A Solution to Antifolate Resistance in Group B Streptococcus: Untargeted Metabolomics Identifies Human Milk Oligosaccharide-Induced Perturbations That Result in Potentiation of Trimethoprim

Interactions of human milk oligosaccharides with the immune system

Human milk oligosaccharides (HMOs) are abundant, diverse and complex sugars present in human breast milk. HMOs are well-characterized barriers to microbial infection and by modulating the human microbiome they are also thought to be nutritionally beneficial to the infant. The structural variety of over 200 HMOs, including neutral, fucosylated and sialylated forms, allows them to interact with the immune system in various ways. Clinically, HMOs impact allergic diseases, reducing autoimmune and inflammatory responses, and offer beneficial support to the preterm infant immune health. This review examines the HMO composition and associated immunomodulatory effects, including interactions with immune cell receptors and gut-associated immune responses. These immunomodulatory properties highlight the potential for HMO use in early stage immune development and for use as novel immunotherapeutics. HMO research is rapidly evolving and promises innovative treatments for immune-related conditions and improved health outcomes.

Antibiotic perturbations to the gut microbiome

Antibiotic-mediated perturbation of the gut microbiome is associated with numerous infectious and autoimmune diseases of the gastrointestinal tract. Yet, as the gut microbiome is a complex ecological network of microorganisms, the effects of antibiotics can be highly variable. With the advent of multi-omic approaches for systems-level profiling of microbial communities, we are beginning to identify microbiome-intrinsic and microbiome-extrinsic factors that affect microbiome dynamics during antibiotic exposure and subsequent recovery. In this Review, we discuss factors that influence restructuring of the gut microbiome on antibiotic exposure. We present an overview of the currently complex picture of treatment-induced changes to the microbial community and highlight essential considerations for future investigations of antibiotic-specific outcomes. Finally, we provide a synopsis of available strategies to minimize antibiotic-induced damage or to restore the pretreatment architectures of the gut microbial community.

The Utility of Human Milk Oligosaccharides against Group B Streptococcus Infections of Reproductive Tissues and Cognate Adverse Pregnancy Outcomes

Preterm birth affects nearly 10% of all pregnancies in the United States, with 40% of those due, in part, to infections. Streptococcus agalactiae (Group B Streptococcus, GBS) is one of the most common perinatal pathogens responsible for these infections. Current therapeutic techniques aimed to ameliorate invasive GBS infections are less than desirable and can result in complications in both the neonate and the mother. To this end, the need for novel therapeutic options is urgent. Human milk oligosaccharides (HMOs), an integral component of human breast milk, have been previously shown to possess antiadhesive and antimicrobial properties. To interrogate these characteristics, we examined HMO-mediated outcomes in both in vivo and ex vivo models of GBS infection utilizing a murine model of ascending GBS infection, an EpiVaginal human organoid tissue model, and ex vivo human gestational membranes. Supplementation of HMOs resulted in diminished adverse pregnancy outcomes, decreased GBS adherence to gestational tissues, decreased colonization within the reproductive tract, and reduced proinflammatory immune responses to GBS infection. Taken together, these results highlight the potential of HMOs as promising therapeutic interventions in perinatal health.

Anti-biofilm Activity of Human Milk Oligosaccharides in Clinical Strains of Streptococcus agalactiae with Diverse Capsular and Sequence Types

Group B Streptococcus (GBS) is an encapsulated Gram-positive bacterial pathogen that causes severe perinatal infections. Human milk oligosaccharides (HMOs) are short-chain sugars that have recently been shown to possess antimicrobial and anti-biofilm activity against a variety of bacterial pathogens, including GBS. We have expanded these studies to demonstrate that HMOs can inhibit and dismantle biofilm in both invasive and colonizing strains of GBS. A cohort of 30 diverse strains of GBS were analyzed for susceptibility to HMO-dependent biofilm inhibition or destruction. HMOs were significantly effective at inhibiting biofilm in capsular-type- and sequence-type-specific fashion, with significant efficacy in CpsIb, CpsII, CpsIII, CpsV, and CpsVI strains as well as ST-1, ST-12, ST-19, and ST-23 strains. Interestingly, CpsIa as well as ST-7 and ST-17 were not susceptible to the anti-biofilm activity of HMOs, underscoring the strain-specific effects of these important antimicrobial molecules against the perinatal pathogen Streptococcus agalactiae.

Recent advances on human milk oligosaccharide antimicrobial activity

Over the past century, human health has been enhanced by antimicrobial development. Following the deployment of the first antibiotics in the 1940s, bacterial resistance evolved and has increasingly outmaneuvered even the most promising antimicrobial agents. Accordingly, increased interest has been placed on alternative methods to circumvent antimicrobial resistance evolution. In the enclosed short review, we discuss the antimicrobial properties of human breast milk with a special emphasis on human milk oligosaccharides (HMOs). We recount studies across gram-negative and gram-positive pathogens, highlighting the usage of HMOs in promoting human health and wellness.

Non-Digestible Oligosaccharides: A Novel Treatment for Respiratory Infections?

Emerging antimicrobial resistance in respiratory infections requires novel intervention strategies. Non-digestible oligosaccharides (NDOs) are a diverse group of carbohydrates with broad protective effects. In addition to promoting the colonization of beneficial gut microbiota and maintaining the intestinal homeostasis, NDOs act as decoy receptors, effectively blocking the attachment of pathogens on host cells. NDOs also function as a bacteriostatic agent, inhibiting the growth of specific pathogenic bacteria. Based on this fact, NDOs potentiate the actions of antimicrobial drugs. Therefore, there is an increasing interest in characterizing the anti-infective properties of NDOs. This focused review provides insights into the mechanisms by which representative NDOs may suppress respiratory infections by targeting pathogens and host cells. We summarized the most interesting mechanisms of NDOs, including maintenance of gut microbiota homeostasis, interference with TLR-mediated signaling, anti-oxidative effects and bacterial toxin neutralization, bacteriostatic and bactericidal effects, and anti-adhesion or anti-invasive properties. A detailed understanding of anti-infective mechanisms of NDOs against respiratory pathogens may contribute to the development of add-on therapy or alternatives to antimicrobials.

Detailed Characterization of Antipathogenic Properties of Human Milk N-Glycome, against Staphylococcus aureus, Indicating Its Targeting on Cell Surface Proteins

Human milk N-glycome was previously identified to have strong antipathogenic activities. This study is aimed to characterize the detailed antibacterial properties and the potential function mechanism of human milk N-glycome against Staphylococcus aureus. A serials of traditional antibacterial assays showed that human milk N-glycome possessed both bacteriostatic and bactericidal activities, which was further confirmed by the cell structure disruption including the change of transmembrane potential and leakage of intracellular contents. The results of the bacterial surface zeta potential and hydrophobicity, bacterial binding assay, gel shift assay, and fluorescence spectra and the different synergistic effects of human milk N-glycome combined with different antibiotics indicated that the bacterial surface proteins could be the targets of human milk N-glycome. Moreover, human milk N-glycome also showed antibiofilm activity. In conclusion, human milk N-glycome exhibited good potential for acting as an antibacterial substance against S. aureus and the antibacterial mechanism was a cell surface targeting action.

Galacto-Oligosaccharide Supplementation Modulates Pathogen-Commensal Competition between Streptococcus agalactiae and Streptococcus salivarius

The members of the infant microbiome are governed by feeding method (breastmilk vs. formula). Regardless of the source of nutrition, a competitive growth advantage can be provided to commensals through prebiotics - either human milk oligosaccharides (HMOs) or plant oligosaccharides that are supplemented into formula. To characterize how prebiotics modulate commensal - pathogen interactions, we have designed and studied a minimal microbiome where a pathogen, Streptococcus agalactiae engages with a commensal, Streptococcus salivarius. We discovered that while S. agalactiae suppresses the growth of S. salivarius via increased lactic acid production, galacto-oligosaccharides (GOS) supplementation reverses the effect. This result has major implications in characterizing how single species survive in the gut, what niche they occupy, and how they engage with other community members.

The Diverse Antimicrobial Activities of Human Milk Oligosaccharides against Group B Streptococcus

Streptococcus agalactiae or Group B Streptococcus (GBS) is a Gram-positive bacterial pathobiont that is the etiological cause of severe perinatal infections. GBS can colonize the vagina of pregnant patients and invade tissues causing ascending infections of the gravid reproductive tract that lead to adverse outcomes including preterm birth, neonatal sepsis, and maternal or fetal demise. Additionally, transmission of GBS during labor or breastfeeding can also cause invasive infections of neonates and infants. However, human milk has also been shown to have protective effects against infection; a characteristic that is likely derived from antimicrobial and immunomodulatory properties of molecules that comprise human milk. Recent evidence suggests that human milk oligosaccharides (HMOs), short-chain sugars that comprise 8-20 % of breast milk, have antimicrobial and anti-biofilm activity against GBS and other bacterial pathogens. Additionally, HMOs have been shown to potentiate the activity of antibiotics against GBS. This review presents the most recent published work that studies the interaction between HMOs and GBS.

Human Milk Oligosaccharides Reduce Murine Group B Streptococcus Vaginal Colonization with Minimal Impact on the Vaginal Microbiota

Group B Streptococcus (GBS) colonizes the vaginal mucosa of a significant percentage of healthy women and is a leading cause of neonatal bacterial infections. Currently, pregnant women are screened in the last month of pregnancy, and GBS-positive women are given antibiotics during parturition to prevent bacterial transmission to the neonate. Recently, human milk oligosaccharides (HMOs) isolated from breastmilk were found to inhibit GBS growth and biofilm formation in vitro, and women that make certain HMOs are less likely to be vaginally colonized with GBS. Using in vitro human vaginal epithelial cells and a murine vaginal colonization model, we tested the impact of HMO treatment on GBS burdens and the composition of the endogenous microbiota by 16S rRNA amplicon sequencing. HMO treatment reduced GBS vaginal burdens in vivo with minimal alterations to the vaginal microbiota. HMOs displayed potent inhibitory activity against GBS in vitro, but HMO pretreatment did not alter adherence of GBS or the probiotic Lactobacillus rhamnosus to human vaginal epithelial cells. In addition, disruption of a putative GBS glycosyltransferase (Δsan_0913) rendered the bacterium largely resistant to HMO inhibition in vitro and in vivo but did not compromise its adherence, colonization, or biofilm formation in the absence of HMOs. We conclude that HMOs are a promising therapeutic bioactive to limit GBS vaginal colonization with minimal impacts on the vaginal microenvironment.

IMPORTANCE During pregnancy, GBS ascension into the uterus can cause fetal infection or preterm birth. In addition, GBS exposure during labor creates a risk of serious disease in the vulnerable newborn and mother postpartum. Current recommended prophylaxis consists of administering broad-spectrum antibiotics to GBS-positive mothers during labor. Although antibiotics have significantly reduced GBS neonatal disease, there are several unintended consequences, including altered neonatal gut bacteria and increased risk for other types of infection. Innovative preventions displaying more targeted antimicrobial activity, while leaving the maternal microbiota intact, are thus appealing. Using a mouse model, we found that human milk oligosaccharides (HMOs) reduce GBS burdens without perturbing the vaginal microbiota. We conclude that HMOs are a promising alternative to antibiotics to reduce GBS neonatal disease.

Antibiofilm Activity of Human Milk Oligosaccharides against Multidrug Resistant and Susceptible Isolates of Acinetobacter baumannii

Acinetobacter baumannii is a serious threat to human health, per the Centers for Disease Control and Prevention's latest threat assessment. A. baumannii is a Gram-negative opportunistic bacterial pathogen that causes severe community and nosocomial infections in immunocompromised patients. Treatment of these infections is confounded by the emergence of multi- and pan-drug resistant strains of A. baumannii. A. baumannii colonizes abiotic and biotic surfaces and evades antimicrobial challenges by forming biofilms, which are three-dimensional architectural structures of cells adhered to a substrate and encased in an extracellular matrix comprised of polymeric substances such as polysaccharides, proteins, and DNA. Biofilm-inhibiting compounds have recently gained attention as a chemotherapeutic strategy to prevent or disperse A. baumannii biofilms and restore the utility of traditional antimicrobial strategies. Recent work indicates that human milk oligosaccharides (HMOs) have potent antibacterial and biofilm-inhibiting properties. We sought to test the utility of HMOs against a bank of clinical isolates of A. baumannii to ascertain changes in bacterial growth or biofilm formation. Our results indicate that out of 18 strains tested, 14 were susceptible to the antibiofilm activities of HMOs, and that the potent antibiofilm activity was observed in strains isolated from diverse anatomical sites, disease manifestations, and across antibiotic-resistant and susceptible strains.

Probing morphological, genetic and metabolomic changes of in vitro embryo development in a microfluidic device

Assisted reproduction technologies for clinical and research purposes rely on a brief in vitro embryo culture which, despite decades of progress, remain suboptimal in comparison to the physiological environment. One promising tool to improve this technique is the development of bespoke microfluidic chambers. Here we present and validate a new microfluidic device in polydimethylsiloxane (PDMS) for the culture of early mouse embryos. Device material and design resulted embryo compatible and elicit minimal stress. Blastocyst formation, hatching, attachment and outgrowth formation on fibronectin-coated devices were similar to traditional microdrop methods. Total blastocyst cell number and allocation to the trophectoderm and inner cell mass lineages were unaffected. The devices were designed for culture of 10-12 embryos. Development rates, mitochondrial polarization and metabolic turnover of key energy substrates glucose, pyruvate and lactate were consistent with groups of 10 embryos in microdrop controls. Increasing group size to 40 embryos per device was associated with increased variation in development rates and altered metabolism. Device culture did not perturb blastocyst gene expression but did elicit changes in embryo metabolome, which can be ascribed to substrate leaching from PDMS and warrant further investigation.

Synthesis as an Expanding Resource in Human Milk Science

Few classes of natural products rival the structural audacity of oligosaccharides. Their complexity, however, has stood as an immense roadblock to translational research, as access to homogeneous material from nature is challenging. Thus, while carbohydrates are critical to the myriad functional and structural aspects of the biological sciences, their behavior is largely descriptive. This challenge presents an attractive opportunity for synthetic chemistry, particularly in the area of human milk science. First, there is an inordinate need for synthesizing homogeneous human milk oligosaccharides (HMOs). Superimposed on this goal is the mission of conducting syntheses at scale to enable animal studies. Herein, we present a personalized rumination of our involvement, and that of our colleagues, which has led to the synthesis and characterization of HMOs and mechanistic probes. Along the way, we highlight chemical, chemoenzymatic, and synthetic biology based approaches. We close with a discussion on emergent challenges and opportunities for synthesis, broadly defined, in human milk science.

Engineered Microbial Routes for Human Milk Oligosaccharides Synthesis

Human milk oligosaccharides (HMOs) are one of the important ingredients in human milk, which have attracted great interest due to their beneficial effect on the health of newborns. The large-scale production of HMOs has been researched using engineered microbial routes due to the availability, safety, and low cost of host strains. In addition, the development of molecular biology technology and metabolic engineering has promoted the effectiveness of HMOs production. According to current reports, 2'-fucosyllactose (2'-FL), 3-fucosyllactose (3-FL), lacto-N-tetraose (LNT), lacto-N-neotetraose (LNnT), 3'-sialyllactose (3'-SL), 6'-sialyllactose (6'-SL), and some fucosylated HMOs with complex structures have been produced via the engineered microbial route, with 2'-FL having been produced the most. However, due to the uncertainty of metabolic patterns, the selection of host strains has certain limitations. Aside from that, the expression of appropriate glycosyltransferase in microbes is key to the synthesis of different HMOs. Therefore, finding a safe and efficient glycosyltransferase has to be addressed when using engineered microbial pathways. In this review, the latest research on the production of HMOs using engineered microbial routes is reported. The selection of host strains and adapting different metabolic pathways helped researchers designing engineered microbial routes that are more conducive to HMOs production.

Metabolomic Analysis Evidences That Uterine Epithelial Cells Enhance Blastocyst Development in a Microfluidic Device

Here we report the use of a microfluidic system to assess the differential metabolomics of murine embryos cultured with endometrial cells-conditioned media (CM). Groups of 10, 1-cell murine B6C3F1 × B6D2F1 embryos were cultured in the microfluidic device. To produce CM, mouse uterine epithelial cells were cultured in potassium simplex optimized medium (KSOM) for 24 h. Media samples were collected from devices after 5 days of culture with KSOM (control) and CM, analyzed by reverse phase liquid chromatography and untargeted positive ion mode mass spectrometry analysis. Blastocyst rates were significantly higher (p < 0.05) in CM (71.8%) compared to control media (54.6%). We observed significant upregulation of 341 compounds and downregulation of 214 compounds in spent media from CM devices when compared to control. Out of these, 353 compounds were identified showing a significant increased abundance of metabolites involved in key metabolic pathways (e.g., arginine, proline and pyrimidine metabolism) in the CM group, suggesting a beneficial effect of CM on embryo development. The metabolomic study carried out in a microfluidic environment confirms our hypothesis on the potential of uterine epithelial cells to enhance blastocyst development. Further investigations are required to highlight specific pathways involved in embryo development and implantation.

Antibacterial and Anti-biofilm Activity of the Human Breast Milk Glycoprotein Lactoferrin against Group B Streptococcus

Group B Streptococcus (GBS) is an encapsulated Gram-positive human pathogen that causes invasive infections in pregnant hosts and neonates, as well as immunocompromised individuals. Colonization of the human host requires the ability to adhere to mucosal surfaces and circumnavigate the nutritional challenges and antimicrobial defenses associated with the innate immune response. Biofilm formation is a critical process to facilitate GBS survival and establishment of a replicative niche in the vertebrate host. Previous work has shown that the host responds to GBS infection by producing the innate antimicrobial glycoprotein lactoferrin, which has been implicated in repressing bacterial growth and biofilm formation. Additionally, lactoferrin is highly abundant in human breast milk and could serve a protective role against invasive microbial pathogens. This study demonstrates that human breast milk lactoferrin has antimicrobial and anti-biofilm activity against GBS and inhibits its adherence to human gestational membranes. Together, these results indicate that human milk lactoferrin could be used as a prebiotic chemotherapeutic strategy to limit the impact of bacterial adherence and biofilm formation on GBS-associated disease outcomes.

Prospecting Human Milk Oligosaccharides as a Defense Against Viral Infections

In addition to providing maximal nutritional value for neonatal growth and development, human milk functions as an early defense mechanism against invading pathogens. Human milk oligosaccharides (HMOs), which are abundant in human milk, are a diverse group of heterogeneous carbohydrates with wide ranging protective effects. In addition to promoting the colonization of beneficial intestinal flora, HMOs serve as decoy receptors, effectively blocking the attachment of pathogenic bacteria. HMOs also function as bacteriostatic agents, inhibiting the growth of gram-positive bacteria. Based on this precedence, an emerging area in the field has focused on characterizing the antiviral properties of HMOs. Indeed, HMOs have been evaluated as antiviral agents, with many possessing activity against life-threatening infections. This targeted review provides insight into the known glycan-binding interactions between select HMOs and influenza, rotavirus, respiratory syncytial virus, human immunodeficiency virus, and norovirus. Additionally, we review the role of HMOs in preventing necrotizing enterocolitis, an intestinal disease linked to viral infections. We close with a discussion of what is known broadly regarding human milk oligosaccharides and their interactions with coronaviruses.

Leveraging Stereoelectronic Effects in Biofilm Eradication: Synthetic β-Amino Human Milk Oligosaccharides Impede Microbial Adhesion As Observed by Scanning Electron Microscopy

Alongside Edward, Lemieux was among the earliest researchers studying negative hyperconjugation (i.e., the anomeric effect) or the preference for gauche conformations about the C1-O5 bond in carbohydrates. Lemieux also studied an esoteric, if not controversial, theory known as the reverse anomeric effect (RAE). This theory is used to rationalize scenarios where predicted anomeric stabilization does not occur. One such example is the Kochetkov amination where reducing end amines exist solely as the β-anomer. Herein, we provide a brief account of Lemieux's contributions to the field of stereoelectronics and apply this knowledge toward the synthesis of β-amino human milk oligosaccharides (βΑ-HMOs). These molecules were evaluated for their ability to inhibit growth and biofilm production in Group B Streptococcus (GBS) and Staphylococcus aureus. While the parent HMOs lacked antimicrobial and antibiofilm activity, their β-amino derivatives significantly inhibited biofilm formation in both species. Field emission gun-scanning single electron microscopy (FEG-SEM) revealed that treatment with β-amino HMOs significantly inhibits bacterial adherence and eliminates the ability of both microbes to form biofilms.

Like mother, like microbe: human milk oligosaccharide mediated microbiome symbiosis

Starting shortly after parturition, and continuing throughout our lifetime, the gut microbiota coevolves with our metabolic and neurological programming. This symbiosis is regulated by a complex interplay between the host and environmental factors, including diet and lifestyle. Not surprisingly, the development of this microbial community is of critical importance to health and wellness. In this targeted review, we examine the gut microbiome from birth to 2 years of age to characterize the role human milk oligosaccharides play in early formation of microbial flora.

Immunomodulation by Human Milk Oligosaccharides: The Potential Role in Prevention of Allergic Diseases

The prevalence and incidence of allergic diseases is rising and these diseases have become the most common chronic diseases during childhood in Westernized countries. Early life forms a critical window predisposing for health or disease. Therefore, this can also be a window of opportunity for allergy prevention. Postnatally the gut needs to mature, and the microbiome is built which further drives the training of infant's immune system. Immunomodulatory components in breastmilk protect the infant in this crucial period by; providing nutrients that contain substrates for the microbiome, supporting intestinal barrier function, protecting against pathogenic infections, enhancing immune development and facilitating immune tolerance. The presence of a diverse human milk oligosaccharide (HMOS) mixture, containing several types of functional groups, points to engagement in several mechanisms related to immune and microbiome maturation in the infant's gastrointestinal tract. In recent years, several pathways impacted by HMOS have been elucidated, including their capacity to; fortify the microbiome composition, enhance production of short chain fatty acids, bind directly to pathogens and interact directly with the intestinal epithelium and immune cells. The exact mechanisms underlying the immune protective effects have not been fully elucidated yet. We hypothesize that HMOS may be involved in and can be utilized to provide protection from developing allergic diseases at a young age. In this review, we highlight several pathways involved in the immunomodulatory effects of HMOS and the potential role in prevention of allergic diseases. Recent studies have proposed possible mechanisms through which HMOS may contribute, either directly or indirectly, via microbiome modification, to induce oral tolerance. Future research should focus on the identification of specific pathways by which individual HMOS structures exert protective actions and thereby contribute to the capacity of the authentic HMOS mixture in early life allergy prevention.