The intestinal microbiome and necrotizing enterocolitis

Red Blood Cell Transfusion, Anemia, Feeding, and the Risk of Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is a leading cause of morbidity and mortality in preterm infants. Severe anemia and red blood cell (RBC) transfusion are associated with gut inflammation and injury in preclinical models and observational studies. However, there is uncertainty about the causal role of these factors in the pathogenesis of NEC. Observational studies have shown that withholding feeding during RBC transfusion may reduce the risk of NEC, although confirmatory data from randomized trials are lacking. In this review, we summarize data on feeding during RBC transfusion and its role in NEC and highlight ongoing randomized trials.

The Detrimental Effects of Peripartum Antibiotics on Gut Proliferation and Formula Feeding Injury in Neonatal Mice Are Alleviated with Lactobacillus rhamnosus GG

Peripartum antibiotics can negatively impact the developing gut microbiome and are associated with necrotizing enterocolitis (NEC). The mechanisms by which peripartum antibiotics increase the risk of NEC and strategies that can help mitigate this risk remain poorly understood. In this study, we determined mechanisms by which peripartum antibiotics increase neonatal gut injury and evaluated whether probiotics protect against gut injury potentiated by peripartum antibiotics. To accomplish this objective, we administered broad-spectrum antibiotics or sterile water to pregnant C57BL6 mice and induced neonatal gut injury to their pups with formula feeding. We found that pups exposed to antibiotics had reduced villus height, crypt depth, and intestinal olfactomedin 4 and proliferating cell nuclear antigen compared to the controls, indicating that peripartum antibiotics impaired intestinal proliferation. When formula feeding was used to induce NEC-like injury, more severe intestinal injury and apoptosis were observed in the pups exposed to antibiotics compared to the controls. Supplementation with the probiotic Lactobacillus rhamnosus GG (LGG) reduced the severity of formula-induced gut injury potentiated by antibiotics. Increased intestinal proliferating cell nuclear antigen and activation of the Gpr81-Wnt pathway were noted in the pups supplemented with LGG, suggesting partial restoration of intestinal proliferation by probiotics. We conclude that peripartum antibiotics potentiate neonatal gut injury by inhibiting intestinal proliferation. LGG supplementation decreases gut injury by activating the Gpr81-Wnt pathway and restoring intestinal proliferation impaired by peripartum antibiotics. Our results suggest that postnatal probiotics may be effective in mitigating the increased risk of NEC associated with peripartum antibiotic exposure in preterm infants.

Particular genomic and virulence traits associated with preterm infant-derived toxigenic Clostridium perfringens strains

Clostridium perfringens is an anaerobic toxin-producing bacterium associated with intestinal diseases, particularly in neonatal humans and animals. Infant gut microbiome studies have recently indicated a link between C. perfringens and the preterm infant disease necrotizing enterocolitis (NEC), with specific NEC cases associated with overabundant C. perfringens termed C. perfringens-associated NEC (CPA-NEC). In the present study, we carried out whole-genome sequencing of 272 C. perfringens isolates from 70 infants across 5 hospitals in the United Kingdom. In this retrospective analysis, we performed in-depth genomic analyses (virulence profiling, strain tracking and plasmid analysis) and experimentally characterized pathogenic traits of 31 strains, including 4 from CPA-NEC patients. We found that the gene encoding toxin perfringolysin O, pfoA, was largely deficient in a human-derived hypovirulent lineage, as well as certain colonization factors, in contrast to typical pfoA-encoding virulent lineages. We determined that infant-associated pfoA+ strains caused significantly more cellular damage than pfoA- strains in vitro, and further confirmed this virulence trait in vivo using an oral-challenge C57BL/6 murine model. These findings suggest both the importance of pfoA+ C. perfringens as a gut pathogen in preterm infants and areas for further investigation, including potential intervention and therapeutic strategies.

Antenatal and Postnatal Sequelae of Oxidative Stress in Preterm Infants: A Narrative Review Targeting Pathophysiological Mechanisms

The detrimental effects of oxidative stress (OS) can start as early as after conception. A growing body of evidence has shown the pivotal role of OS in the development of several pathological conditions during the neonatal period, which have been therefore defined as OS-related neonatal diseases. Due to the physiological immaturity of their antioxidant defenses and to the enhanced antenatal and postnatal exposure to free radicals, preterm infants are particularly susceptible to oxidative damage, and several pathophysiological cascades involved in the development of prematurity-related complications are tightly related to OS. This narrative review aims to provide a detailed overview of the OS-related pathophysiological mechanisms that contribute to the main OS-related diseases during pregnancy and in the early postnatal period in the preterm population. Particularly, focus has been placed on pregnancy disorders typically associated with iatrogenic or spontaneous preterm birth, such as intrauterine growth restriction, pre-eclampsia, gestational diabetes, chorioamnionitis, and on specific postnatal complications for which the role of OS has been largely ascertained (e.g., respiratory distress, bronchopulmonary dysplasia, retinopathy of prematurity, periventricular leukomalacia, necrotizing enterocolitis, neonatal sepsis). Knowledge of the underlying pathophysiological mechanisms may increase awareness on potential strategies aimed at preventing the development of these conditions or at reducing the ensuing clinical burden.

Antibacterial and anti-inflammatory effects of Lactobacillus reuteri in its biofilm state contribute to its beneficial effects in a rat model of experimental necrotizing enterocolitis

INTRODUCTION

Necrotizing enterocolitis (NEC) remains a significant surgical emergency in neonates. We have demonstrated the efficacy of Lactobacillus reuteri (Lr) in protecting against experimental NEC when administered as a biofilm by incubation with maltose loaded dextranomer microspheres. Lr possesses antimicrobial and anti-inflammatory properties. We developed mutant strains of Lr to examine the importance of its antimicrobial and anti-inflammatory properties in protecting the intestines from NEC.

METHODS

Premature rat pups were exposed to hypoxia/hypothermia/hypertonic feeds to induce NEC. To examine the importance of antimicrobial reuterin and anti-inflammatory histamine, pups received either native or mutant forms of Lr, in either its planktonic or biofilm states, prior to induction of NEC. Intestinal histology was examined upon sacrifice.

RESULTS

Compared to no treatment, administration of a single dose of Lr in its biofilm state significantly decreased the incidence of NEC (67% vs. 18%, p < 0.0001), whereas Lr in its planktonic state had no significant effect. Administration of reuterin-deficient or histamine-deficient forms of Lr, in either planktonic or biofilm states, resulted in significant loss of efficacy.

CONCLUSION

Antimicrobial and anti-inflammatory effects of Lr contribute to its beneficial effects against NEC. This suggests that both infectious and inflammatory components contribute to the etiology of NEC.

A mini-review of advances in intestinal flora and necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a digestive disease that frequently occurs in premature infants with low gestational age and low birth weight, and seriously threatens the life of NEC patients. NEC pathogenesis is recognized to be affected by multiple factors, such as preterm birth, formula feeding, and low birth weight. As a popular object for the past decades, intestinal flora is commonly used in NEC-related studies, and intestinal disorder is considered as a critical risk factor for the occurrence and development of NEC. The colonization of abnormal microbiota into gastrointestinal micro-ecosystem can easily lead to the damage of intestinal mucosal barrier, destruction of immune function, inflammatory reaction, and further the occurrence of NEC. Although it is a low-cost and safe way to prevent and treat the NEC by early intervention of oral probiotics to regulate the intestinal homeostasis, more studies in the future are still encouraged to narrow the gap between theoretical guidance and practical application.

Dynamic Associations of Milk Components With the Infant Gut Microbiome and Fecal Metabolites in a Mother-Infant Model by Microbiome, NMR Metabolomic, and Time-Series Clustering Analyses

Background: The gut microbiome and fecal metabolites of breastfed infants changes during lactation, and are influenced by breast milk components. This study aimed to investigate dynamic associations of milk components with the infant gut microbiome and fecal metabolites throughout the lactation period in a mother–infant model.

Methods: One month after delivery, breast milk and subsequent infant feces were collected in a pair for 5 months from a mother and an exclusively breastfed infant. Composition of the fecal microbiome was determined with 16S rRNA sequencing. Low-molecular-weight metabolites, including human milk oligosaccharides (HMOs), and antibacterial proteins were measured in feces and milk using ¹H NMR metabolomics and enzyme-linked immunosorbent assays. The association of milk bioactive components with the infant gut microbiome and fecal metabolites was determined with Python clustering and correlation analyses.

Results: The HMOs in milk did not fluctuate throughout the lactation period. However, they began to disappear in infant feces at the beginning of month 4. Notably, at this time-point, a bifidobacterium species switching (from B. breve to B. longum subsp. infantis) occurred, accompanied by fluctuations in several metabolites including acetate and butyrate in infant feces.

Conclusions: Milk bioactive components, such as HMOs, might play different roles in the exclusively breastfed infants depending on the lactation period.

Necrotizing enterocolitis: Bench to bedside approaches and advancing our understanding of disease pathogenesis

Necrotizing enterocolitis (NEC) is a devastating, multifactorial disease mainly affecting the intestine of premature infants. Recent discoveries have significantly enhanced our understanding of risk factors, as well as, cellular and genetic mechanisms of this complex disease. Despite these advancements, no essential, single risk factor, nor the mechanism by which each risk factor affects NEC has been elucidated. Nonetheless, recent research indicates that maternal factors, antibiotic exposure, feeding, hypoxia, and altered gut microbiota pose a threat to the underdeveloped immunity of preterm infants. Here we review predisposing factors, status of unwarranted immune responses, and microbial pathogenesis in NEC based on currently available scientific evidence. We additionally discuss novel techniques and models used to study NEC and how this research translates from the bench to the bedside into potential treatment strategies.

Unraveling the Microbiome of Necrotizing Enterocolitis: Insights in Novel Microbial and Metabolomic Biomarkers

Necrotizing enterocolitis (NEC) is among the most relevant gastrointestinal diseases affecting mostly prematurely born infants with low birth weight. While intestinal dysbiosis has been proposed as one of the possible factors involved in NEC pathogenesis, the role of the gut microbiota remains poorly understood. In this study, the gut microbiota of preterm infants was explored to highlight differences in the composition between infants affected by NEC and infants prior to NEC development. A large-scale gut microbiome analysis was performed, including 47 shotgun sequencing data sets generated in the framework of this study, along with 124 retrieved from publicly available repositories. Meta-analysis led to the identification of preterm community state types (PT-CSTs), which recur in healthy controls and NEC infants. Such analyses revealed an overgrowth of a range of opportunistic microbial species accompanying the loss of gut microbial biodiversity in NEC subjects. Moreover, longitudinal insights into preterm infants prior to NEC development indicated Clostridium neonatale and Clostridium perfringens species as potential biomarkers for predictive early diagnosis of this disease. Furthermore, functional investigation of the enzymatic reaction profiles associated with pre-NEC condition suggested DL-lactate as a putative metabolic biomarker for early detection of NEC onset.

IMPORTANCE Necrotizing enterocolitis (NEC) is a severe gastrointestinal disease occurring predominantly in premature infants whose etiology is still not fully understood. In this study, the analysis of infant fecal samples through shotgun metagenomics approaches revealed a marked reduction of the intestinal (bio)diversity and an overgrowth of (opportunistic) pathogens associated with the NEC development. In particular, dissection of the infant’s gut microbiome before NEC diagnosis highlighted the potential involvement of Clostridium genus members in the progression of NEC. Remarkably, our analyses highlighted a gastrointestinal DL-lactate accumulation among NEC patients that might represent a novel potential functional biomarker for the early diagnosis of NEC.

Nutritional Management and Recommendation for Preterm Infants: A Narrative Review

Background: Preterm birth is defined as birth before 37 completed weeks of pregnancy. It is the most important predictor of adverse health and development infant outcomes that extend into the early childhood and beyond. It is also the leading cause of childhood mortality under 5 years of age worldwide and responsible for approximately one million neonatal deaths. It is also a significant contributor to childhood morbidities, with many survivors are facing an increased risk of lifelong disability and poor quality of life. Purpose: In this article, we aimed to describe features of preterm infants, what makes them different from term infants, and what to consider in nutritional management of preterm infants through a traditional narrative literature review. Discussion: Preterm infants are predisposed to more health complications than term infants with higher morbidity and mortality. This morbidity and mortality can be reduced through timely interventions for the mother and the preterm infant. Maternal interventions, such as health education and administration of micronutrient supplementation, are given before or during pregnancy and at delivery, whereas appropriate care for the preterm infants should be initiated immediately after birth, which include early breastfeeding and optimalization of weight gain. Conclusion: Essential care of the preterm infants and early aggressive nutrition should be provided to support rapid growth that is associated with improved neurodevelopmental outcomes. The goal is not only about survival but making sure that these preterm infants grow and develop without any residual morbidity.

Stress and corticotropin releasing factor (CRF) promote necrotizing enterocolitis in a formula-fed neonatal rat model

The etiology of necrotizing enterocolitis (NEC) is not known. Alterations in gut microbiome, mucosal barrier function, immune cell activation, and blood flow are characterized events in its development, with stress as a contributing factor. The hormone corticotropin-releasing factor (CRF) is a key mediator of stress responses and influences these aforementioned processes. CRF signaling is modulated by NEC's main risk factors of prematurity and formula feeding. Using an established neonatal rat model of NEC, we tested hypotheses that: (i) increased CRF levels-as seen during stress-promote NEC in formula-fed (FF) newborn rats, and (ii) antagonism of CRF action ameliorates NEC. Newborn pups were formula-fed to initiate gut inflammation and randomized to: no stress, no stress with subcutaneous CRF administration, stress (acute hypoxia followed by cold exposure-NEC model), or stress after pretreatment with the CRF peptide antagonist Astressin. Dam-fed unstressed and stressed littermates served as controls. NEC incidence and severity in the terminal ileum were determined using a histologic scoring system. Changes in CRF, CRF receptor (CRFRs), and toll-like receptor 4 (TLR4) expression levels were determined by immunofluorescence and immunoblotting, respectively. Stress exposure in FF neonates resulted in 40.0% NEC incidence, whereas exogenous CRF administration resulted in 51.7% NEC incidence compared to 8.7% in FF non-stressed neonates (p<0.001). Astressin prevented development of NEC in FF-stressed neonates (7.7% vs. 40.0%; p = 0.003). CRF and CRFR immunoreactivity increased in the ileum of neonates with NEC compared to dam-fed controls or FF unstressed pups. Immunoblotting confirmed increased TLR4 protein levels in FF stressed (NEC model) animals vs. controls, and Astressin treatment restored TLR4 to control levels. Peripheral CRF may serve as specific pharmacologic target for the prevention and treatment of NEC.

Prenatal Immunity and Influences on Necrotizing Enterocolitis and Associated Neonatal Disorders

Prior to birth, the neonate has limited exposure to pathogens. The transition from the intra-uterine to the postnatal environment initiates a series of complex interactions between the newborn host and a variety of potential pathogens that persist over the first few weeks of life. This transition is particularly complex in the case of the premature and very low birth weight infant, who may be susceptible to many disorders as a result of an immature and underdeveloped immune system. Chief amongst these disorders is necrotizing enterocolitis (NEC), an acute inflammatory disorder that leads to necrosis of the intestine, and which can affect multiple systems and have the potential to result in long term effects if the infant is to survive. Here, we examine what is known about the interplay of the immune system with the maternal uterine environment, microbes, nutritional and other factors in the pathogenesis of neonatal pathologies such as NEC, while also taking into consideration the effects on the long-term health of affected children.

Enteral Nutrition in Pediatric Short-Bowel Syndrome

Pediatric intestinal failure (IF) is the critical reduction of intestinal mass or function below the amount necessary for normal growth in children. Short-bowel syndrome (SBS) is the most common cause of IF in infants and children and is caused by intestinal resection. Enteral autonomy and freedom from parenteral nutrition is the mainstay of nutrition management in SBS. The goal is to achieve intestinal adaptation while maintaining proper growth and development. Treatment is variable, and there remains a paucity of evidence to draw well-informed conclusions for the care of individuals in this complex population. Physiological principles of enteral nutrition and practical recommendations for advancing the diet of patients with pediatric SBS are presented. Emerging trends in nutrition management, such as the growing interest in blending diets and the impact on SBS, are reviewed. Finally, the influence of the microbiome on enteral tolerance and small bowel bacterial overgrowth are considered.

The Neonatal Microbiome and Metagenomics: What Do We Know and What Is the Future?

The human microbiota includes the trillions of microorganisms living in the human body whereas the human microbiome includes the genes and gene products of this microbiota. Bacteria were historically largely considered to be pathogens that inevitably led to human disease. However, because of advances in both cultivation-based methods and the advent of metagenomics, bacteria are now recognized to be largely beneficial commensal organisms and thus, key to normal and healthy human development. This relatively new area of medical research has elucidated insights into diseases such as inflammatory bowel disease and obesity, as well as metabolic and atopic disorders. However, much remains unknown about the complexity of microbe-microbe and microbe-host interactions. Future efforts aimed at answering key questions pertaining to the early establishment of the microbiome, alongside what defines its dysbiosis, will likely lead to long-term health and mitigation of disease. Here, we review the relevant literature pertaining to modulations in the perinatal and neonatal microbiome, the impact of environmental and maternal factors in shaping the neonatal microbiome, and future questions and directions in the exciting emerging arena of metagenomic medicine.

Preterm neonatal immunology at the intestinal interface

Fetal and neonatal development represents a critical window for setting a path toward health throughout life. In this review, we focus on intestinal immunity, how it develops, and its implications for subsequent neonatal diseases. We discuss maternal nutritional and environmental exposures that dictate outcomes for the developing fetus. Although still controversial, there is evidence in support of an in utero microbiome. Specific well-intentioned and routine applications of antibiotics, steroids, and surgical interventions implemented before, during, and after birth skew the neonate towards pro-inflammatory dysbiosis. Shortly after birth, a consortium of maternal and environmentally derived bacteria, through cross-talk with the developing host immune system, takes center stage in developing or disrupting immune homeostasis at the intestinal interface. We also examine subsequent immunological cross-talks, which involve neonatal myeloid and lymphoid responses, and their potential impacts on health and disease such as necrotizing enterocolitis and sepsis, especially critical disease entities for the infant born preterm.

The Role of Glycosaminoglycans in Protection from Neonatal Necrotizing Enterocolitis: A Narrative Review

Necrotizing enterocolitis, a potentially fatal intestinal inflammatory disorder affecting primarily premature infants, is a significant cause of morbidity and mortality in neonates. While the etiology of the disease is, as yet, unknown, a number of risk factors for the development of necrotizing enterocolitis have been identified. One such risk factor, formula feeding, has been shown to contribute to both increased incidence and severity of the disease. The protective influences afforded by breastfeeding are likely attributable to the unique composition of human milk, an extremely potent, biologically active fluid. This review brings together knowledge on the pathogenesis of necrotizing enterocolitis and current thinking on the instrumental role of one of the more prominent classes of bioactive components in human breast milk, glycosaminoglycans.

Elevated Coefficient of Variation in Total Fecal Bile Acids Precedes Diagnosis of Necrotizing Enterocolitis

Accumulation of bile acids (BAs) may mediate development of necrotizing enterocolitis (NEC). Serial fecal samples were collected from premature infants with birth weight (BW) ≤ 1800 g, estimated gestational age (EGA) ≤ 32 weeks, and <30 days old prior to initiation of enteral feeding. Nine infants that developed Bell’s Stage ≥ II NEC were matched with control infants based on BW, EGA, day of life (DOL) enteral feeding was initiated and DOL of the first sample. From each subject, five samples matched by DOL collected were analyzed for BA levels and composition. Fifteen individual BA species were measured via LC-MS/MS and total BA levels were measured using the Diazyme Total Bile Acid Assay kit. No statistically significant differences in composition were observed between control and NEC at the level of individual species (p = 0.1133) or grouped BAs (p = 0.0742). However, there was a statistically significant difference (p = 0.000012) in the mean coefficient of variation (CV) between the two groups with infants developing NEC having more than four-fold higher mean CV than controls. Importantly, these variations occurred prior to NEC diagnosis. These data suggest fluctuations in total fecal BA levels could provide the basis for the first predictive clinical test for NEC.

Emerging Biomarkers for Prediction and Early Diagnosis of Necrotizing Enterocolitis in the Era of Metabolomics and Proteomics

Necrotizing Enterocolitis (NEC) is a catastrophic disease affecting predominantly premature infants and is characterized by high mortality and serious long-term consequences. Traditionally, diagnosis of NEC is based on clinical and radiological findings, which, however, are non-specific for NEC, thus confusing differential diagnosis of other conditions such as neonatal sepsis and spontaneous intestinal perforation. In addition, by the time clinical and radiological findings become apparent, NEC has already progressed to an advanced stage. During the last three decades, a lot of research has focused on the discovery of biomarkers, which could accurately predict and make an early diagnosis of NEC. Biomarkers used thus far in clinical practice include acute phase proteins, inflammation mediators, and molecules involved in the immune response. However, none has been proven accurate enough to predict and make an early diagnosis of NEC or discriminate clinical from surgical NEC or other non-NEC gastrointestinal diseases. Complexity of mechanisms involved in NEC pathogenesis, which remains largely poorly elucidated, could partly explain the unsatisfactory diagnostic performance of the existing NEC biomarkers. More recently applied technics can provide important insight into the pathophysiological mechanisms underlying NEC but can also aid the detection of potentially predictive, early diagnostic, and prognostic biomarkers. Progress in omics technology has allowed for the simultaneous measurement of a large number of proteins, metabolic products, lipids, and genes, using serum/plasma, urine, feces, tissues, and other biological specimens. This review is an update of current data on emerging NEC biomarkers detected using proteomics and metabolomics, further discussing limitations and future perspectives in prediction and early diagnosis of NEC.

The protective effects of fecal microbiota transplantation in an experimental model of necrotizing enterocolitis

BACKGROUND

Necrotizing enterocolitis (NEC) is a serious disease that affects premature neonates, causing high mortality. In the search for new options of treatment it was investigated whether fecal microbiota transplantation (FMT) decreased the inflammatory response during NEC development in experimental model.

METHODS

Wistar rats were used and divided as follows: naïve, control (NEC induction), FMT-before (transplantation of microbiota before insult) and FMT-after (microbiota transplantation after insult). The microbiota transplantation was performed by administering a feces solution obtained from an adult donor rat. The induction of enterocolitis involves feeding by artificial formula, hypothermia, hypoxia and endotoxin administration. MPO activity, TNF-α, IL-1β and IL-6 levels, oxidative and nitrosative damage and the grade of intestinal mucosa lesion were analyzed.

RESULTS

The control group had a significant increase of inflammatory and oxidative parameters when compared to naive animals. Both FMT-before and after decreased all inflammatory and oxidative damage parameters when compared to control group. This was also true to the intestinal mucosa damage.

CONCLUSION

FMT administered just before or after NEC induction improved gut and systemic inflammation, and gut oxidative damage and intestinal injury.

Curcumin and Intestinal Inflammatory Diseases: Molecular Mechanisms of Protection

Intestinal inflammatory diseases, such as Crohn’s disease, ulcerative colitis, and necrotizing enterocolitis, are becoming increasingly prevalent. While knowledge of the pathogenesis of these related diseases is currently incomplete, each of these conditions is thought to involve a dysfunctional, or overstated, host immunological response to both bacteria and dietary antigens, resulting in unchecked intestinal inflammation and, often, alterations in the intestinal microbiome. This inflammation can result in an impaired intestinal barrier allowing for bacterial translocation, potentially resulting in systemic inflammation and, in severe cases, sepsis. Chronic inflammation of this nature, in the case of inflammatory bowel disease, can even spur cancer growth in the longer-term. Recent research has indicated certain natural products with anti-inflammatory properties, such as curcumin, can help tame the inflammation involved in intestinal inflammatory diseases, thus improving intestinal barrier function, and potentially, clinical outcomes. In this review, we explore the potential therapeutic properties of curcumin on intestinal inflammatory diseases, including its antimicrobial and immunomodulatory properties, as well as its potential to alter the intestinal microbiome. Curcumin may play a significant role in intestinal inflammatory disease treatment in the future, particularly as an adjuvant therapy.

Metabolism of Milk Oligosaccharides in Preterm Pigs Sensitive to Necrotizing Enterocolitis

Human milk oligosaccharides (HMO) are major components of breast milk that may have local effects in the gastrointestinal tract and systemic functions after being absorbed, both depending on their metabolism. Using preterm pigs, we investigated the metabolic fate of HMO in three experiments with two different HMO blends. In addition, we examined effects on the colonic microbiota in the presence or absence of necrotizing enterocolitis (NEC). Thus, preterm pigs (n = 112) were fed formula without or with HMO supplementation (5-10) g/L of a mixture of 4 (4-HMO) or >25 HMO (25-HMO) for 5 (Experiment 1 and 2) or 11 days (Experiment 3). Individual HMO were quantified in colon contents and urine using MALDI-TOF-MS (matrix-assisted laser desorption ionization mass spectrometry) and HPAEC-PAD (high-performance anion-exchange chromatography with pulsed amperometric detection). Microbial colonization was analyzed by sequencing of 16S rRNA gene tags. Intestinal permeability was measured by lactulose to mannitol ratio in urine. HMO supplemented to formula were detected in urine and colon contents in preterm piglets after 5 and 11 days in all three experiments. The amount of HMO excreted via the gut or the kidneys showed large individual variations. Microbial diversity in the colon changed from high levels of Firmicutes (dominated by Clostridium) at day 5 (Exp 2) to high levels of Proteobacteria dominated by Helicobacter and Campylobacter at day 11 (Exp 3). Colonic microbiota composition as well as HMO excretion pattern varied greatly among piglets. Interestingly, the 5-day supplementation of the complex 25-HMO blend led to low concentrations of 3-fucosyllactose (FL) and lacto-N-fucopentaose (LNFP) I in colonic contents, indicating a preferred utilization of these two HMO. Although the interpretation of the data from our piglet study is difficult due to the large individual variation, the presence of Bifidobacteria, although low in total numbers, was correlated with total HMO contents, and specifically with 2'FL levels in colonic content. However, early supplementation of formula with HMO did not affect NEC incidence.

Associations between Red Blood Cell Transfusions and Necrotizing Enterocolitis in Very Low Birth Weight Infants: Ten-Year Data of a Tertiary Neonatal Unit

Background and Objective: Necrotizing enterocolitis (NEC) remains an important cause of mortality in preterm neonates. There are many risk factors for NEC; however, probably the most controversial one is red blood cell transfusions (RBCT). The data concerning the link between NEC and RBCT has been conflicting. Therefore, we aimed to analyze the association between NEC and RBCT in Neonatal Intensive Care Unit (NICU) at the Hospital of Lithuanian University of Health Sciences. Materials and Methods: We used the Very Low Birth Weight (VLBW) Infants database to match all infants with ≥2a Bell’s stage NEC admitted between 1 January 2005 and 31 December 2014 (n = 54) with a control group (n = 54) of similar gestational age and birth weight and without NEC. We analyzed the charts of these infants and performed statistical analysis on 20 clinical variables including RBCT. Results: The main clinical and demographic characteristics did not differ between the two groups. All variables associated with RBCT (receipt of any RBCT, the number of transfusions and the volume transfused in total) were significantly higher in the NEC group both before the onset of NEC and throughout the hospitalization. RBCT increased the odds of NEC even after adjustment for confounding factors. In addition, we found that congenital infection was more abundant in the NEC group and increased the odds of NEC 2.7 times (95% confidence interval CI (1.1, 6.3), p = 0.024). Conclusions: A higher number and the total volume of RBCT are associated with an increased risk of NEC in VLBW infants. The presence of congenital infection might identify the infants at risk.

New Nutritional and Therapeutical Strategies of NEC

Necrotizing enterocolitis (NEC) is an acquired severe disease of the digestive system affecting mostly premature babies, possibly fatal and frequently associated to systemic complications. Because of the severity of this condition and the possible long-term consequences on the child's development, many studies have aimed at preventing the occurrence of the primary events at the level of the bowel wall (ischemia and necrosis followed by sepsis) by modifying or manipulating the diet (breast milk versus formula) and/or the feeding pattern (time for initiation after birth, continuous versus bolus feeding, modulation of intake according clinical events). Feeding have been investigated so far in order to prevent NEC. However, currently well-established and shared clinical nutritional practices are not available in preventing NEC. Nutritional and surgical treatments of NEC are instead well defined. In selected cases surgery is a therapeutic option of NEC, requiring sometimes partial intestinal resection responsible for short bowel syndrome. In this paper we will investigate the available options for treating NEC according to the Walsh and Kliegman classification, focusing on feeding practices in managing short bowel syndrome that can complicate NEC. We will also analyze the proposed ways of preventing NEC.

Necrotizing enterocolitis: The intestinal microbiome, metabolome and inflammatory mediators

Necrotizing enterocolitis (NEC) is a disease of preterm infants and associated with significant mortality and morbidity. Although the pathogenesis of NEC is not clear, microbial dysbiosis, with a bloom of the phylum Proteobacteria, has been reported. Antibiotics and the use of H₂ blockers, which affect the gut microbiome, are associated with increased incidence of NEC. In association with dysbiosis, inflammatory processes are upregulated with increased Toll-like receptor signaling, leading to translocation of nuclear factor kappa-β, a transcription factor that induces transcription of various pro-inflammatory cytokines and chemokines. Microbial metabolites, short chain fatty acids including acetate and butyrate, may modulate immunity, inflammation, intestinal integrity and regulate transcription by epigenetic mechanisms. Evaluation of microbiome and metabolome may provide biomarkers for early diagnosis of NEC and microbial therapeutic approaches to correct microbial dysbiosis.

Enteral feeding composition and necrotizing enterocolitis

Enteral feeding and composition play a chief role in the prevention and treatment of necrotizing enterocolitis (NEC). In the face of decades of research on this fatal disease, the exact mechanism of disease is still poorly understood. There is established evidence that providing mother's own breast milk and standardization of feeding regimens leads to a decreased risk for NEC. More recent studies have focused on the provision of donor human milk or an exclusive human milk diet in the endeavor to prevent NEC while still maintaining adequate nutrition to the premature infant. There is growing literature on the provision of specific human milk components and its effect on the incidence of NEC.

Microbial Biomarkers of Intestinal Barrier Maturation in Preterm Infants

Intestinal barrier immaturity, or "leaky gut," is the proximate cause of susceptibility to necrotizing enterocolitis in preterm neonates. However, the impact of intestinal microbiota development on intestinal mucosal barrier maturation has not been evaluated in this population. In this study, we investigated a longitudinally sampled cohort of 38 preterm infants < 33 weeks gestation monitored for intestinal permeability (IP) and fecal microbiota during the first 2 weeks of life. Rapid decrease in IP indicating intestinal barrier function maturation correlated with significant increase in community diversity. In particular, members of the Clostridiales and Bifidobacterium were highly transcriptionally active, and progressively increasing abundance in Clostridiales was significantly associated with decreased intestinal permeability. Further, neonatal factors previously identified to promote intestinal barrier maturation, including early exclusive breastmilk feeding and shorter duration antibiotic exposure, associate with the early colonization of the intestinal microbiota by members of the Clostridiales, which altogether are associated with improved intestinal barrier function in preterm infants.

Intestinal microbiota in short bowel syndrome

Children with short bowel syndrome have significant changes to their intestinal microbiota after intestinal loss. The purpose of this article is to understand the potential implications of these changes on gut function, hepatic cholestasis and overall nutrition. Possible therapies to restore the commensal bacterial community in these patients will also be reviewed.

Oxidative Stress and Necrotizing Enterocolitis: Pathogenetic Mechanisms, Opportunities for Intervention, and Role of Human Milk

This review will examine the role of oxidative stress (OS) in the pathogenesis of necrotizing enterocolitis (NEC) and explore potential preventive and therapeutic antioxidant strategies. Preterm infants are particularly exposed to OS as a result of several perinatal stimuli and constitutive defective antioxidant defenses. For this reason, OS damage represents a contributing factor to several complications of prematurity, including necrotizing enterocolitis (NEC). Being NEC a multifactorial disease, OS may act as downstream component of the pathogenetic cascade. To counteract OS in preterm infants with NEC, several antioxidant strategies have been proposed and different antioxidant compounds have been experimented. It is well known that human milk (HM) is an important source of antioxidants. At the same time, the role of an exclusive HM diet is well recognized in the prevention of NEC. However, donor HM (DHM) processing may impair antioxidant properties. As DHM is becoming a common nutritional intervention for high risk PI, the antioxidant status of preterm and DHM and potential ways to preserve its antioxidant capacity may merit further investigation.

A randomised controlled trial of the probiotic Bifidobacterium breve BBG-001 in preterm babies to prevent sepsis, necrotising enterocolitis and death: the Probiotics in Preterm infantS (PiPS) trial

BACKGROUND

Necrotising enterocolitis (NEC) and late-onset sepsis remain important causes of death and morbidity in preterm babies. Probiotic administration might strengthen intestinal barrier function and provide protection; this is supported by published meta-analyses, but there is a lack of large well-designed trials.

OBJECTIVE

To test the use of the probiotic Bifidobacterium breve strain BBG-001 to prevent NEC, late-onset sepsis and death in preterm babies while monitoring probiotic colonisation of participants.

DESIGN

Double-blind, randomised, placebo-controlled trial.

SETTING

Recruitment was carried out in 24 hospitals, and the randomisation programme used a minimisation algorithm. Parents, clinicians and outcome assessors were blinded to the allocation.

PARTICIPANTS

Babies born between 23 and 30 weeks' gestation and randomised within 48 hours of birth. Exclusions included life-threatening or any gastrointestinal malformation detected within 48 hours of birth and no realistic chance of survival.

INTERVENTIONS

Active intervention: 1 ml of B. breve BBG-001 in one-eighth-strength infant formula Neocate(®) (Nutricia Ltd, Trowbridge, UK), (6.7 × 10(7) to 6.7 × 10(9) colony-forming units) per dose administered enterally. Placebo: 1 ml of one-eighth-strength infant formula Neocate. Started as soon as practicable and continued daily until 36 weeks' postmenstrual age.

MAIN OUTCOME MEASURES

Primary outcomes were an episode of bloodstream infection, with any organism other than a skin commensal, in any baby between 72 hours and 46 weeks' postmenstrual age; an episode of NEC Bell stage ≥ 2 in any baby; and death before discharge from hospital. Secondary outcomes included stool colonisation with B. breve.

RESULTS

In total, 654 babies were allocated to receive probiotic and 661 to receive placebo over 37 months from July 2010. Five babies were withdrawn; 650 babies from the probiotic group and 660 from the placebo group were included in the primary analysis. Baseline characteristics were well balanced. There was no evidence of benefit for the primary outcomes {sepsis: 11.2% vs. 11.7% [adjusted relative risk (RR) 0.97, 95% confidence interval (CI) 0.73 to 1.29]; NEC Bell stage ≥ 2: 9.4% vs. 10.0% [adjusted RR 0.93, 95% CI 0.68 to 1.27]; and death: 8.3% vs. 8.5% [adjusted RR 0.93, 95% CI 0.67 to 1.30]}. B. breve colonisation status was available for 1186 (94%) survivors at 2 weeks' postnatal age, of whom 724 (61%) were positive: 85% of the probiotic group and 37% of the placebo group. There were no differences for subgroup analyses by minimisation criteria and by stool colonisation with B. breve at 2 weeks. No harms associated with the interventions were reported.

LIMITATIONS

Cross-colonisation of the placebo arm could have reduced statistical power and confounded results; analyses suggest that this did not happen.

CONCLUSIONS

This is the largest trial to date of a probiotic intervention. It shows no evidence of benefit and does not support routine use of probiotics for preterm infants.

FUTURE WORK RECOMMENDATIONS

The increasing understanding of the pathogenesis of NEC and sepsis will inform the choice of probiotics for testing and better define the target population. Future Phase III trials should incorporate monitoring of the quality and viability of the intervention and colonisation rates of participants; cluster design should be considered.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN05511098 and EudraCT 2006-003445-17.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 20, No. 66. See the NIHR Journals Library website for further project information.

Necrotizing enterocolitis: Pathophysiology from a historical context

Necrotizing enterocolitis (NEC) continues to afflict approximately 7% of preterm infants born weighing less than 1500g, though recent investigations have provided novel insights into the pathogenesis of this complex disease. The disease has been a major cause of morbidity and mortality in neonatal intensive care units worldwide for many years, and our current understanding reflects exceptional observations made decades ago. In this review, we will describe NEC from a historical context and summarize seminal findings that underscore the importance of enteral feeding, the gut microbiota, and intestinal inflammation in this complex pathophysiology.

Preterm infants with necrotising enterocolitis demonstrate an unbalanced gut microbiota

AIM

This Lebanese study tested the hypothesis that differences would exist in the gut microbiota of preterm infants with and without necrotising enterocolitis (NEC), as reported in Western countries.

METHODS

This study compared 11 infants with NEC and 11 controls, all born at 27-35 weeks, in three neonatal intensive care units between January 2013 and March 2015. Faecal samples were collected at key time points, and microbiota was analysed by culture, quantitative PCR (qPCR) and temperature temporal gel electrophoresis (TTGE).

RESULTS

The cultures revealed that all preterm infants were poorly colonised and harboured no more than seven species. Prior to NEC diagnosis, significant differences were observed by qPCR with a higher colonisation by staphylococci (p = 0.034) and lower colonisations by enterococci (p = 0.039) and lactobacilli (p = 0.048) in the NEC group compared to the healthy controls. Throughout the study, virtually all of the infants were colonised by Enterobacteriaceae at high levels. TTGE analysis revealed no particular clusterisation, showing high interindividual variability.

CONCLUSION

The NEC infants were poorly colonised with no more than seven species, and the controls had a more diversified and balanced gut microbiota. Understanding NEC aetiology better could lead to more effective prophylactic interventions and a reduced incidence.

Probiotics Prevent Late-Onset Sepsis in Human Milk-Fed, Very Low Birth Weight Preterm Infants: Systematic Review and Meta-Analysis

Growing evidence supports the role of probiotics in reducing the risk of necrotizing enterocolitis, time to achieve full enteral feeding, and late-onset sepsis (LOS) in preterm infants. As reported for several neonatal clinical outcomes, recent data have suggested that nutrition might affect probiotics' efficacy. Nevertheless, the currently available literature does not explore the relationship between LOS prevention and type of feeding in preterm infants receiving probiotics. Thus, the aim of this systematic review and meta-analysis was to evaluate the effect of probiotics for LOS prevention in preterm infants according to type of feeding (exclusive human milk (HM) vs. exclusive formula or mixed feeding). Randomized-controlled trials involving preterm infants receiving probiotics and reporting on LOS were included in the systematic review. Only trials reporting on outcome according to feeding type were included in the meta-analysis. Fixed-effects models were used and random-effects models were used when significant heterogeneity was found. The results were expressed as risk ratio (RR) with 95% confidence interval (CI). Twenty-five studies were included in the meta-analysis. Overall, probiotic supplementation resulted in a significantly lower incidence of LOS (RR 0.79 (95% CI 0.71-0.88), p < 0.0001). According to feeding type, the beneficial effect of probiotics was confirmed only in exclusively HM-fed preterm infants (RR 0.75 (95% CI 0.65-0.86), p < 0.0001). Among HM-fed infants, only probiotic mixtures, and not single-strain products, were effective in reducing LOS incidence (RR 0.68 (95% CI 0.57-0.80) p < 0.00001). The results of the present meta-analysis show that probiotics reduce LOS incidence in exclusively HM-fed preterm infants. Further efforts are required to clarify the relationship between probiotics supplementation, HM, and feeding practices in preterm infants.

Supplementation with Lactobacillus paracasei or Pediococcus pentosaceus does not prevent diarrhoea in neonatal pigs infected with Escherichia coli F18

Infectious diarrhoea is a worldwide problem in newborns. Optimal bacterial colonisation may enhance gut maturation and protect against pathogenic bacteria after birth. We hypothesised that lactic acid bacteria (LAB) administration prevents pathogen-induced diarrhoea in formula-fed newborns. Newborn caesarean-delivered, colostrum-deprived term piglets on parenteral nutrition for the first 15 h, were used as models for sensitive newborn infants. A commercially available probiotic strain, Lactobacillus paracasei F19 (LAP, 2·6×108 colony-forming units (CFU)/kg per d) and a novel LAB isolate, Pediococcus pentosaceus (PEP, 1·3×1010 CFU/kg per d), were administered for 5 d with or without inoculation of the porcine pathogen, Escherichia coli F18 (F18, 1010 CFU/d). This resulted in six treatment groups: Controls (n 9), LAP (n 10), PEP (n 10), F18 (n 10), F18-LAP (n 10) and F18-PEP (n 10). The pathogen challenge increased diarrhoea and density of F18 in the intestinal mucosa (P<0·05). LAB supplementation further increased the diarrhoea score, relative to F18 alone (P<0·01). Intestinal structure and permeability were similar among groups, whereas brush border enzymes were affected in variable intestinal regions with decreased activities in most cases after F18 and LAB inoculation. Bacterial density in colon mucosa increased after F18 inoculation (P<0·05) but was unaffected by LAB supplementation. In colon contents, acetic and butyric acids were increased by PEP (P<0·05). The LAB used in this study failed to reduce E. coli-induced diarrhoea in sensitive newborn pigs. In vulnerable newborns there may be a delicate balance among bacterial composition and load, diet and the host. Caution may be required when administering LAB to compromised newborns suffering from enteric infections.

Improved outcomes for inborn babies with uncomplicated gastroschisis

INTRODUCTION

Gastroschisis (GS) is a common abdominal wall defect necessitating neonatal surgery and intensive care. We hypothesized that inborn patients had improved outcomes compared to patients born at an outside hospital (outborn) and transferred for definitive treatment.

METHODS

A single center, retrospective chart review at a pediatric tertiary care center was performed from 2010 to 2015. All patients whose primary surgical treatment of GS was performed at this center were included. We compared patients delivered within our center (inborn) to patients delivered outside of our center and transferred for surgical care (outborn). Babies with complicated gastroschisis were excluded.

RESULTS

During the study period 79 patients with GS were identified. Of these, 53 were inborn and 26 were outborn. Sixteen patients were excluded for complicated GS. The rate of complicated GS was higher in the outborn group (32%) compared to the inborn population (11%) (p=0.03). Duration of stay, readmission rate and time on TPN were all significantly decreased for inborn patients, while time to definitive closure was similar. Mortality was 0% for both inborn and outborn patients.

CONCLUSION

Patients with uncomplicated GS seem to benefit from delivery with immediate pediatric surgical care available eliminating the need for transfer.

LEVEL OF EVIDENCE

III.

Intestinal dysbiosis in preterm infants preceding necrotizing enterocolitis: a systematic review and meta-analysis

BACKGROUND

Necrotizing enterocolitis (NEC) is a catastrophic disease of preterm infants, and microbial dysbiosis has been implicated in its pathogenesis. Studies evaluating the microbiome in NEC and preterm infants lack power and have reported inconsistent results.

METHODS AND RESULTS

Our objectives were to perform a systematic review and meta-analyses of stool microbiome profiles in preterm infants to discern and describe microbial dysbiosis prior to the onset of NEC and to explore heterogeneity among studies. We searched MEDLINE, PubMed, CINAHL, and conference abstracts from the proceedings of Pediatric Academic Societies and reference lists of relevant identified articles in April 2016. Studies comparing the intestinal microbiome in preterm infants who developed NEC to those of controls, using culture-independent molecular techniques and reported α and β-diversity metrics, and microbial profiles were included. In addition, 16S ribosomal ribonucleic acid (rRNA) sequence data with clinical meta-data were requested from the authors of included studies or searched in public data repositories. We reprocessed the 16S rRNA sequence data through a uniform analysis pipeline, which were then synthesized by meta-analysis. We included 14 studies in this review, and data from eight studies were available for quantitative synthesis (106 NEC cases, 278 controls, 2944 samples). The age of NEC onset was at a mean ± SD of 30.1 ± 2.4 weeks post-conception (n = 61). Fecal microbiome from preterm infants with NEC had increased relative abundances of Proteobacteria and decreased relative abundances of Firmicutes and Bacteroidetes prior to NEC onset. Alpha- or beta-diversity indices in preterm infants with NEC were not consistently different from controls, but we found differences in taxonomic profiles related to antibiotic exposure, formula feeding, and mode of delivery. Exploring heterogeneity revealed differences in microbial profiles by study and the target region of the 16S rRNA gene (V1-V3 or V3-V5).

CONCLUSIONS

Microbial dysbiosis preceding NEC in preterm infants is characterized by increased relative abundances of Proteobacteria and decreased relative abundances of Firmicutes and Bacteroidetes. Microbiome optimization may provide a novel strategy for preventing NEC.

Pathogenesis of NEC: Impact of an altered intestinal microbiome

Necrotizing enterocolitis (NEC), a disease most commonly seen in preterm infants, often presents without warning and is associated with very high mortality and morbidity. Progress in the prevention and treatment of NEC has been slow. In this article, we will discuss some of the reasons as to why this progress has been slow. We will describe some of the factors that appear to be highly associated and important components in the pathophysiology of NEC. We will discuss the intestinal microbial environment of the fetus as well as the preterm infant and how interaction of dysbiosis with an immature gastrointestinal tract combined with dietary factors play a role in the pathogenesis of NEC. Testable hypotheses are discussed as well as how these may lead to not only a better understanding of the pathophysiology of the disease but also the preventative strategies.

The Role of Mucosal Immunity in the Pathogenesis of Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is the most devastating gastrointestinal disease of prematurity. Although the precise cause is not well understood, the main risk factors thought to contribute to NEC include prematurity, formula feeding, and bacterial colonization. Recent evidence suggests that NEC develops as a consequence of intestinal hyper-responsiveness to microbial ligands upon bacterial colonization in the preterm infant, initiating a cascade of aberrant signaling events, and a robust pro-inflammatory mucosal immune response. We now have a greater understanding of important mechanisms of disease pathogenesis, such as the role of cytokines, immunoglobulins, and immune cells in NEC. In this review, we will provide an overview of the mucosal immunity of the intestine and the relationship between components of the mucosal immune system involved in the pathogenesis of NEC, while highlighting recent advances in the field that have promise as potential therapeutic targets. First, we will describe the cellular components of the intestinal epithelium and mucosal immune system and their relationship to NEC. We will then discuss the relationship between the gut microbiota and cell signaling that underpins disease pathogenesis. We will conclude our discussion by highlighting notable therapeutic advancements in NEC that target the intestinal mucosal immunity.

Necrotizing enterocolitis: new insights into pathogenesis and mechanisms

Necrotizing enterocolitis (NEC) is the most frequent and lethal disease of the gastrointestinal tract of preterm infants. At present, NEC is thought to develop in the premature host in the setting of bacterial colonization, often after administration of non-breast milk feeds, and disease onset is thought to be due in part to a baseline increased reactivity of the premature intestinal mucosa to microbial ligands as compared with the full-term intestinal mucosa. The increased reactivity leads to mucosal destruction and impaired mesenteric perfusion and partly reflects an increased expression of the bacterial receptor Toll-like receptor 4 (TLR4) in the premature gut, as well as other factors that predispose the intestine to a hyper-reactive state in response to colonizing microorganisms. The increased expression of TLR4 in the premature gut reflects a surprising role for this molecule in the regulation of normal intestinal development through its effects on the Notch signalling pathway. This Review will examine the current approach to the diagnosis and treatment of NEC, provide an overview of our current knowledge regarding its molecular underpinnings and highlight advances made within the past decade towards the development of specific preventive and treatment strategies for this devastating disease.

Manipulation of the Microbiota Using Probiotics

A number of diseases are associated with alterations in the composition of the microbiota of various niches of the human body. Although, in most cases, it is unclear if these alterations are the cause or the consequence of disease, they provide a rationale for therapeutic or prophylactic manipulation of a dysbiotic microbiota. Approaches to manipulate the microbiome include administration of either live bacteria, which are underrepresented in the diseased individual, substances that aim at increasing the populations of these bacteria, or a combination of the two. This chapter summarizes the available data in therapeutic manipulation of a various diseased states including irritable bowel syndrome, inflammatory bowel disease, necrotizing enterocolitis, atopic and allergic diseases, and antibiotic-associated and infectious diarrhoea.

Probiotics and Time to Achieve Full Enteral Feeding in Human Milk-Fed and Formula-Fed Preterm Infants: Systematic Review and Meta-Analysis

Probiotics have been linked to a reduction in the incidence of necrotizing enterocolitis and late-onset sepsis in preterm infants. Recently, probiotics have also proved to reduce time to achieve full enteral feeding (FEF). However, the relationship between FEF achievement and type of feeding in infants treated with probiotics has not been explored yet. The aim of this systematic review and meta-analysis was to evaluate the effect of probiotics in reducing time to achieve FEF in preterm infants, according to type of feeding (exclusive human milk (HM) vs. formula). Randomized-controlled trials involving preterm infants receiving probiotics, and reporting on time to reach FEF were included in the systematic review. Trials reporting on outcome according to type of feeding (exclusive HM vs. formula) were included in the meta-analysis. Fixed-effect or random-effects models were used as appropriate. Results were expressed as mean difference (MD) with 95% confidence interval (CI). Twenty-five studies were included in the systematic review. In the five studies recruiting exclusively HM-fed preterm infants, those treated with probiotics reached FEF approximately 3 days before controls (MD -3.15 days (95% CI -5.25/-1.05), p = 0.003). None of the two studies reporting on exclusively formula-fed infants showed any difference between infants receiving probiotics and controls in terms of FEF achievement. The limited number of included studies did not allow testing for other subgroup differences between HM and formula-fed infants. However, if confirmed in further studies, the 3-days reduction in time to achieve FEF in exclusively HM-fed preterm infants might have significant implications for their clinical management.

Evidence for persistent and shared bacterial strains against a background of largely unique gut colonization in hospitalized premature infants

The potentially critical stage of initial gut colonization in premature infants occurs in the hospital environment, where infants are exposed to a variety of hospital-associated bacteria. Because few studies of microbial communities are strain-resolved, we know little about the extent to which specific strains persist in the hospital environment and disperse among infants. To study this, we compared 304 near-complete genomes reconstructed from fecal samples of 21 infants hospitalized in the same intensive care unit in two cohorts, over 3 years apart. The genomes represent 159 distinct bacterial strains, only 14 of which occurred in multiple infants. Enterococcus faecalis and Staphylococcus epidermidis, common infant gut colonists, exhibit diversity comparable to that of reference strains, inline with introduction of strains from infant-specific sources rather than a hospital strain pool. Unlike other infants, a pair of sibling infants shared multiple strains, even after extensive antibiotic administration, suggesting overlapping strain-sources and/or genetic selection drive microbiota similarities. Interestingly, however, five strains were detected in infants hospitalized three years apart. Three of these were also detected in multiple infants in the same year. This finding of a few widely dispersed and persistent bacterial colonizers despite overall low potential for strain dispersal among infants has implications for understanding and directing healthy colonization.

Etiology and medical management of NEC

Necrotising enterocolitis (NEC) is a serious infection of the bowel that predominantly affects preterm infants and is a leading cause for mortality and morbidity in preterm infants. It involves a spectrum of pathology including widespread inflammation of the intestinal mucosa, invasion of the immature gut by enteric gas forming bacteria, dissection of the gut wall and portal veins by this gas, often culminating in ischemic necrosis of the intestine. This article provides an overview of the incidence, etio-pathological risk factors, preventive strategies and medical management of NEC.

Harvesting the benefits of biofilms: A novel probiotic delivery system for the prevention of necrotizing enterocolitis

BACKGROUND/PURPOSE

Probiotics reduce the incidence of necrotizing enterocolitis (NEC) albeit only when administered at high frequency (at least daily). We have developed a novel probiotic delivery system in which probiotics are grown as a biofilm on microspheres, allowing enhanced efficacy with only a single treatment.

METHODS

Neonatal rats were subjected to experimental NEC. Pups received a single enteral dose of: (1) vehicle only, (2) unloaded microspheres, (3) MRS (broth)-loaded microspheres, (4) Lactobacillus reuteri, (5) L. reuteri grown on unloaded microspheres, or (6) L. reuteri grown on MRS-loaded microspheres. Intestinal injury was graded histologically and intestinal permeability determined by serum levels of enterally administered fluorescein isothiocyanate-labeled dextran.

RESULTS

69% of untreated pups developed NEC, whereas 32% of pups treated with L. reuteri grown as a biofilm on unloaded microspheres (p=0.009) and 33% of pups treated with L. reuteri grown as a biofilm on MRS-loaded microspheres (p=0.005) developed NEC. No other group had a significant reduction in NEC. Furthermore, pups treated with L. reuteri grown as a biofilm had significantly reduced intestinal permeability.

CONCLUSIONS

A single dose of Lactobacillus biofilm grown on biocompatible microspheres significantly reduces NEC incidence and severity. This novel probiotic delivery system may be beneficial in the prevention of NEC in the future.

Roles of nitric oxide and intestinal microbiota in the pathogenesis of necrotizing enterocolitis

Necrotizing enterocolitis remains one of the most vexing problems in the neonatal intensive care unit. Risk factors for NEC include prematurity, formula feeding, and inappropriate microbial colonization of the GI tract. The pathogenesis of NEC is believed to involve weakening of the intestinal barrier by perinatal insults, translocation of luminal bacteria across the weakened barrier, an exuberant inflammatory response, and exacerbation of the barrier damage by inflammatory factors, leading to a vicious cycle of inflammation-inflicted epithelial damage. Nitric oxide (NO), produced by inducible NO synthase (iNOS) and reactive NO oxidation intermediates play a prominent role in the intestinal barrier damage by inducing enterocyte apoptosis and inhibiting the epithelial restitution processes, namely enterocyte proliferation and migration. The factors that govern iNOS upregulation in the intestine are not well understood, which hampers efforts in developing NO/iNOS-targeted therapies. Similarly, efforts to identify bacteria or bacterial colonization patterns associated with NEC have met with limited success, because the same bacterial species can be found in NEC and in non-NEC subjects. However, microbiome studies have identified the three important characteristics of early bacterial populations of the GI tract: high diversity, low complexity, and fluidity. Whether NEC is caused by specific bacteria remains a matter of debate, but data from hospital outbreaks of NEC strongly argue in favor of the infectious nature of this disease. Studies in Cronobacter muytjensii have established that the ability to induce NEC is the property of specific strains rather than the species as a whole. Progress in our understanding of the roles of bacteria in NEC will require microbiological experiments and genome-wide analysis of virulence factors.

An Integrated Review of Intestinal Microbiota in the Very Premature Infant

BACKGROUND

The intestinal microbiota is important for optimal intestinal function and protection against infection. Disruption of the intestinal microbiota has been linked to necrotizing enterocolitis (NEC) and late-onset sepsis (LOS).

OBJECTIVES

To determine what is known about the intestinal microbiota of very premature infants. We describe the relationship of the intestinal microbiota to NEC and LOS and provide an overview of the effect of environmental factors.

METHODS

A review was conducted using PubMed/MEDLINE from 2008 to 2015 to examine what is currently known about the intestinal microbiota of very premature infants.

DISCUSSION

The intestinal bacteria are low in diversity and generally contain a predominance of potentially pathogenic bacteria. Evidence suggests that these bacteria play a role in NEC as well as LOS through translocation. Environmental factors such as mode of delivery, use of antibiotics, and type of feeding may also contribute to the development of the intestinal microbiota.

Cluster of late preterm and term neonates with necrotizing enterocolitis symptomatology: descriptive and case-control study

OBJECTIVE

To investigate a necrotizing enterocolitis (NEC) cluster of late preterm and term neonates (gestational age ≥34 weeks).

METHODS

We conducted a descriptive and a case-control study. Medical records of neonates with modified Bell stage ≥ IB NEC and matched controls were reviewed, in addition to microbiological and environmental investigation. Study variables included maternal/delivery and neonatal factors, medications, procedures and feeding practices. Univariable/multivariable logistic regression analyses were performed for all and for stage ≥ II cases.

RESULTS

Out of 1841 late preterm and term neonates, 10 stage IB and 10 stage ≥ II [mean(SD) birthweight 2529.3 (493.04) g, gestational age 36.96 (1.48) weeks] presented with NEC symptomatology at mean 4.6 (range 2-8) days. Nearly all (19/20) resulted from high-risk pregnancies and received postpartum intermediate care. All were exclusively or partly formula fed. Most (14/20) were born by cesarean delivery. Eight underwent surgery, with no fatality. Intermediate care (p = 0.006), transient tachypnea (p = 0.049), not receiving breast milk (p = 0.019) and in addition intrauterine growth restriction (IUGR) (p = 0.017) for stage ≥ II cases were independently associated with NEC.

CONCLUSIONS

Late preterm and term neonates in need of intermediate care, with IUGR and transient tachypnea were susceptible to NEC; feeding with breast milk was an important protective factor.

Disruptions of the intestinal microbiome in necrotizing enterocolitis, short bowel syndrome, and Hirschsprung's associated enterocolitis

Next generation sequencing techniques are currently revealing novel insight into the microbiome of the human gut. This new area of research seems especially relevant for neonatal diseases, because the development of the intestinal microbiome already starts in the perinatal period and preterm infants with a still immature gut associated immune system may be harmed by a dysproportional microbial colonization. For most gastrointestinal diseases requiring pediatric surgery there is very limited information about the role of the intestinal microbiome. This review aims to summarize the current knowledge and outline future perspectives for important pathologies like necrotizing enterocolitis (NEC) of the newborn, short bowel syndrome (SBS), and Hirschsprung’s disease associated enterocolitis (HAEC). Only studies applying next generation sequencing techniques to analyze the diversity of the intestinal microbiome were included. In NEC patients intestinal dysbiosis could already be detected prior to any clinical evidence of the disease resulting in a reduction of the bacterial diversity. In SBS patients the diversity seems to be reduced compared to controls. In children with Hirschsprung’s disease the intestinal microbiome differs between those with and without episodes of enterocolitis. One common finding for all three diseases seems to be an overabundance of Proteobacteria. However, most human studies are based on fecal samples and experimental data question whether fecal samples actually represent the microbiome at the site of the diseased bowel and whether the luminal (transient) microbiome compares to the mucosal (resident) microbiome. In conclusion current studies already allow a preliminary understanding of the potential role of the intestinal microbiome in pediatric surgical diseases. Future investigations could clarify the interface between the intestinal epithelium, its immunological competence and mucosal microbiome. Advances in this field may have an impact on the understanding and non-operative treatment of such diseases in infancy.

The Role of Immunonutrients in the Prevention of Necrotizing Enterocolitis in Preterm Very Low Birth Weight Infants

Necrotizing enterocolitis (NEC) is a critical intestinal emergency condition, which mainly occurs in preterm very low birth weight (PVLBW) infants. Despite remarkable advances in the care of PVLBW infants, with considerable improvement of the survival rate in recent decades, the incidence of NEC and NEC-related mortality have not declined accordingly. The fast progression from nonspecific signs to extensive necrosis also makes primary prevention the first priority. Recently, increasing evidence has indicated the important role of several nutrients in primary prevention of NEC. Therefore, the aim of this review is to summarize some potential immunomodulatory nutrients in the prevention of NEC, including bovine colostrum, probiotics, prebiotics (e.g., human milk oligosaccharides), long chain polyunsaturated fatty acids, and amino acids (glutamine, cysteine and N-acetylcysteine, l-arginine and l-citrulline). Based on current research evidence, probiotics are the most documented effective method to prevent NEC, while others still require further investigation in animal studies and clinical randomized controlled trials.

Blood Groups in Infection and Host Susceptibility

Blood group antigens represent polymorphic traits inherited among individuals and populations. At present, there are 34 recognized human blood groups and hundreds of individual blood group antigens and alleles. Differences in blood group antigen expression can increase or decrease host susceptibility to many infections. Blood groups can play a direct role in infection by serving as receptors and/or coreceptors for microorganisms, parasites, and viruses. In addition, many blood group antigens facilitate intracellular uptake, signal transduction, or adhesion through the organization of membrane microdomains. Several blood groups can modify the innate immune response to infection. Several distinct phenotypes associated with increased host resistance to malaria are overrepresented in populations living in areas where malaria is endemic, as a result of evolutionary pressures. Microorganisms can also stimulate antibodies against blood group antigens, including ABO, T, and Kell. Finally, there is a symbiotic relationship between blood group expression and maturation of the gastrointestinal microbiome.