0034). Complex relationships between milk nutrients and bacterial community profile, maternal cells, and milk oligosaccharides were also apparent.

CONCLUSION

These data support the possibility that profiles of maternally derived cells, nutrient concentrations, and the microbiome of human milk might be interrelated.

Cells of human breast milk

Human milk is a complex fluid that has developed to satisfy the nutritional requirements of infants. In addition to proteins, lipids, carbohydrates and other biologically active components, breast milk contains a diverse microbiome that is presumed to colonize the infant gastrointestinal tract and a heterogeneous population of cells with unclear physiological roles and health implications. Noteworthy cellular components of breast milk include progenitor/stem cells. This review summarizes the current state of knowledge of breast milk cells, including leukocytes, epithelial cells, stem cells and potentially probiotic bacteria.

Innate Immunity and Breast Milk

Human milk is a dynamic source of nutrients and bioactive factors; unique in providing for the human infant's optimal growth and development. The growing infant's immune system has a number of developmental immune deficiencies placing the infant at increased risk of infection. This review focuses on how human milk directly contributes to the infant's innate immunity. Remarkable new findings clarify the multifunctional nature of human milk bioactive components. New research techniques have expanded our understanding of the potential for human milk's effect on the infant that will never be possible with milk formulas. Human milk microbiome directly shapes the infant's intestinal microbiome, while the human milk oligosaccharides drive the growth of these microbes within the gut. New techniques such as genomics, metabolomics, proteomics, and glycomics are being used to describe this symbiotic relationship. An expanded role for antimicrobial proteins/peptides within human milk in innate immune protection is described. The unique milieu of enhanced immune protection with diminished inflammation results from a complex interaction of anti-inflammatory and antioxidative factors provided by human milk to the intestine. New data support the concept of mucosal-associated lymphoid tissue and its contribution to the cellular content of human milk. Human milk stem cells (hMSCs) have recently been discovered. Their direct role in the infant for repair and regeneration is being investigated. The existence of these hMSCs could prove to be an easily harvested source of multilineage stem cells for the study of cancer and tissue regeneration. As the infant's gastrointestinal tract and immune system develop, there is a comparable transition in human milk over time to provide fewer immune factors and more calories and nutrients for growth. Each of these new findings opens the door to future studies of human milk and its effect on the innate immune system and the developing infant.

Gut microbiome as a clinical tool in gastrointestinal disease management: are we there yet?

Spurred on by ever-evolving developments in analytical methodology, the microbiome, and the gut microbiome in particular, has become the hot topic in biomedical research. Ingenious experiments in animal models have revealed the extent to which the gut microbiota sustains health and how its disruption might contribute to disease pathogenesis. Not surprisingly, associations between the microbiota and disease states in humans have been the subject of considerable interest and many links proposed. However, with rare exceptions, the incrimination of an altered microbiota in disease pathogenesis seems premature at this time given our incomplete understanding of the composition of the gut microbiota in health and the effect of many confounding factors in the interpretation of supposedly abnormal microbial signatures. Future studies must account for these variables and the bidirectionality of host-microorganism interactions in health and disease. In this Perspectives, the status of microbiota signatures in the clinical arena (for facilitating diagnosis or refining prognosis) will be critically assessed and guidance toward future progress provided.

Development of the cutaneous microbiome in the preterm infant: A prospective longitudinal study

Background

Neonatal sepsis in preterm infants is often due to organisms that colonize the skin including Staphylococcus spp. and Candida spp. Development and maturation of the skin microbiome in the neonatal period, especially in preterm infants, may be critical in preventing colonization with pathogens and subsequent progression to neonatal sepsis. Development of the skin microbiome in preterm infants or its determinants in the first 4 weeks of life has not been evaluated.

Methods

We evaluated the skin microbiome from three body sites, antecubital fossa, forehead and gluteal region, in a prospective cohort of 15 preterm (birth weight < 1500 g and < 32 weeks of gestation) and 15 term neonates. The microbiome community membership and relative abundance were evaluated by amplification and sequencing the bacterial V3-V5 region of the16S rRNA gene on the 454 GS FLX platform. We used linear mixed effects models to analyze longitudinal data.

Results

The structure and composition of the skin microbiome did not differ between the three sampling sites for term and preterm infants in the neonatal period. However, skin bacterial richness was positively associated with gestational age in the first four weeks of life. Intravenous antibiotics negatively impacted the bacterial diversity of the skin but we did not see differences with respect to feeding or mode of delivery.

Conclusions

Gestational age, which influences the maturity of skin structure and function, is associated with the development of the preterm cutaneous microbiome. Understanding the maturation of a healthy skin microbiome, prevention of pathogen colonization and its role in the development of immunity will be pivotal in the development of novel interventions to prevent infections in critically ill preterm infants.

Intervention strategies for cesarean section-induced alterations in the microbiota-gut-brain axis

Microbial colonization of the gastrointestinal tract is an essential process that modulates host physiology and immunity. Recently, researchers have begun to understand how and when these microorganisms colonize the gut and the early-life factors that impact their natural ecological establishment. The vertical transmission of maternal microbes to the offspring is a critical factor for host immune and metabolic development. Increasing evidence also points to a role in the wiring of the gut-brain axis. This process may be altered by various factors such as mode of delivery, gestational age at birth, the use of antibiotics in early life, infant feeding, and hygiene practices. In fact, these early exposures that impact the intestinal microbiota have been associated with the development of diseases such as obesity, type 1 diabetes, asthma, allergies, and even neurodevelopmental disorders. The present review summarizes the impact of cesarean birth on the gut microbiome and the health status of the developing infant and discusses possible preventative and restorative strategies to compensate for early-life microbial perturbations.

Got bacteria? The astounding, yet not-so-surprising, microbiome of human milk

Contrary to long-held dogma, human milk is not sterile. Instead, it provides infants a rich source of diverse bacteria, particularly microbes belonging to the Staphylococcus, Streptococcus, and Pseudomonas genera. Very little is known about factors that influence variation in the milk microbiome among women and populations, although time postpartum, delivery mode, and maternal factors such as diet and antibiotic use might be important. The origins of the bacteria in milk are thought to include the maternal gastrointestinal tract (via an entero-mammary pathway) and through bacterial exposure of the breast during nursing. Currently, almost nothing is known about whether variation in microbe consumption by the infant via human milk and that of the mammary gland, itself, impacts short-term and/or long-term infant and maternal health although several studies suggest this is likely. We urge the clinical and public health communities to be patient, however, in order to allow human milk and lactation researchers to first understand what constitutes 'normal' in terms of the milk microbiome (as well as factors that impact microbial community structure) prior to jumping the gun to investigate if and how this important source of microbes impacts maternal and infant health.

The human milk microbiome and factors influencing its composition and activity

Beyond its nutritional aspects, human milk contains several bioactive compounds, such as microbes, oligosaccharides, and other substances, which are involved in host-microbe interactions and have a key role in infant health. New techniques have increased our understanding of milk microbiota composition, but few data on the activity of bioactive compounds and their biological role in infants are available. Whereas the human milk microbiome may be influenced by specific factors - including genetics, maternal health and nutrition, mode of delivery, breastfeeding, lactation stage, and geographic location - the impact of these factors on the infant microbiome is not yet known. This article gives an overview of milk microbiota composition and activity, including factors influencing microbial composition and their potential biological relevance on infants' future health.