A Scoping Review of Research on the Human Milk Microbiome

Antimicrobial Stewardship: A Correct Management to Reduce Sepsis in NICU Settings

The discovery of antimicrobial drugs has led to a significant increase in survival from infections; however, they are very often prescribed and administered, even when their use is not necessary and appropriate. Newborns are particularly exposed to infections due to the poor effectiveness and the immaturity of their immune systems. For this reason, in Neonatal Intensive Care Units (NICUs), the use of antimicrobial drugs is often decisive and life-saving, and it must be started promptly to ensure its effectiveness in consideration of the possible rapid evolution of the infection towards sepsis. Nevertheless, the misuse of antibiotics in the neonatal period leads not only to an increase in the development and wide spreading of antimicrobial resistance (AMR) but it is also associated with various short-term (e.g., alterations of the microbiota) and long-term (e.g., increased risk of allergic disease and obesity) effects. It appears fundamental to use antibiotics only when strictly necessary; specific decision-making algorithms and electronic calculators can help limit the use of unnecessary antibiotic drugs. The aim of this narrative review is to summarize the right balance between the risks and benefits of antimicrobial therapy in NICUs; for this purpose, specific Antimicrobial Stewardship Programs (ASPs) in neonatal care and the creation of a specific antimicrobial stewardship team are requested.

Peer-to-Peer Human Milk-Sharing Among Israeli Milk Donors: A Mixed-Methods Study in the Land of Milk and Honey

BACKGROUND

Evidence is lacking on the phenomenon of peer-to-peer human milk-sharing in the Middle East, specifically, in Israel.

RESEARCH AIMS

This study aimed to uncover peer-to-peer human milk-sharing in Israel, learn about how and whether donors engage in safe milk handling and storage practices, and assess knowledge about human milk and breastfeeding among this milk-sharing population. We also aimed to investigate donors' selectiveness in their decisions about to whom they donate their milk and their perceptions about the sale and purchase of human milk.

METHODS

We conducted a semi-structured online survey, including both closed- and open-ended questions and used mixed methods to analyze responses descriptively. We used non-probability sampling to obtain a broad sample of human milk donors.

RESULTS

Out of 250 completed surveys, most participants (87.2%, n = 218) reported engaging in safe milk-sharing practices and were generally knowledgeable about the health risks associated with milk-sharing. Participant religiosity was associated with somewhat lower hygiene practices (r = -0.15, p ≤ .05). Most of the participants (81.7%, n = 190) were against the sale of human milk. Participants generally expressed no preference about the recipient of their milk, with some exceptions.

CONCLUSION

The milk-handling and storage practices of the participants in this study suggest a need to improve knowledge and awareness of safe milk storage temperature and the importance of washing hands before pumping milk, particularly within the religious sector. We propose that guidelines about safe milk-sharing practices be written and adopted by the Israeli Ministry of Health, and communicated through pediatricians, family doctors, nurses in Mother and Child Clinics (In Hebrew: Tipat Halav), and social media.

The First 1000 Days of Life: How Changes in the Microbiota Can Influence Food Allergy Onset in Children

BACKGROUND

Allergic disease, including food allergies (FA)s, has been identified as a major global disease. The first 1000 days of life can be a "window of opportunity" or a "window of susceptibility", during which several factors can predispose children to FA development. Changes in the composition of the gut microbiota from pregnancy to infancy may play a pivotal role in this regard: some bacterial genera, such as Lactobacillus and Bifidobacterium, seem to be protective against FA development. On the contrary, Clostridium and Staphylococcus appear to be unprotective.

METHODS

We conducted research on the most recent literature (2013-2023) using the PubMed and Scopus databases. We included original papers, clinical trials, meta-analyses, and reviews in English. Case reports, series, and letters were excluded.

RESULTS

During pregnancy, the maternal diet can play a fundamental role in influencing the gut microbiota composition of newborns. After birth, human milk can promote the development of protective microbial species via human milk oligosaccharides (HMOs), which play a prebiotic role. Moreover, complementary feeding can modify the gut microbiota's composition.

CONCLUSIONS

The first two years of life are a critical period, during which several factors can increase the risk of FA development in genetically predisposed children.

A Scoping Review of Neonatal Opioid Withdrawal and the Infant Gut Microbiome: Does Human Milk Optimize Infant Outcomes?

BACKGROUND

While a growing body of literature has established the role of human milk as a mechanism of protection in the formation of the infant gut microbiome, it remains unclear the extent to which this association exists for infants with neonatal opioid withdrawal syndrome.

PURPOSE

The purpose of this scoping review was to describe the current state of the literature regarding the influence of human milk on infant gut microbiota in infants with neonatal opioid withdrawal syndrome.

DATA SOURCES

CINAHL, PubMed, and Scopus databases were searched for original studies published from January 2009 through February 2022. Additionally, unpublished studies across relevant trial registries, conference proceedings, websites, and organizations were reviewed for possible inclusion. A total of 1610 articles met selection criteria through database and register searches and 20 through manual reference searches.

STUDY SELECTION

Inclusion criteria were primary research studies, written in English, published between 2009 and 2022, including a sample of infants with neonatal opioid withdrawal syndrome/neonatal abstinence syndrome, and focusing on the relationship between the receipt of human milk and the infant gut microbiome.

DATA EXTRACTION

Two authors independently conducted title/abstract and full-text review until there was consensus of study selection.

RESULTS

No studies satisfied the inclusion criteria, which resulted in an empty review.

IMPLICATIONS FOR PRACTICE AND RESEARCH

Findings from this study document the paucity of data exploring the associations between human milk, the infant gut microbiome, and subsequent neonatal opioid withdrawal syndrome. Further, these results highlight the timely importance of prioritizing this area of scientific inquiry.

Maternal weight status and the composition of the human milk microbiome: A scoping review

The human milk microbiome is thought to partly contribute to the assembly of the infant gut microbiome, a microbial community with important implications for infant health and development. While obesity has well-established links with the adult gut microbiome, less is known about how it affects the human milk microbiome. In this scoping review, we synthesize the current literature on the microbial composition of human milk by maternal weight status, defined broadly as BMI (prepregnancy and postpartum) and gestational weight gain (GWG). This study followed the a priori protocol published in Prospero (registration #: CRD42020165633). We searched the following databases for studies reporting maternal weight status and a characterization of milk microbiota through culture-dependent and culture-independent methods: MEDLINE, Embase, Web of Science, CINAHL, and Scopus. After screening 6,365 studies, we found 20 longitudinal and cross-sectional studies investigating associations between maternal weight status and the composition of the milk microbiome. While some studies reported no associations, many others reported that women with a pre-pregnancy or postpartum BMI characterized as overweight or obese, or with excessive GWG, had higher abundances of the genus Staphylococcus, lower Bifidobacterium abundance, and lower alpha diversity (within-sample diversity). This review suggests that maternal weight status is minorly associated with the composition of the milk microbiome in various ways. We offer potential explanations for these findings, as well as suggestions for future research.

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.

Composition of Human Breast Milk Microbiota and Its Role in Children's Health

Human milk contains a number of nutritional and bioactive molecules including microorganisms that constitute the so-called "Human Milk Microbiota (HMM)". Recent studies have shown that not only bacterial but also viral, fungal, and archaeal components are present in the HMM. Previous research has established, a "core" microbiome, consisting of Firmicutes (i.e., Streptococcus, Staphylococcus), Proteobacteria (i.e., Serratia, Pseudomonas, Ralstonia, Sphingomonas, Bradyrhizobium), and Actinobacteria (i.e., Propionibacterium, Corynebacterium). This review aims to summarize the main characteristics of HMM and the role it plays in shaping a child's health. We reviewed the most recent literature on the topic (2019-2021), using the PubMed database. The main sources of HMM origin were identified as the retrograde flow and the entero-mammary pathway. Several factors can influence its composition, such as maternal body mass index and diet, use of antibiotics, time and type of delivery, and mode of breastfeeding. The COVID-19 pandemic, by altering the mother-infant dyad and modifying many of our previous habits, has emerged as a new risk factor for the modification of HMM. HMM is an important contributor to gastrointestinal colonization in children and therefore, it is fundamental to avoid any form of perturbation in the HMM that can alter the microbial equilibrium, especially in the first 100 days of life. Microbial dysbiosis can be a trigger point for the development of necrotizing enterocolitis, especially in preterm infants, and for onset of chronic diseases, such as asthma and obesity, later in life.

Neonatal Feeding Tube Colonization and the Potential Effect on Infant Health: A Review

Background

Infants in the neonatal intensive care unit (NICU) often require feeding tubes (FT) for weeks to months. Because FTs are in near constant contact with human milk and/or formula, rapid and extensive bacterial growth is possible. Due to their immature immunologic and gastrointestinal (GI) systems, infants may be at significant health risk due to FT colonization. In adults, length of time FTs remain in place (dwell time) affects the degree of colonization and biofilm formation which is important in infants whose tubes remain in place up to 30 days.

Objective

The purpose of this review was to describe and summarize the evidence regarding FT bacterial colonization in infants and identify gaps needing further investigation.

Methods

Medline, CINAHL, and Embase databases were searched for clinical and/or laboratory-based observational and randomized controlled studies investigating the presence of bacteria in neonatal FTs.

Results

This review of 10 studies found evidence that neonatal FTs may contain high quantities of potentially pathogenic and antibiotic resistant bacteria and longer dwell times may increase the bacterial load. Furthermore, evidence suggests FT colonization may be nosocomial in origin and contribute to adverse infant health. Feeding tubes are an unrecognized source of bacterial colonization which may increase morbidity in premature infants and thus the presence of bacteria in FTs is an important area of investigation in the nutritional care of vulnerable infants in the NICU.

Implications

Further appropriately powered studies which are clinically based, use appropriate analyses, and control for potential covariates are necessary to make clinical recommendations.

Traditional plant use during lactation and postpartum recovery: Infant development and maternal health roles

ETHNOPHARMACOLOGICAL RELEVANCE

Evidence of phytochemical roles in infant development and maternal recovery offers insights into beneficial functions of traditional plant use during lactation and the postpartum period. Ethnopharmacological research has relevance to global priorities on maternal and child health, to understanding origins and determinants of human self-medication, and for reconciling traditional postpartum practices and mainstream healthcare.

AIM OF THE STUDY

Present emerging evidence, within evolutionary and socio-cultural contexts, on the role of maternal consumption on transfer of phytochemicals into breast milk with impacts on maternal and child health, and on infant development. Establish current state of knowledge and an ethnopharmacological research agenda that is attentive to cross-cultural and regional differences in postpartum plant use.

MATERIALS AND METHODS

An extensive literature review using Medline, Scopus, and Web of Science focused on traditional and contemporary use and socio-cultural context, as well as physiological, pharmacological, toxicological, and behavioral activities of plants used medicinally by women during postpartum recovery and lactation.

RESULTS

The most widely reported postpartum plants show antimicrobial, anti-inflammatory, immunological, and neurophysiological activities, with low toxicity. Phytochemicals transfer from maternal consumption into breast milk in physiological concentrations, while animal studies demonstrate immunomodulation and other actions of medicinal plants during lactation. Reporting on the use and diverse traditional knowledge of women about plants during the postpartum period is obscured by the marginal place of obstetric issues and by gender biases in ethnobotanical research. In many contemporary contexts use is prejudiced by precautionary risk warnings in health literature and practice that confound lactation with pregnancy.

CONCLUSIONS

Although systematic investigation of postpartum plant use is lacking, known pharmacological activities support potential benefits on infant development and maternal health with immediate and long-term consequences in relation to allergic, inflammatory, autoimmune, and other diseases. An ethnopharmacological agenda focused on the perinatal period requires directed methodologies and a regional approach in relation to culturally-specific knowledge and practices, traditional plant use, and local health needs. Testing the hypothesis that phytochemicals transferred from medicinal plants into breast milk impact the human immune system and other aspects of infant development requires extended analysis of phytochemicals in human milk and infant lumen and plasma, as well as effects on gastrointestinal and milk microbiome.

Impact of Intrapartum Antibiotic Prophylaxis for Group B Streptococcus on the Term Infant Gut Microbiome: A State of the Science Review

Since the implementation of screening and prophylaxis guidelines for group B streptococcus (GBS) in the early 1990s there has been considerable advancement in scientific knowledge about the gut microbiome and its role in both health and disease processes. Research assessing early influences during the development of the infant gut microbiome has advanced considerably in the last 15 years. It is now widely accepted that early introduction of antibiotics in infancy is associated with increased risk for illness later in life. Research on antibiotic administration to pregnant individuals during labor for GBS colonization and its potential impact on the developing gut microbiome of term infants is now emerging. Despite the growing body of evidence of the negative impact of antibiotics on the gut microbiome, the guidelines for GBS prophylaxis among pregnant individuals have not changed significantly since their inception in the 1990s. This state of the science review examines the association between intrapartum antibiotic administration and alterations in the gut microbiome of term infants born vaginally, specifically in relation to microbial composition; the occurrence of and effect on antibiotic resistance genes in the infant gut; and the factors that may compound or mitigate these effects.

Beyond maternal care: The effects of extra-maternal influences within the maternal environment on offspring neurodevelopment and later-life behavior

The early-life maternal environment has a profound and persistent effect on offspring neuroendocrine function, neurotransmitter systems, and behavior. Studies using rodent models suggest that early-life maternal care can influence the 'developmental programming' of offspring in part through altered epigenetic regulation of specific genes. The exploration of epigenetic regulation of these genes as a biological mechanism has been important to our understanding of how animals adapt to their environments and how these developmental trajectories may be altered. However, other non-maternal factors have been shown to act directly, or to interact with maternal care, to influence later-life phenotype. Based on accumulating evidence, including our research, we discuss other important influences on the developmental programming of offspring. We highlight early-life variations in temperature exposure and offspring genotype x environment interactions as prominent examples. We conclude with recommendations for future investigations on how early-life maternal care and extra-maternal influences lead to persistent changes in the brain and behavior of the offspring throughout development.

Enteral Bioactive Factor Supplementation in Preterm Infants: A Systematic Review

Feeding preterm infants with mother’s own milk is associated with a reduction in postnatal complications and an improved neurocognitive outcome. Therefore, the bioactive factor composition of human milk has been used as a tool for the development of nutritional supplements with a potential prophylactic or therapeutic effect. The aim of this systematic review was to provide an overview on bioactive factors which have been studied as supplement to enteral nutrition in randomized controlled trials, and to provide an overview of ongoing trials. MEDLINE, EMBASE, CENTRAL, and clinical trial registers were searched. Studies on the antimicrobial protein lactoferrin were excluded as these were summarized very recently in three separate systematic reviews. Studies on vitamins D, K and iron were also excluded as they are already incorporated in most international guidelines. We identified 17 different bioactive factors, which were investigated in 26 studies. Despite the encouraging potential effects of several bioactive factors, more high-quality studies with a sufficient number of preterm infants are required before a certain factor may be implemented into clinical practice. Three large trials (n > 500) that investigate the effects of either enteral insulin or vitamin A are currently ongoing and could provide more definite answers on these specific supplements.