Prevention of neonatal necrotizing enterocolitis

The Practice of Enteral Nutrition: Clinical Evidence for Feeding Protocols

Establishing full enteral nutrition in critically ill preterm infants with immature gastrointestinal function is challenging. In this article, we will summarize emerging clinical evidence from randomized clinical trials suggesting the feasibility and efficacy of feeding interventions targeting the early establishment of full enteral nutrition. We will also examine trial outcomes of higher volume feedings after the establishment of full enteral nutrition. Only data from randomized clinical trials will be discussed extensively. Future opportunities for clinical research will also be presented.

Impact of maternal factors, environmental factors, and race on necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a complex disease with a multifactorial etiology. As the leading cause of intestinal morbidity and mortality among premature infants, many resources are being dedicated to neonatal care and molecular targets in the newborn intestine. However, NEC is heavily influenced by maternal and perinatal factors as well. Given its nature, preventive approaches to NEC are more likely to improve outcomes than new treatment strategies. Therefore, this review focuses on maternal, environmental, and racial factors associated with the development of NEC, with an emphasis on those that may be modifiable to decrease the incidence of the disease.

Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is an inflammatory disease affecting premature infants. Intestinal microbial composition may play a key role in determining which infants are predisposed to NEC and when infants are at highest risk of developing NEC. It is unclear how to optimize antibiotic therapy in preterm infants to prevent NEC and how to optimize antibiotic regimens to treat neonates with NEC. This article discusses risk factors for NEC, how dysbiosis in preterm infants plays a role in the pathogenesis of NEC, and how probiotic and antibiotic therapy may be used to prevent and/or treat NEC and its sequelae.

Probiotics in the Prevention and Treatment of Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is a disease with high morbidity and mortality that occurs mainly in premature born infants. The pathophysiologic mechanisms indicate that gastrointestinal dysbiosis is a major risk factor. We searched for relevant articles published in PubMed and Google Scholar in the English language up to October 2020. Articles were extracted using subject headings and keywords of interest to the topic. Interesting references in included articles were also considered. Network meta-analysis suggests the preventive efficacy of Bifidobacterium and Lactobacillus spp., but even more for mixtures of Bifidobacterium, Streptococcus, and Bifidobacterium, and Streptococcus spp. However, studies comparing face-to-face different strains are lacking. Moreover, differences in inclusion criteria, dosage strains, and primary outcomes in most trials are major obstacles to providing evidence-based conclusions. Although adverse effects have not been reported in clinical trials, case series of adverse outcomes, mainly septicemia, have been published. Consequently, systematic administration of probiotic bacteria to prevent NEC is still debated in literature. The risk-benefit ratio depends on the incidence of NEC in a neonatal intensive care unit, and evidence has shown that preventive measures excluding probiotic administration can result in a decrease in NEC.

Optimizing Nutritional Strategies to Prevent Necrotizing Enterocolitis and Growth Failure after Bowel Resection

Necrotizing enterocolitis (NEC), the first cause of short bowel syndrome (SBS) in the neonate, is a serious neonatal gastrointestinal disease with an incidence of up to 11% in preterm newborns less than 1500 g of birth weight. The rate of severe NEC requiring surgery remains high, and it is estimated between 20–50%. Newborns who develop SBS need prolonged parenteral nutrition (PN), experience nutrient deficiency, failure to thrive and are at risk of neurodevelopmental impairment. Prevention of NEC is therefore mandatory to avoid SBS and its associated morbidities. In this regard, nutritional practices seem to play a key role in early life. Individualized medical and surgical therapies, as well as intestinal rehabilitation programs, are fundamental in the achievement of enteral autonomy in infants with acquired SBS. In this descriptive review, we describe the most recent evidence on nutritional practices to prevent NEC, the available tools to early detect it, the surgical management to limit bowel resection and the best nutrition to sustain growth and intestinal function.

Gastric Residual to Predict Necrotizing Enterocolitis in Preterm Piglets As Models for Infants

BACKGROUND

Necrotizing enterocolitis (NEC) is a serious intestinal inflammatory disease in preterm infants. High volume of gastric residual (GR) after oral feedings is often used as a predictor of NEC, but evidence is limited. Using NEC-sensitive preterm piglets as models, we hypothesized that GR mass and related plasma biomarkers predict early onset of NEC.

METHODS

In total, 258 newborn preterm piglets were fed bovine milk-based formulas for 5 days. At euthanasia, the stomach, small intestine, and colon were evaluated for NEC lesions. Mass, acidity, gastrin, and bile acid levels were determined for GR content, together with gastrin, glucagon-like peptide 2 (GLP-2), and gastric inhibitory polypeptide (GIP) levels in plasma.

RESULTS

In total, 48% of piglets had NEC lesions in the small intestine and/or colon. These piglets had higher GR mass (+32%, P < 0.001) and lower gastric bile acid concentrations (-22%, P < 0.05) than piglets without NEC lesions. The positive and negative predictive values for these markers were 34%-61%. Gastric acidity, gastrin, GLP-2, and GIP levels were similar for piglets with and without NEC lesions.

CONCLUSION

Elevated GR mass correlates positively with NEC lesions but may be a poor predictor of NEC, even when combined with other biomarkers. More knowledge about gastric emptying and gut transit in preterm neonates is required to understand how GR volume and composition relate to morbidities, such as NEC, in preterm neonates.

Probiotics and the prevention of necrotizing enterocolitis

BACKGROUND

Immaturity of the host immune system and alterations in the intestinal microbiome appear to be key factors in the pathogenesis of necrotizing enterocolitis (NEC). The aim of this paper is to weigh the evidence for the use of probiotics to prevent NEC in premature infants.

METHODS

Animal studies, randomized controlled trials, observational cohort studies and meta-analyses involving administration of probiotic products for the prevention of NEC were reviewed. This review of the evidence summarizes the available preclinical and clinical data.

RESULTS

In animal models probiotic microbes alter the intestinal microbiome, decrease inflammation and intestinal permeability and decrease the incidence and severity of experimental NEC. In randomized, placebo-controlled trials and cohort studies of premature infants, probiotic microbes decrease the risk of NEC, death and sepsis.

CONCLUSION

Evidence is strong for the prevention of NEC with the use of combination probiotics in premature infants who receive breast milk. The potential risks and benefits of probiotic administration to premature infants should be carefully reviewed with parents.

TYPE OF STUDY

Therapeutic.

LEVEL OF EVIDENCE

I.

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.

Optimizing the Use of Medications and Other Therapies in Infant Gastroesophageal Reflux

Gastroesophageal reflux (GER) is the retrograde movement of gastric (and sometimes duodenal) contents into the esophagus. While the majority of GER is physiologic, for patients, it can be associated with symptoms. While some symptoms are merely bothersome (crying), others can be life threatening (cough, gagging, choking). The main driver of GER in infants is the frequent feedings that produce increased intra-abdominal pressure, which is known to trigger transient relaxations of the lower esophageal sphincter. The recent 2018 clinical practice guidelines reported by the North American and European Societies for Pediatric Gastroenterology, Hepatology and Nutrition (NASPGHAN/ESPGHAN) have recommended non-pharmacologic management initially with subsequent consideration of brief trials with acid suppressants. The main target for these acid suppressants is the gastric parietal cells. Our review of the literature has revealed a paucity of data regarding the use of histamine-2 receptor antagonists and proton pump inhibitors in infants. Despite the absence of well-controlled clinical studies, the prescription rate of these medications has increased internationally. Risks to patients of all ages have become increasingly recognized, with new associations being reported all too often. Here we report our review of all pharmacologic modalities as well as some non-surgical options.

Effect of fecal microbiota transplantation route of administration on gut colonization and host response in preterm pigs

This study examined gut colonization patterns and host responses to fecal microbiota transplantation (FMT) by different administration routes after preterm birth. In two separate experiments, cesarean-delivered, preterm pigs were administered combined oral + rectal, or exclusively rectal donor feces, and compared with saline controls. After 5 days, stomach and colon bacterial compositions were determined by 16S rRNA gene amplicon sequencing, and organic acid metabolites measured. Further, gut pathology, mucosa bacterial adherence, and goblet cell density were assessed. FMT increased the relative abundance of obligate anaerobes in the colon without affecting total bacterial load. Bacteroides colonized recipients despite low abundance in the donor feces, whereas highly abundant Prevotella and Ruminococcaceae did not. Further, FMT changed carbohydrate metabolism from lactate to propionate production thereby increasing colonic pH. Besides, FMT preserved goblet cell mucin stores and reduced necrotizing enterocolitis incidence. Only rectal FMT increased the stomach-to-colon pH gradient and resistance to mucosa bacterial adhesion. Conversely, oral + rectal FMT increased bacterial adhesion, internal organ colonization, and overall mortality. Our results uncovered distinctions in bacterial colonization patterns along the gastrointestinal tract, as well as host tolerability between oral and rectal FMT administration in preterm newborns. Besides, FMT showed the potential to prevent necrotizing enterocolitis.

Probiotics and necrotizing enterocolitis

In this review, we summarize existing knowledge regarding the effects of probiotics on necrotizing enterocolitis (NEC). We review the role of the microbiome in NEC and pre-clinical data on mechanisms of probiotic action. Next, we summarize existing randomized controlled trials and observational studies of probiotics to prevent NEC. We also summarize findings from several recent meta-analyses and report a new cumulative meta-analysis of probiotic trials. Finally, we review data from cohorts routinely using commercially available probiotics. Our goal is to inform clinicians about the risks and benefits of probiotics, which may be helpful for those considering use in preterm infants to prevent NEC, death, or sepsis.

Efficacy of and potential morbidities associated with the use of antacid medications in preterm neonates

OBJECTIVES

Antacid medications are frequently administered to preterm infants. These medications can change gastric pH levels and can affect regular gastrointestinal function and gut micro-bacterial flora. We hypothesized that preterm infants exposed to antacid medications are at a greater risk of necrotizing enterocolitis (NEC) and sepsis, and set out to determine any association, as well as to assess the clinical efficacy of these medications.

MATERIALS AND METHODS

Retrospective chart review of preterm infants ≤30 weeks' gestational age or birth weight ≤1250 g over a 2-year period at New York University Langone Medical Center. Subjects were divided into two groups: those who had been treated with antacid medications and those who had not. We then examined for any difference in NEC (≥Bell stage 2) or culture proven sepsis.

RESULTS

The study comprised 65 eligible neonates, 28 in antacid treatment group and 37 in control. The incidence of NEC (21.4% vs. 2.7%, P=0.04) was significantly higher in the antacid group, but these infants tended to be born more prematurely than control subjects. There was a trend toward more culture proven sepsis cases in the antacid group. We found no difference in signs generally associated with neonatal reflux (apnea, bradycardia, and desaturation events) in subjects treated with antacid medications after treatment began.

CONCLUSIONS

Treatment of preterm infants with antacid medications is potentially associated with a higher risk of NEC, and possibly sepsis, while appearing to provide little benefit.

Morbidity and Mortality in Preterm Infants following Antacid Use: A Retrospective Audit

Background and Objectives. Antacids are often prescribed to preterm infants due to misdiagnosis of gastro-oesophageal reflux. This suppresses gastric acidity, a major defence mechanism against infection. This study aims to determine if ranitidine and omeprazole use in very low birth weight (VLBW) neonates, <1500 grams, is associated with increased risk of late onset sepsis, necrotising enterocolitis (NEC), and mortality. Methods. Retrospective analysis was conducted on neonates, <1500 grams, born and admitted into the Neonatal Intensive Care Unit at The Canberra Hospital during the period from January 2008 to December 2012. Information regarding late onset sepsis, NEC, mortality, ranitidine/omeprazole use, and other neonatal/hospital factors was collected for each neonate. Results. 360 neonates were evaluated, 64 received ranitidine and/or omeprazole, and 296 had not. There were no statistically significant differences in incidence of late onset sepsis (OR = 0.52, CI = 0.24-1.1, and p = 0.117), NEC Stage 2 and above (OR = 0.4, CI = 0.05-3.2, and p = 0.7), or mortality (OR = 0.35, CI = 0.08-1.5, and p = 0.19) between the two groups. After adjusting significant differences in neonatal and hospital factors, risk of late onset sepsis was significantly lower in those that received ranitidine/omeprazole (OR = 0.28, CI = 0.13-0.65, and p = 0.003). Conclusions. Ranitidine and omeprazole use in VLBW preterm infants may not be associated with an increased risk of infection, NEC, and mortality.

Widespread use of gastric acid inhibitors in infants: Are they needed? Are they safe?

Gastroesophageal reflux is a common phenomenon in infants, but the differentiation between gastroesophageal reflux and gastroesophageal reflux disease can be difficult. Symptoms are non-specific and there is increasing evidence that the majority of symptoms may not be acid-related. Despite this, gastric acid inhibitors such as proton pump inhibitors are widely and increasingly used, often without objective evidence or investigations to guide treatment. Several studies have shown that these medications are ineffective at treating symptoms associated with reflux in the absence of endoscopically proven oesophagitis. With a lack of evidence for efficacy, attention is now being turned to the potential risks of gastric acid suppression. Previously assumed safety of these medications is being challenged with evidence of potential side effects including GI and respiratory infections, bacterial overgrowth, adverse bone health, food allergy and drug interactions.

Late Presentation of Fulminant Necrotizing Enterocolitis in a Child with Hyperinsulinism on Octreotide Therapy

Congenital hyperinsulinism (HI) is the most common cause of persistent hypoglycemia in infants and children. In cases of diazoxide-unresponsive HI, alternative medical and surgical approaches may be required to reduce the risk of hypoglycemia. Octreotide, a somatostatin analog, often has a role in the management of these children, but a dose-dependent reduction in splanchnic blood flow is a recognized complication. Necrotizing enterocolitis (NEC) has been reported within the first few weeks of initiating predominantly high doses of octreotide. We describe the case of an infant with Beckwith-Wiedemann syndrome and diazoxide-unresponsive HI, who had persistent hypoglycemia after two pancreatectomy surgeries. She developed NEC 2 months after beginning octreotide therapy at a relatively low dose of 8 µg/kg/day. This complication has occurred later, and at a lower dose, than has previously been described. We review the case and identify the known and suspected multifactorial risk factors for NEC that may contribute to the development of this complication in patients with HI.

The Evolution of Stomach Acidity and Its Relevance to the Human Microbiome

Gastric acidity is likely a key factor shaping the diversity and composition of microbial communities found in the vertebrate gut. We conducted a systematic review to test the hypothesis that a key role of the vertebrate stomach is to maintain the gut microbial community by filtering out novel microbial taxa before they pass into the intestines. We propose that species feeding either on carrion or on organisms that are close phylogenetic relatives should require the most restrictive filter (measured as high stomach acidity) as protection from foreign microbes. Conversely, species feeding on a lower trophic level or on food that is distantly related to them (e.g. herbivores) should require the least restrictive filter, as the risk of pathogen exposure is lower. Comparisons of stomach acidity across trophic groups in mammal and bird taxa show that scavengers and carnivores have significantly higher stomach acidities compared to herbivores or carnivores feeding on phylogenetically distant prey such as insects or fish. In addition, we find when stomach acidity varies within species either naturally (with age) or in treatments such as bariatric surgery, the effects on gut bacterial pathogens and communities are in line with our hypothesis that the stomach acts as an ecological filter. Together these results highlight the importance of including measurements of gastric pH when investigating gut microbial dynamics within and across species.

A randomised trial of re-feeding gastric residuals in preterm infants

OBJECTIVE

To determine whether re-feeding of gastric residual volumes reduces the time needed to achieve full enteral feeding in preterm infants.

DESIGN

Parallel-group randomised controlled trial with a 1:1 allocation ratio.

SETTING

Regional referral neonatal intensive care unit.

PATIENTS

72 infants of gestational age 23(0/7) to 28(6/7) weeks receiving minimal enteral nutrition (<24 mL/kg/day) during the first week after birth.

INTERVENTIONS

Infants were randomised to either be re-fed with gastric residual volumes (Re-feeding group) or receive fresh formula/human milk (Fresh-feeding group) whenever large gastric residual volumes were noted.

MAIN OUTCOME MEASURE

The primary efficacy end point was time to achieve full enteral feeding (≥120 mL/kg/day) after randomisation.

RESULTS

The mean time to full enteral feeding was 10.0 days in the Re-feeding group and 11.3 days in the Fresh-feeding group (mean difference favouring re-feeding: -1.3 days; 95% CI -2.9 to 0.3; p=0.11). The composite safety end point of spontaneous intestinal perforation, surgical necrotising enterocolitis, or death occurred in 6 of 36 infants (17%) in the Re-feeding group versus 10 of 36 infants (28%) in the Fresh-feeding group (p=0.26).

CONCLUSIONS

Re-feeding gastric residual volumes in extremely preterm infants does not reduce time to achieve full enteral feeding. This trial suggests that re-feeding might be as safe as fresh feeding, but further research is needed, due to lack of sufficient statistical power in this study for safety analysis.

TRIAL REGISTRATION NUMBER

NCT01420263NCT01420263.

Novel approaches to improve the intrinsic microbiological safety of powdered infant milk formula

Human milk is recognised as the best form of nutrition for infants. However; in instances where breast-feeding is not possible, unsuitable or inadequate, infant milk formulae are used as breast milk substitutes. These formulae are designed to provide infants with optimum nutrition for normal growth and development and are available in either powdered or liquid forms. Powdered infant formula is widely used for convenience and economic reasons. However; current manufacturing processes are not capable of producing a sterile powdered infant formula. Due to their immature immune systems and permeable gastro-intestinal tracts, infants can be more susceptible to infection via foodborne pathogenic bacteria than other age-groups. Consumption of powdered infant formula contaminated by pathogenic microbes can be a cause of serious illness. In this review paper, we discuss the current manufacturing practices present in the infant formula industry, the pathogens of greatest concern, Cronobacter and Salmonella and methods of improving the intrinsic safety of powdered infant formula via the addition of antimicrobials such as: bioactive peptides; organic acids; probiotics and prebiotics.

Developmental aspects of maternal-fetal, and infant gut microbiota and implications for long-term health

Background

Early life interactions between the human host and microbes set the stage for future health and disease.

Findings

In this review, some of the relationship of the human microbiome effects will be discussed as they relate to preterm delivery, early life diseases seen in prematurely delivered infants, and other childhood and adult maladies which include autoimmunity, allergic diseases, obesity or a healthy phenotype.

Conclusion

Although the data in these areas is just beginning to emerge, this review will provide a brief summary of some of the key research being done and will also speculate on emerging areas where major questions are being raised.

Predicting disease severity of necrotizing enterocolitis: how to identify infants for future novel therapies

Necrotizing enterocolitis (NEC) remains a very devastating problem within the very low birth weight neonatal population. Several experimental therapies are being tested in animal models and soon may be ready for human trials. Despite this progress, we currently have no way to identify infants who would be optimal targets for therapy. Specifically, we are unable to predict which infants will progress to the more severe Bell's stage of disease that may necessitate surgery. Ideally, an algorithm could be constructed that would encompass multiple neonatal and maternal risk factors as well as potential biologic markers of disease so that these infants could be identified in a more timely fashion. This review summarizes the known risk factors and biomarkers of disease in hopes of stimulating clinical research to identify such an “early warning” NEC algorithm.

Neonatal necrotizing enterocolitis: Clinical challenges, pathophysiology and management

NEC remains a major concern for neonatologists, surgeons, and gastroenterologists due to its high morbidity and mortality. These infants often have poor developmental outcome, and contribute to significant economic burden resulting in marked stress in these families. By developing and adhering to strict feeding protocols, encouraging human milk feeding preferably from the infant's mother, use of probiotics, judicious antibiotic use, instituting blood transfusion protocols, the occurrence of NEC may possibly be reduced. However, because of its multifactorial etiology, it cannot be completely eradicated in the NICUs, particularly in the extremely premature infants. Ongoing surveillance of NEC and quality improvement projects may be beneficial.

Pharmacological therapy of gastroesophageal reflux in preterm infants

Although gastroesophageal reflux (GER) is a very common phenomenon among preterm infants, its therapeutic management is still an issue of debate among neonatologists. A step-wise approach should be advisable, firstly promoting nonpharmacological interventions and limiting drugs to selected infants unresponsive to the conservative measures or who are suffering from severe GER with clinical complications. Despite of this, a concerning pharmacological overtreatment has been increasingly reported. Most of the antireflux drugs, however, have not been specifically assessed in preterm infants; moreover, serious adverse effects have been noticed in association to their administration. This review mainly aims to draw the state of the art regarding the pharmacological management of GER in preterm infants, analyzing the best piecies of evidence currently available on the most prescribed anti-reflux drugs. Although further trials are required, sodium alginate-based formulations might be considered promising; however, data regarding their safety are still limited. Few piecies of evidence on the efficacy of histamine-2 receptor blockers and proton pump inhibitors in preterm infants with GER are currently available. Nevertheless, a significantly increased risk of necrotizing enterocolitis and infections has been largely reported in association with their use, thereby leading to an unfavorable risk-benefit ratio. The efficacy of metoclopramide in GER's improvement still needs to be clarified. Other prokinetic agents, such as domperidone and erythromycin, have been reported to be ineffective, whereas cisapride has been withdrawn due to its remarkable cardiac adverse effects.

Histamine-2 receptor blockers alter the fecal microbiota in premature infants

OBJECTIVES

Bacterial colonization is considered a major risk factor for necrotizing enterocolitis (NEC). The objective of the present study was to test the hypothesis that histamine-2 receptor (H2-) blockers alter colonic bacterial colonization by analyzing and comparing the fecal microbiota in premature infants with and without H2-blocker therapy using sensitive molecular biological techniques.

METHODS

Seventy-six premature infants ≤1500 g or <34 weeks gestation were enrolled in this case-controlled, cross-sectional study. Stool samples were collected from 25 infants receiving H2-blockers and 51 babies who had never received them. Following DNA extraction and PCR amplification of 16S rRNA, 454 pyrosequencing was undertaken and the resulting sequences were subjected to comparison with published sequence libraries.

RESULTS

Proteobacteria and Firmicutes were the major phyla contributing to fecal microbial communities. Microbial diversity was lower, relative abundance of Proteobacteria (primarily of the family Enterobacteriaceae) was increased, whereas that of Firmicutes was decreased in the stools of infants receiving H2-blockers compared with those who had never received them.

CONCLUSIONS

Although not designed to look specifically at the effect of H2-blockers on the incidence of NEC, our study suggests that their use lowers fecal microbial diversity and shifts the microfloral pattern toward Proteobacteria. These alterations in fecal microbiota may predispose the vulnerable immature gut to necrotizing enterocolitis and suggest prudence in the use of H2-blockers in the premature infant.

The altered gut microbiome and necrotizing enterocolitis

Current evidence highlights the importance of developing a healthy intestinal microbiota in the neonate. Many aspects that promote health or disease are related to the homeostasis of these intestinal microbiota. Their delicate equilibrium could be strongly influenced by the intervention that physicians perform as part of the medical care of the neonate, especially preterm infants. As awareness of the importance of the development and maintenance of these intestinal flora increase and newer molecular techniques are developed, it will be possible to provide better care of infants with interventions that will have long-lasting effects.

Are there risks associated with empiric acid suppression treatment of infants and children suspected of having gastroesophageal reflux disease?

BACKGROUND

It has become common practice to empirically treat infants and children who have suspected gastroesophageal reflux disease by using acid-suppressive medications. However, evidence to support the effectiveness of these medications in the pediatric population is limited. With multiple studies in adult patients indicating increased risk of infection, we reviewed the literature to determine the association between acid-suppressive medications and serious adverse effects in infants and children.

METHODS

We conducted a PubMed search on the adverse effects of H2 antagonists and proton pump inhibitors in pediatric patients. The studies selected were original research and systematic reviews with control groups and study objectives evaluating the relationship between acid-suppressive medications and serious adverse effects (namely, infections).

RESULTS

Fourteen studies met our inclusion criteria. The majority of studies found a significant association between acid-suppressive medications and the risk of necrotizing enterocolitis, sepsis/bacteremia, pneumonia, and gastrointestinal infections in infants and children.

CONCLUSIONS

Given the questionable efficacy of H2 antagonists and proton pump inhibitors and the growing evidence of increased risk of serious infections, acid-suppressive medications should be used cautiously in infants and children suspected of having gastroesophageal reflux disease.

Necrotizing enterocolitis in very low birth weight infants: a systemic review

Necrotizing enterocolitis (NEC) is the most common serious gastrointestinal disorder affecting very preterm or very low birth weight infants. The risk is inversely proportional to gestational age and weight at birth. Fetal growth restriction and compromise may be additional specific risk factors. Despite extensive research and animal studies etiopathogenesis, preventive strategies and management options remain controversial. The present paper reviews the literature for recent advances and newer insights for changing epidemiological trends, pathogenesis, role of inflammatory cytokines, and various preventive and management strategies.

Intestinal microbiota and blue baby syndrome: probiotic therapy for term neonates with cyanotic congenital heart disease

Necrotizing enterocolitis (NEC) is the most common intestinal emergency among premature infants. Risk factors in premature infants include immature intestinal immunity and an intestinal microbiota dominated by hospital-acquired bacteria. Some probiotics have been shown to decrease the incidence of NEC in premature infants. Among term infants, NEC is rare. However, among term infants with cyanotic congenital heart disease (CCHD), the incidence of NEC is similar to that of premature infants but with even greater mortality rates. Mechanisms by which NEC occurs in term infants with CCHD are unknown. Of central interest is the potential role of changes in the intestinal microbiota and whether these can be modified with probiotic bacteria; accordingly, we review the literature, propose hypotheses and present the rationale for future studies involving preliminary probiotic clinical trials.

Prevention of necrotising enterocolitis: Year 2004 and beyond

The incidence of necrotising enterocolitis (NEC) has not changed significantly despite the dramatic advances in perinatal-neonatal care. The absolute number of survivors of NEC is expected to rise, as prevention of prematurity, the single most important risk factor for the illness, continues to be difficult. Prevention of NEC has thus become an area of research priority. Given the role of inflammatory mediators in its pathogenesis newer immune modulators are being studied as potential agents for prevention/treatment of NEC. Caution, however, is warranted because the failure of sepsis trials in adults has clearly indicated that the concept of down-regulating the inflammatory response is deceptively simple. Clinical trials of any such promising preventative agent(s) need to be designed carefully and must include long-term neurodevelopmental outcomes as almost an entire population of high-risk preterm neonates will be exposed to their adverse effects. As new frontiers continue to be explored, the proven benefits of simple and safe interventions like antenatal glucocorticoid therapy and the preferential use of breast milk for feeding high-risk neonates must not be forgotten. Given that a single effective agent is unlikely in the near future, utilizing a package of "potentially better practices" seems to be the most appropriate strategy to prevent and minimize NEC.

Probiotic fortified diet reduces bacterial colonization and translocation in a long-term neonatal rabbit model

BACKGROUND

Probiotic fortified diet reduces bacterial colonization and translocation in a short-term neonatal rabbit model when continuously challenged with pathogen. The purpose of this study was to determine if live probiotic diet could remain effective at decreasing colonization/translocation of pathogens in a long-term neonatal rabbit model without ill effects of the probiotic outside the gastrointestinal (GI) tract.

METHODS

Rabbit pups were born via cesarean delivery 1 day preterm and assigned to 2 diets: a newly formulated diet (controls) vs the same diet fortified with the live probiotic Lactoccocus lactis. Enterobacter cloacae was added to both preparations before each feed. Pups were gavage fed twice daily, and weights were recorded. Rabbits were sacrificed on day 7, and organs were harvested and cultured for target organism growth.

RESULTS

The probiotic fortified diet resulted in a significant decrease in Enterobacter translocation to the liver and decreased colonization in the stomach and lungs. There was no evidence of Lactococccus translocation or colonization outside of the GI tract.

CONCLUSION

This probiotic fortified diet was effective at decreasing pathogenic bacteria colonization and translocation in a long-term neonatal model. The addition of L lactis to the diet resulted in appropriate growth without any colonization or translocation of the probiotic outside of the GI tract.

Probiotic acidified formula in an animal model reduces pulmonary and gastric bacterial load

BACKGROUND/PURPOSE

We previously reported that a diet acidified with citric acid effectively reinforces gastric acid protection against bacterial colonization and translocation. In this study, our objective was to examine a biologically acidified formula hypothesized to be more physiologic than formula acidified with free acid. This study was Institutional Animal Care and Use Committee (IACUC) approved and designed to determine whether this diet is better tolerated and equally effective to acidification with citric acid against gut colonization and subsequent bacterial translocation in a premature infant rabbit model.

METHODS

A total of 89 rabbit pups born via cesarean delivery 1 day preterm were randomly assigned to 3 feeding groups: Pelargon Nestle at pH 4.55; NAN Nestle, a control diet at pH 7.0 with similar composition; and NAN Nestle acidified in the laboratory with citric acid at pH 4.55. Pups were gavage fed every 12 hours with Enterobacter cloacae challenges of 10 colony-forming units per milliliter of diet per feed and killed on day 3 of life. Lungs, liver, spleen, mesenteric lymph nodes, stomach, and cecum were cultured and quantitatively analyzed for target organism growth and statistically analyzed using chi(2) and Kruskal-Wallis tests.

RESULTS

Pelargon, compared to acidified NAN and NAN, significantly reduced the incidence of gastric colonization (15/33 [45%], 21/27 [78%], and 25/29 [86%], respectively; P < .01) and pulmonary colonization (10/33 [30%], 19/27 [70%], 21/29 [72%]; P < .01). Comparing the bacterial logs of colonized groups, the same benefit is observed in the lungs (0.77 +/- 1.22, 1.89 +/- 1.41, 2.12 +/- 1.47; P < .01). Gut colonization and bacterial translocation were equivalent between treatment groups (mesenteric lymph nodes: 10/33 [30%], 11/27 [40%], 8/29 [27%]; spleen: 10/33 [30%], 7/27 [26%], 8/29 [27%]; liver: 10/33 [30%], 6/27 [22%], 9/29 [31%]; cecum: 33/33 [100%], 27/27 [100%], 29/29 [100%]).

CONCLUSION

Biologically acidified formula demonstrated superior protection against pulmonary and gastric colonization compared to normal pH and diets acidified with free acid. Its effects may potentially reduce clinical pulmonary infection.

Necrotizing enterocolitis: A multifactorial disease with no cure

Necrotizing enterocolitis is an inflammatory bowel disease of neonates with significant morbidity and mortality in preterm infants. Due to the multifactorial nature of the disease and limitations in disease models, early diagnosis remains challenging and the pathogenesis elusive. Although preterm birth, hypoxic-ischemic events, formula feeding, and abnormal bacteria colonization are established risk factors, the role of genetics and vasoactive/inflammatory mediators is unclear. Consequently, treatments do not target the specific underlying disease processes and are symptomatic and surgically invasive. Breast-feeding is the most effective preventative measure. Recent advances in the prevention of necrotizing enterocolitis have focused on bioactive nutrients and trophic factors in human milk. Development of new disease models including the aspect of prematurity that consistently predisposes neonates to the disease with multiple risk factors will improve our understanding of the pathogenesis and lead to discovery of innovative therapeutics.

Formula fortified with live probiotic culture reduces pulmonary and gastrointestinal bacterial colonization and translocation in a newborn animal model

BACKGROUND/PURPOSE

Acidified diets are protective against intestinal bacterial colonization and translocation. Probiotic diets are designed to modulate the intestinal flora to enhance mucosal immunity. This study was designed to determine if formula acidified with live probiotic decreases bacterial gut colonization and translocation, and is equally tolerated as other acidified diets.

METHODS

One hundred twenty-eight rabbit pups delivered via cesarean section [cesarean delivery, cesarean birth, abdominal delivery] were randomly assigned to 4 feeding groups: NAN Nestle (control, pH 7.0), NAN acidified with citric acid (pH 4.55), biologically acidified Pelargon (pH 4.55), and NAN with live Lactococcus lactis culture (pH 4.2). Pups were gavage fed every 12 hours with Enterobacter cloacae challenges of 10 colony-forming units/mL per feed and killed on day of life 3. Lungs, liver, spleen, mesenteric lymph nodes (MLNs), stomach, and cecum were cultured and quantitatively analyzed for target organism growth. Results were analyzed using chi(2) tests.

RESULTS

NAN with live probiotic culture, when compared with Pelargon, acidified NAN, and NAN, significantly reduced the incidence of Enterobacter pulmonary colonization (P < .01), bacterial translocation (liver, P < .025; spleen and MLN, P < .05), and gastric and intestinal colonization (P < .001 for both).

CONCLUSION

Probiotic-fortified formula provides superior protection against pulmonary and gastrointestinal bacterial colonization and translocation compared with neutral and acidified formulas, and is equally tolerated.

National Institues of Health recommends the routine use of H2 blockers in preterm infants be carefully evaluated

ARETROSPECTIVE ANALYSIS OF data from 11,000 preterm infants in neonatal intensive care units (NICUs) in the U.S. found that infants receiving H2 blockers such as Zantac, Tagamet, Pepcid, and Axid were more likely to develop necrotizing enterocolitis (NEC).1 The study was funded by the National Institutes of Health (NIH). As a result of the findings of this study, Elias A. Zerhouni, MD, Director of the National Institutes of Health, issued a press release in February, 2006, stating, “This study strongly suggests that the current practice of prescribing H2 blockers to prevent or treat acid reflux in premature infants needs to be carefully reevaluated by all concerned in light of these new findings.”2

Association of H2-blocker therapy and higher incidence of necrotizing enterocolitis in very low birth weight infants

OBJECTIVE

We sought to determine if an association exists between the use of histamine-2 receptor (H2) blockers and the incidence of necrotizing enterocolitis (NEC) in infants of 401 to 1500 g in birth weight.

STUDY DESIGN

Data from the National Institute of Child Health and Human Development Neonatal Research Network very low birth weight (401-1500 g) registry from September 1998 to December 2001 were analyzed. The relation between the diagnosis of NEC (Bell stage II or greater) and antecedent H2-blocker treatment was determined by using case-control methodology. Conditional logistic regression was implemented, controlling for gender, site of birth (outborn versus inborn), Apgar score of < 7 at 5 minutes, and postnatal steroids.

RESULTS

Of 11072 infants who survived for at least 12 hours, 787 (7.1%) developed NEC (11.5% of infants 401-750 g, 9.1% of infants 751-1000 g, 6.0% of infants 1001-1250 g, and 3.9% of infants 1251-1500 g). Antecedent H2-blocker use was associated with an increased incidence of NEC (P < .0001).

CONCLUSIONS

H2-blocker therapy was associated with higher rates of NEC, which is in agreement with a previous randomized trial of acidification of infant feeds that resulted in a decreased incidence of NEC. In combination, these data support the hypothesis that gastric pH level may be a factor in the pathogenesis of NEC.

Feeding intolerance in very-low-birthweight infants: what is it and what can we do about it?

The increased survival of very-low-birth-weight infants has resulted in the need to better understand the immaturities that challenge optimal nutrition for these infants and how to surmount them. This is critical if we are to prevent short and long term morbidity associated with poor nutrition. Here we describe several of these immaturities including those related to digestion and absorption, suck-swallow incoordination, delayed gastric emptying, and intestinal motility and how they lead to the common problem of feeding intolerance. Scientifically based strategies for introducing, stopping and continuing enteral feedings in association with parenteral nutrition are presented.

Clinical microbiology of bacterial and fungal sepsis in very-low-birth-weight infants

Twenty percent of very-low-birth-weight (<1500 g) preterm infants experience a serious systemic infection, and despite advances in neonatal intensive care and antimicrobials, mortality is as much as threefold higher for these infants who develop sepsis than their counterparts without sepsis during their hospitalization. Outcomes may be improved by preventative strategies, earlier and accurate diagnosis, and adjunct therapies to combat infection and protect the vulnerable preterm infant during an infection. Earlier diagnosis on the basis of factors such as abnormal heart rate characteristics may offer the ability to initiate treatment prior to the onset of clinical symptoms. Molecular and adjunctive diagnostics may also aid in diagnosing invasive infection when clinical symptoms indicate infection but no organisms are isolated in culture. Due to the high morbidity and mortality, preventative and adjunctive therapies are needed. Prophylaxis has been effective in preventing early-onset group B streptococcal sepsis and late-onset Candida sepsis. Future research in prophylaxis using active and passive immunization strategies offers prevention without the risk of resistance to antimicrobials. Identification of the differences in neonatal intensive care units with low and high infection rates and implementation of infection control measures remain paramount in each neonatal intensive care unit caring for preterm infants.

Treatment and prevention of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the most common serious, acquired gastrointestinal disorder in the newborn infant. Although many variables are associated with development of NEC, only prematurity has been consistently identified in case-controlled studies. Traditionally, the diving seal reflex has been invoked as the mechanism responsible for ischaemic injury and necrosis. Intestinal ischaemia is likely to be the final common pathway in NEC; however, it is due to the release of vasoconstricting substances, such as platelet activating factor, rather than perinatal asphyxia. Bacteria and/or bacterial toxins are likely to have a key role in the pathogenesis of NEC by fostering production of inflammatory mediators. The role of feeding practices in the pathogenesis of NEC remains controversial. Treatment of infants with NEC generally includes a regimen of bowel rest, gastric decompression, systemic antibiotics and parenteral nutrition. Infants with perforation are generally operated upon; however, there has been recent interest in primary peritoneal drainage as an alternative. Prevention of NEC still remains elusive. Avoidance of preterm birth, use of antenatal steroids and breast-milk feeding are practices that offer the greatest potential benefits. Use of any other strategy should await further trials.

Neonatal necrotizing enterocolitis: an overview

PURPOSE OF REVIEW

Necrotizing enterocolitis represents a disease entity that remains quite challenging for neonatologists all around the world, in that its aetiology has yet to be revealed, but it is the cause of death for many premature infants each year, affecting up to 28% of very low birthweight infants. This is an attempt to improve the management of affected babies and stimulate more research concerning new diagnostic tools.

RECENT FINDINGS

Current trends in the field of (early) diagnosis, such as: (1) imaging techniques, e.g. contrast radiography, portal vein ultrasonography, magnetic resonance, radionuclide scanning; (2) gastrointestinal tonometry; (3) the detection of biochemical markers, cytokines, growth factors; and (4) the determination of the mean peak hydrogen: carbon dioxide ratio excreted in breath, are only some of those mentioned. Various novel preventive techniques are also presented, among which platelet-activating factor acetyl hydrolase activity enhancement, platelet-activating factor receptor antagonists and probiotics, such as Bifidobacterium infantis and Lactobacillus acidophilus, seem quite promising. Regarding treatment, the use of oxygenated perfluorocarbon has added to the limited alternatives available. These data along with other recent discoveries concerning the risk factors and pathogenesis of this disease create a full picture of the current opinion on this topic.

SUMMARY

Keeping in mind that the key to confronting such a devastating disorder as necrotizing enterocolitis is early diagnosis and prevention, both clinically applicable and experimental advances are presented with the hope of improving the survival rates of patients affected.

Acidification of formula with citric acid is equally effective and better tolerated than acidification with hydrochloric acid

OBJECTIVE

To determine whether acidification of formula with citric acid is equally protective against bacterial translocation and gut colonization but better tolerated than acidification with hydrochloric acid in neonatal rabbits.

DESIGN

Paired animal model with control.

SETTING

Animal laboratory.

SUBJECTS

Premature neonatal New Zealand rabbit pups.

INTERVENTIONS

A standard neonatal rabbit model in two versions, a bacterial challenge and a no bacterial challenge model, was used to assess bacterial translocation and gut colonization. Two hundred forty-six rabbit pups were delivered by cesarean section 1 day premature and randomly placed into two groups sorted by type of formula acidification (hydrochloric acid or citric acid). Pups were gavage fed pH 3 kitten formula every 12 hrs. Ranitidine hydrochloride at 20 mg x kg(-1) x day(-1) was added to all formula. Bacterial challenge animals were given 1 x 10(6) colony-forming units/mL of Enterobacter cloacae with the third feeding. Animals in the no bacterial challenge group received no bacterial challenge. Animals were killed on day of life 3, and the liver, spleen, mesenteric lymph nodes, and cecum were sequentially harvested and cultured. Organs were qualitatively judged for growth, whereas cecal cultures were quantified as colony-forming units/gram. Stomach biopsies were performed to look for mucosal damage. Long-term tolerance was assessed in 48 pups fed formula acidified to pH 3 with either hydrochloric acid or citric acid and 20 animals fed pH 7 formula without ranitidine. Weight gain and mortality rate were followed for 14 days.

MEASUREMENTS AND MAIN RESULTS

Gut colonization and bacterial translocation to liver, spleen, and mesenteric lymph nodes were equivalent between citric acid and hydrochloric acid in both bacterial challenge and no bacterial challenge models. Long term, citric acid animals exceeded hydrochloric acid animals in daily weight gain and survival (p <.05 for both) and equaled pH 7 animals in these measurements.

CONCLUSION

Acidification of formula with citric acid is equally protective against bacteria but better tolerated than acidification with hydrochloric acid.