Antibacterial characteristics in the feces of breast-fed and formula-fed infants during the first year of life

Colostrum and Preterm Babies: A Systematic Review

Colostrum from mothers is rich in immunomodulating bio-factors such as immunoglobulins (IgA), lactoferrin, and oligosaccharides and supports gut microbial and inflammatory processes. The support in these processes may provide some relief for infants who are born pre-term. Pre-term infants are more likely to develop necrotizing enterocolitis (NEC), late-onset sepsis (LOS), and ventilator-acquired/associated pneumonia (VAP). Due to the components of colostrum, there may be incentives towards early administration for preterm infants. An extensive literature review was done using ProQuest, ScienceDirect, and PubMed. Only meta-analyses and experimental studies were used. The search included the keywords 'colostrum and preterm' and 'colostrum and necrotizing enterocolitis'. The initial search generated 13,543 articles and was narrowed to 25 articles through comprehensive inclusion and exclusion criteria. There were significantly higher levels of Lactobacillus and Bifidobacterium in pre-term infants given colostrum and a decrease in Moraxellaceae and Staphylococcaceae. Salivary secretory IgA increased following oral colostrum administration in pre-term infants along with downregulation of interleukin (IL)-1b and IL-8. It was also observed that tumor necrosis factor (TNF)-a, and interferon-gamma (IFN-g) were significantly higher in the control group. There was no significant difference in the incidence of LOS, NEC, or VAP between pre-term infants receiving colostrum and those who did not. Secondary outcomes such as time to full enteral feeding were improved in pre-term infants receiving oral colostrum in addition to reduced hospital stays. Lastly, there was no difference in mortality between pre-term infants that received colostrum compared to those who did not.

Clinical importance of immunonutrition in infants: a review of the recent literature

During the last decades, the role of nutrition has been well elucidated in medicine, especially among critically ill infants and children. Many nutrients have the potential to modulate the immune system. A healthy immune system is essential for the prevention and recovery of many pediatric illnesses. Intervention using specific nutrients for the immune system is called immunonutrition. Immunonutrient supplementation has been attempted to modulate inflammatory or immune responses, leading to an improved clinical course of critically ill patients with prolonged nutritional supplementation parenterally or enterally. This review discusses immunomodulatory nutrients for infants based on the recent literature.

Role of Human Milk Bioactives on Infants' Gut and Immune Health

Exclusive human milk feeding of the newborn is recommended during the first 6 months of life to promote optimal health outcomes during early life and beyond. Human milk contains a variety of bioactive factors such as hormones, cytokines, leukocytes, immunoglobulins, lactoferrin, lysozyme, stem cells, human milk oligosaccharides (HMOs), microbiota, and microRNAs. Recent findings highlighted the potential importance of adding HMOs into infant formula for their roles in enhancing host defense mechanisms in neonates. Therefore, understanding the roles of human milk bioactive factors on immune function is critical to build the scientific evidence base around breastfeeding recommendations, and to enhance positive health outcomes in formula fed infants through modifications to formulas. However, there are still knowledge gaps concerning the roles of different milk components, the interactions between the different components, and the mechanisms behind health outcomes are poorly understood. This review aims to show the current knowledge about HMOs, milk microbiota, immunoglobulins, lactoferrin, and milk microRNAs (miRNAs) and how these could have similar mechanisms of regulating gut and microbiota function. It will also highlight the knowledge gaps for future research.

Effects of Bovine Immunoglobulins on Immune Function, Allergy, and Infection

This review aims to provide an in depth overview of the current knowledge of the effects of bovine immunoglobulins on the human immune system. The stability and functional effects of orally ingested bovine immunoglobulins in milk products are described and potential mechanisms of action are discussed. Orally ingested bovine IgG (bovine IgG) can be recovered from feces, ranging from very low levels up to 50% of the ingested IgG that has passed through the gastrointestinal tract. In infants the recovered levels are higher than in adults most likely due to differences in stomach and intestinal conditions such as pH. This indicates that bovine IgG can be functionally active throughout the gastrointestinal tract. Indeed, a large number of studies in infants and adults have shown that bovine IgG (or colostrum as a rich source thereof) can prevent gastrointestinal tract infections, upper respiratory tract infections, and LPS-induced inflammation. These studies vary considerably in target group, design, source of bovine IgG, dosage, and endpoints measured making it hard to draw general conclusions on effectiveness of bovine immunoglobulin rich preparations. Typical sources of bovine IgG used in human studies are serum-derived IgG, colostrum, colostrum-derived IgG, or milk-derived immunoglobulins. In addition, many studies have used IgG from vaccinated cows, but studies using IgG from nonimmunized animals have also been reported to be effective. Mechanistically, bovine IgG binds to many human pathogens and allergens, can neutralize experimental infection of human cells, and limits gastrointestinal inflammation. Furthermore, bovine IgG binds to human Fc receptors which, enhances phagocytosis, killing of bacteria and antigen presentation and bovine IgG supports gastrointestinal barrier function in in vitro models. These mechanisms are becoming more and more established and explain why bovine IgG can have immunological effects in vivo. The inclusion of oral bovine immunoglobulins in specialized dairy products and infant nutrition may therefore be a promising approach to support immune function in vulnerable groups such as infants, children, elderly and immunocompromised patients.

Infant gut immunity: a preliminary study of IgA associations with breastfeeding

Secretory immunoglobulin A (IgA) plays a critical role in gut mucosal immune defense. Initially provided by breastmilk, IgA production by the infant gut is gradually stimulated by developing gut microbiota. This study reports associations between infant fecal IgA concentrations 4 months after birth, breastfeeding status and other pre/postnatal exposures in 47 infants in the Canadian Healthy Infant Longitudinal Development cohort. Breastfed infants and first-born infants had higher median fecal IgA concentrations (23.11 v. 9.34 µg/g protein, P<0.01 and 22.19 v. 8.23 µg/g protein, P=0.04). IgA levels increased successively with exclusivity of breastfeeding (β-coefficient, 0.37, P<0.05). This statistical association was independent of maternal parity and household pets. In the absence of breastfeeding, female sex and pet exposure elevated fecal IgA to levels found in breastfed infants. In addition to breastfeeding, infant fecal IgA associations with pre/postnatal exposures may affect gut immunity and risk of allergic disease.

Fetal programming of overweight through the microbiome: boys are disproportionately affected

Maternal and childhood obesity in pregnancy are worrisome public health issues facing our world today. New gene sequencing methods have advanced our knowledge of the disruptive effect of birth interventions and postnatal exposures on the maturation of gut microbiota and immunity during infancy. Yet, little is known about the impact of maternal pregnancy overweight on gut microbes and related processes, and how this may affect overweight risk in offspring. To address this gap in knowledge, we surveyed human studies for evidence in children, infants and pregnant women to piece together the limited literature and generate hypotheses for future investigation. From this literature, we learned that higher Lactobacillus yet lower Bacteroides spp. colonization of gut microbiota within 3 months of birth predicted risk for infant and child overweight. The abundance of bifidobacteria and staphylococci also appeared to play a role in the association with overweight, as did infant fecal immunoglobulin A levels, glycoproteins of the gut immune system that are acquired from breast milk and produced by the infant. We proposed that pregnancy overweight influences the compositional structure of gut microbiota in infants through vertical transfer of microbiota and/or their metabolites during pregnancy, delivery and breastfeeding. Finally, we brought forward emerging evidence on sex dimorphism, as well as ethnic and geographic variation, in reported associations between maternal overweight-induced gut microbiota dysbiosis and overweight risk.

Detection of sialic acid-utilising bacteria in a caecal community batch culture using RNA-based stable isotope probing

Sialic acids are monosaccharides typically found on cell surfaces and attached to soluble proteins, or as essential components of ganglioside structures that play a critical role in brain development and neural transmission. Human milk also contains sialic acid conjugated to oligosaccharides, glycolipids, and glycoproteins. These nutrients can reach the large bowel where they may be metabolised by the microbiota. However, little is known about the members of the microbiota involved in this function. To identify intestinal bacteria that utilise sialic acid within a complex intestinal community, we cultured the caecal microbiota from piglets in the presence of ¹³C-labelled sialic acid. Using RNA-based stable isotope probing, we identified bacteria that consumed ¹³C-sialic acid by fractionating total RNA in isopycnic buoyant density gradients followed by 16S rRNA gene analysis. Addition of sialic acid caused significant microbial community changes. A relative rise in Prevotella and Lactobacillus species was accompanied by a corresponding reduction in the genera Escherichia/Shigella, Ruminococcus and Eubacterium. Inspection of isotopically labelled RNA sequences suggests that the labelled sialic acid was consumed by a wide range of bacteria. However, species affiliated with the genus Prevotella were clearly identified as the most prolific users, as solely their RNA showed significantly higher relative shares among the most labelled RNA species. Given the relevance of sialic acid in nutrition, this study contributes to a better understanding of their microbial transformation in the intestinal tract with potential implications for human health.

Human lysozyme possesses novel antimicrobial peptides within its N-terminal domain that target bacterial respiration

Human milk lysozyme is thought to be a key defense factor in protecting the gastrointestinal tract of newborns against bacterial infection. Recently, evidence was found that pepsin, under conditions relevant to the newborn stomach, cleaves chicken lysozyme (cLZ) at specific loops to generate five antimicrobial peptide motifs. This study explores the antimicrobial role of the corresponding peptides of human lysozyme (hLZ), the actual protein in breast milk. Five peptide motifs of hLZ, one helix-loop-helix (HLH), its two helices (H1 and H2), and two helix-sheet motifs, H2-β-strands 1-2 (H2-S12) or H2-β-strands 1-3 (H2-S13), were synthesized and examined for antimicrobial action. The five peptides of hLZ exhibit microbicidal activity to various degrees against several bacterial strains. The HLH peptide and its N-terminal helix (H1) were significantly the most potent bactericidal to Gram-positive and Gram-negative bacteria and the fungus Candida albicans . Outer and inner membrane permeabilization studies, as well as measurements of transmembrane electrochemical potentials, provided evidence that HLH peptide and its N-terminal helix (H1) kill bacteria by crossing the outer membrane of Gram-negative bacteria via self-promoted uptake and are able to dissipate the membrane potential-dependent respiration of Gram-positive bacteria. This finding is the first to describe that hLZ possesses multiple antimicrobial peptide motifs within its N-terminal domain, providing insight into new classes of antibiotic peptides with potential use in the treatment of infectious diseases.

Influence of gestational age, cesarean section, and type of feeding on fecal human beta-defensin 2 and tumor necrosis factor-alpha

OBJECTIVE

: Development of the mucosal immune system is essential for controlling antigenic response. External factors are known to influence the immune system, such as breast-feeding or the mode of delivery. The aim of the present study was to investigate maturation of the enteric immune system.

PATIENTS AND METHODS

: In stool samples of 59 preterm and term-born infants we measured the concentration of human beta-defensin 2 (HBD 2), an endogenous antimicrobial peptide, and tumor necrosis factor-alpha (TNF-alpha), a cytokine playing a central role in mucosal inflammation, by enzyme-linked immunosorbent assay.

RESULTS

: Mode of delivery as well as nutrition (breast-feeding or formula) had no influence on the fecal concentration of HBD-2 or TNF-alpha, but there was a significant increase in the concentration of HBD-2 in correlation with gestational age. TNF-alpha showed no change in concentration.

CONCLUSIONS

: Low fecal HBD-2 may be a risk factor in preterm infants to develop neonatal enteric disease, such as necrotizing enterocolitis.

Use of probiotics in pediatrics: rationale, mechanisms of action, and practical aspects

The use of probiotics (ingested microbes that can modify intestinal microbial populations in a way that benefit the host) has moved from concept to actual demonstration of specific benefits by specific microorganisms for specific populations. It is increasingly clear that these benefits to the host are mostly mediated by the profound effect that intestinal microflora (microbiota) have on gut barrier function and host immune response. Intestinal bacteria are more numerous than the human cells of the host that harbors them. Despite having many potential pathogens in this microflora, humans do not routinely get infected. It is no coincidence that gut-associated immune tissue constitutes approximately 80% of all immunologically active cells in the human host. The gut interacts with intestinal bacteria, both resident and ingested, to develop protective mechanisms (via improving gut barrier function and immune stimulation for defense) and appropriate, nonexaggerated responses (via immune modulation and immune tolerance) to support host health. The mechanisms of this interaction between host and bacteria are increasingly being unraveled and in great part explain the clinical benefits that have been reported with specific probiotic bacteria by enhancing host defense mechanisms (such as for treatment and prevention of viral diarrhea and reducing risk of necrotizing enterocolitis), mitigating antibiotic-associated diarrhea, and modulating host immune response (such as in allergic disease).

Faecal SIgA secretion in infants fed on pre- or probiotic infant formula

Secretory immunoglobulin A (SIgA) plays an important role in the defence of the gastrointestinal tract. The level of faecal SIgA antibody is associated with increased neutralization and clearance of viruses. Formula-fed infants who lack the transfer of protective maternal SIgA from breast milk may benefit from strategies to support maturation of humoral immunity and endogenous production of SIgA. We aimed at studying the effects of standard, prebiotic and probiotic infant formulas on the faecal SIgA levels. At birth, infants of whom the mother had decided not to breastfeed were allocated to one of three formula groups in a randomized, double-blind fashion. Nineteen infants received standard infant formula; 19 received prebiotic formula containing a specific mixture of 0.6 g galacto-oligosaccharides (GOS)/fructo-oligosaccharides (FOS)/100 ml formula and 19 received probiotic formula containing 6.0 x 10(9) cfu Bifidobacterium animalis/100 ml formula. Faecal samples were taken on postnatal day 5, day 10, wk 4 and every 4 wk thereafter until wk 32. SIgA in faeces was determined by an enzyme-linked immunosorbent assay. During the intervention, infants fed on prebiotic formula showed a trend towards higher faecal SIgA levels compared with the standard formula-fed infants reaching statistical significance at the age of 16 wk. In contrast, infants fed on the probiotic formula showed a highly variable faecal SIgA concentration with no statistically significant differences compared with the standard formula group. Formula-fed infants may benefit from infant formulas containing a prebiotic mixture of GOS and FOS because of the observed clear tendency to increase faecal SIgA secretion. Adding viable B. animalis strain Bb-12 to infant formula did not reveal any sign for such a trend.

Processing of lysozyme at distinct loops by pepsin: A novel action for generating multiple antimicrobial peptide motifs in the newborn stomach

C-type lysozyme (cLZ) is an antimicrobial enzyme that plays a major defense role in many human secretions. Recently, we have identified a helix-loop-helix antimicrobial peptide fragment of cLZ. This finding suggests that processing by coexisting proteases might be a relevant physiological process for generating peptides that contribute to the in vivo mucosal defense role of cLZ. In this study, we found that pepsin, under condition relevant to the newborn stomach (pH 4.0), generated various peptides from cLZ with potent bactericidal activity against several strains of Gram-negative and Gram-positive bacteria. Microsequencing and mass spectral analysis revealed that pepsin cleavage occurred at conserved loops within the alpha-domain of cLZ. We found that the bactericidal domain, which was isolated by gel filtration and reversed-phase HPLC, contains two cationic alpha-helical peptides generated from a helix-loop-helix domain (residues 1-38 of cLZ) by nicking at leucine17. A third peptide consisting of an alpha-helix (residues 18-38) and a two-stranded beta-sheet (residues 39-56) structure was also identified. These peptides share structural motifs commonly found in different innate immune defenses. Functional cellular studies with outer membrane-, cytoplasmic membrane vitality- and redox-specific fluorescence dyes revealed that the lethal effect of the isolated antimicrobial peptides is due to membrane permeabilization and inhibition of redox-driven bacterial respiration. The results provide the first demonstration that pepsin can fine-tune the antimicrobial potency of cLZ by generating multiple antimicrobial peptide motifs, delineating a new molecular switch of cLZ in the mucosal defense systems. Finally, this finding offers a new strategy for the design of antibiotic peptide drugs with potential use in the treatment of infectious diseases.

Prebiotic effect of fructo-oligosaccharide supplemented term infant formula at two concentrations compared with unsupplemented formula and human milk

BACKGROUND

Human milk components, including oligosaccharides, affect the gastrointestinal flora of infants. Previous studies in adults have demonstrated that fructo-oligosaccharides increase potentially beneficial fecal bacteria, including bifidobacteria. The purpose of this study was to determine the prebiotic effect of infant formula supplemented with fructo-oligosaccharides.

METHODS

Healthy term infants 2 to 6 weeks of age were enrolled in a 5-week, prospective, randomized, crossover, single-site study with a nonrandomized human milk comparator group. Washout weeks preceded and followed a week of feeding with fructo-oligosaccharide-supplemented formula (1.5 or 3.0 g/L). Stool specimens were quantitatively cultured weekly for bacteroides, lactobacilli, bifidobacteria, clostridia and enterococci and were tested for Clostridium difficile toxin.

RESULTS

Seventy-two of 87 infants completed the trial; 58 were formula fed and 14 were human milk fed. Mean counts of bifidobacteria and lactobacilli were similar in all groups at entry and no group experienced a significant change in counts with fructo-oligosaccharide supplementation. After 7 days of fructo-oligosaccharide supplementation the bifidobacteria counts were greater in the 1.5 g/L fructo-oligosaccharide formula group than in the human milk fed or 3.0 g/L fructo-oligosaccharide formula groups. Formula-fed infants had higher counts of enterococci and bacteroides before fructo-oligosaccharide supplementation, and these counts did not change after supplementation. Clostridium counts increased 7 days after supplementation in the 1.5 g/L fructo-oligosaccharide formula group (P = 0.0356). No human milk fed infants had C. difficile toxin in stools. Fructo-oligosaccharide (3.0 g/L) supplementation resulted in more frequent and significantly softer stools.

CONCLUSIONS

Infant formula supplemented with 1.5 or 3.0 g/L fructo-oligosaccharides was safe but had minimal effect on fecal flora and C. difficile toxin.

Intestinal adherent bacteria and bacterial translocation in breast-fed and formula-fed rats in relation to susceptibility to infection

The barrier function of the intestinal mucosa is immature in the newborn mammal, and is strengthened by breast milk. We investigated this effect of breast milk by comparing the susceptibility to infection assessed in terms of adherent bacterial colonization of the intestinal tissue (AdC) and bacterial translocation (BT) between breast-fed and formula-fed newborn rats. Three-day-old rat pups were assigned to one of three groups: mother-reared (MR), pseudo-cannulated (sham), and artificially reared (AR). AR rats were infused with formula through an intragastric cannula, under the control of a computer-regulated pumping machine. MR and sham rat pups were reared with their respective dams and received breast milk until weaning in a specially designed cage. In 10-d-old rats, there was no significant difference in the fecal or cecal flora between the AR and MR groups, whereas the AdC and the BT to the liver were greater in the AR than MR group. Enterobacteriaceae, Streptococcus and/or Enterococcus, and Staphylococcus were dominantly detected as microorganisms in AdC flora and BT. The AdC flora did not directly reflect the bacterial colonization flora. These findings suggest that AR rat pups mature normally, although there is a greater colonization of Enterobacteriaceae and BT in AR than MR pups. Consequently, the intestinal barrier function of the pups reared by artificial feeding may become susceptible to BT, and AdC may be more indicative than bacterial colonization of the susceptibility to BT.