Gut microbiota in preterm infants: assessment and relevance to health and disease

Effect of an Exclusive Human Milk Diet on the Gut Microbiome in Preterm Infants: A Randomized Clinical Trial

IMPORTANCE

The effect of using an exclusive human milk diet compared with one that uses bovine products in preterm infants is uncertain, but some studies demonstrate lower rates of key neonatal morbidities. A potential mediating pathway is the gut microbiome.

OBJECTIVE

To determine the effect of an exclusive human milk diet on gut bacterial richness, diversity, and proportions of specific taxa in preterm infants from enrollment to 34 weeks' postmenstrual age.

DESIGN, SETTING, AND PARTICIPANTS

In this randomized clinical trial conducted at 4 neonatal intensive care units in the United Kingdom from 2017 to 2020, microbiome analyses were blind to group. Infants less than 30 weeks' gestation who had only received own mother's milk were recruited before 72 hours of age. Statistical analysis was performed from July 2019 to September 2021.

INTERVENTIONS

Exclusive human milk diet using pasteurized human milk for any shortfall in mother's own milk supply and human milk-derived fortifiers (intervention) compared with bovine formula and bovine-derived fortifier (control) until 34 weeks' postmenstrual age. Fortifier commenced less than 48 hours of tolerating 150 mL/kg per day.

MAIN OUTCOMES AND MEASURES

Gut microbiome profile including alpha and beta diversity, and presence of specific bacterial taxa.

RESULTS

Of 126 preterm infants enrolled in the study, 63 were randomized to control (median [IQR] gestation: 27.0 weeks [26.0-28.1 weeks]; median [IQR] birthweight: 910 g [704-1054 g]; 32 [51%] male) and 63 were randomized to intervention (median [IQR] gestation: 27.1 weeks [25.7-28.1 weeks]; median [IQR] birthweight: 930 g [733-1095 g]; 38 [60%] male); 472 stool samples from 116 infants were analyzed. There were no differences in bacterial richness or Shannon diversity over time, or at 34 weeks between trial groups. The exclusive human milk diet group had reduced relative abundance of Lactobacillus after adjustment for confounders (coefficient estimate, 0.056; P = .03), but not after false discovery rate adjustment. There were no differences in time to full feeds, necrotizing enterocolitis, or other key neonatal morbidities.

CONCLUSIONS AND RELEVANCE

In this randomized clinical trial in preterm infants using human milk-derived formula and/or fortifier to enable an exclusive human milk diet, there were no effects on overall measures of gut bacterial diversity but there were effects on specific bacterial taxa previously associated with human milk receipt. These findings suggest that the clinical impact of human milk-derived products is not modulated via microbiomic mechanisms.

TRIAL REGISTRATION

ISRCTN trial registry identifier: ISRCTN16799022.

Gut Dysbiosis in Children with Cystic Fibrosis: Development, Features and the Role of Gut-Lung Axis on Disease Progression

Cystic fibrosis (CF) is the most common autosomal recessive disease among Caucasians. Over the last 20 years, culture-independent analysis, including next-generation sequencing, has paired with culture-based microbiology, offering deeper insight into CF lung and gut microbiota. The aim of this review is to analyse the features of gut microbiota in patients with CF and its possible role in the progression of the disease, establishing the basis for a potential role in microbe-based therapies. The literature analysis showed that the gut environment in CF patients has unique features due to the characteristics of the disease, such as decreased bicarbonate secretion, increased luminal viscosity, and an acidic small intestinal environment, which, due to the treatment, includes regular antibiotic use or a high-energy and fat-dense diet. As a result, the gut microbial composition appears altered, with reduced richness and diversity. Moreover, the population of pro-inflammatory bacteria is higher, while immunomodulatory genera, such as Bacteroides and Bifidobacterium, are scarcer. The imbalanced gut microbial population has a potential role in the development of systemic inflammation and may influence clinical outcomes, such as respiratory exacerbations, spirometry results, and overall growth. Although a better understanding of the pathophysiology behind the gut-lung axis is needed, these findings support the rationale for considering gut microbiota manipulation as a possible intervention to regulate the severity and progression of the disease.

Exploring the long-term colonisation and persistence of probiotic-prophylaxis species on the gut microbiome of preterm infants: a pilot study

Preterm infants suffer from a higher incidence of acute diseases such as necrotising enterocolitis and sepsis. This risk can be mitigated through probiotic prophylaxis during admission. This reduction in risk is likely the result of acute modulation of the gut microbiome induced by probiotic species, which has been observed to occur up until discharge. We aimed to determine if this modulation, and the associated probiotic species, persisted beyond discharge. We conducted both a cross-sectional analysis (n = 18), at ~ 18 months of age, and a longitudinal analysis (n = 6), from admission to 18 months of the gut microbiome of preterm infants using both shotgun metagenomics and 16S rRNA profiling respectively. The 16S amplicon sequencing revealed that the microbial composition of the probiotic-supplemented infants changed dramatically over time, stabilising at discharge. However, species from the probiotic Infloran^®, as well as positive modulatory effects previously associated with supplementation, do not appear to persist beyond discharge and once prophylaxis has stopped.    Conclusions: Although differences exist between supplemented and non-supplemented groups, the implications of these differences remain unclear. Additionally, despite a lack of long-term colonisation, the presence of probiotics during early neonatal life may still have modulatory effects on the microbiome assembly and immune system training. What is Known: • Evidence suggests modulation of the microbiome occurs during probiotic prophylaxis, which may support key taxa that exert positive immunological benefits. • Some evidence suggests that this modulation can persist post-prophylaxis. What is New: • We present support for long-term modulation in association with probiotic prophylaxis in a cohort of infants from North Queensland Australia. • We also observed limited persistence of the probiotic species post-discharge.

To Probiotic or Not to Probiotic: A Metagenomic Comparison of the Discharge Gut Microbiome of Infants Supplemented With Probiotics in NICU and Those Who Are Not

BACKGROUND

Preterm birth is associated with the development of both acute and chronic disease, and the disruption of normal gut microbiome development. Recent studies have sought to both characterize and understand the links between disease and the microbiome. Probiotic treatment may correct for these microbial imbalances and, in turn, mitigate disease. However, the criteria for probiotic supplementation in NICU's in North Queensland, Australia limits its usage to the most premature (<32 weeks gestation) and small for gestational age infants (<1,500 g). Here we use a combination of amplicon and shotgun metagenomic sequencing to compare the gut microbiome of infants who fulfill the criteria for probiotic-treatment and those who do not. The aims of this study were to determine if probiotic-supplemented preterm infants have significantly different taxonomic and functional profiles when compared to non-supplemented preterm infants at discharge.

METHODS

Preterm infants were recruited in North Queensland, Australia, with fecal samples collected just prior to discharge (36 ± 0.5 weeks gestation), to capture potential changes that could be probiotic induced. All samples underwent 16S rRNA gene amplicon sequencing, with a subset also used for shotgun metagenomics. Mixed effects models were used to assess the effect of probiotics on alpha diversity, beta diversity and taxonomic abundance, whilst accounting for other known covariates.

RESULTS

Mixed effects modeling demonstrated that probiotic treatment had a significant effect on overall community composition (beta diversity), characterized by greater alpha diversity and differing abundances of several taxa, including Bifidobacterium and Lactobacillus, in supplemented infants.

CONCLUSION

Late preterm-infants who go without probiotic-supplementation may be missing out on stabilizing-effects provided through increased alpha diversity and the presence of commensal microbes, via the use of probiotic-treatment. These findings suggest that late-preterm infants may benefit from probiotic supplementation. More research is needed to both understand the consequences of the differences observed and the long-term effects of this probiotic-treatment.

Optimisation and Application of a Novel Method to Identify Bacteriophages in Maternal Milk and Infant Stool Identifies Host-Phage Communities Within Preterm Infant Gut

Human milk oligosaccharides, proteins, such as lactoferrin, and bacteria represent just some of the bioactive components of mother's breast milk (BM). Bacteriophages (viruses that infect bacteria) are an often-overlooked component of BM that can cause major changes in microbial composition and metabolism. BM bacteriophage composition has been explored in term and healthy infants, suggesting vertical transmission of bacteriophages occurs between mothers and their infants. Several important differences between term and very preterm infants (<30 weeks gestational age) may limit this phenomenon in the latter. To better understand the link between BM bacteriophages and gut microbiomes of very preterm infants in health and disease, standardised protocols are required for isolation and characterisation from BM. In this study, we use isolated nucleic acid content, bacteriophage richness and Shannon diversity to validate several parameters applicable during bacteriophage isolation from precious BM samples. Parameters validated include sample volume required; centrifugal sedimentation of microbes; hydrolysis of milk samples with digestive enzymes; induction of temperate bacteriophages and concentration/purification of isolated bacteriophage particles in donor milk (DM). Our optimised method enables characterisation of bacteriophages from as little as 0.1 mL BM. We identify viral families that were exclusively identified with the inclusion of induction of temperate bacteriophages (Inoviridae) and hydrolysis of milk lipid processes (Iridoviridae and Baculoviridae). Once applied to a small clinical cohort we demonstrate the vertical transmission of bacteriophages from mothers BM to the gut of very preterm infants at the species level. This optimised method will enable future research characterising the bacteriophage composition of BM in very preterm infants to determine their clinical relevance in the development of a healthy preterm infant gut microbiome.

Feeding Strategies in Preterm Very Low Birth-Weight Infants: State-of-the-Science Review

BACKGROUND

Providing enteral feeds to preterm very low birth-weight (VLBW) infants is critical to optimize nutrition, enhance growth, and reduce complications. Protocols guiding feeding practices can improve outcomes, but significant variation exists between institutions, which may limit their utility. To be most effective, protocols should be based on the best available evidence.

PURPOSE

To examine the state of the science on several key components of feeding protocols for VLBW infants.

SEARCH STRATEGY

The authors searched PubMed, CINAHL, and EMBASE databases for terms related to feeding VLBW infants less than 32 weeks' gestational age, including initiation of feedings, rate of feeding advancement, timing of human milk (HM) fortification, and feeding during blood transfusions, when diagnosed with a patent ductus arteriosus (PDA) and during medical treatment of PDA closure.

RESULTS

Initiation of feeds within the first 3 days of life and advancement by 30 mL/kg/d may decrease time to attain full feeds without increasing complications. Insufficient evidence guides optimal timing of HM fortification, as well as feeding infants undergoing blood transfusions, infants diagnosed with a PDA, and infants receiving medical treatment of PDA closure.

IMPLICATIONS FOR PRACTICE

Integration of existing research regarding feeding initiation and advancement into feeding protocols may improve outcomes. Infants at highest risk of feeding-related complications may benefit from a personalized feeding approach.

IMPLICATIONS FOR RESEARCH

Additional research is needed to provide evidence concerning the optimal timing of HM fortification and feeding strategies for infants undergoing blood transfusions and those diagnosed with a PDA or receiving medical treatment of PDA closure to incorporate into evidence-based feeding protocols.

How Gut Microbiota Supports Immunity, Growth and Development of Preterm Infants: A Narrative Review

ABSTRACTBackground: Gut microbiota, a complex ecosystem consisting of abundant microorganisms, plays a role in preterm infants’ immunity, growth, and development. Dysbiosis or disruption of the gut microbiota can precipitate various diseases, such as allergy or autoimmune disorders in premature infants. Purpose: This study aimed to review gut microbiota in preterm infants and its role in supporting the infants’ immunity, growth, and development. Discussion: Bifidobactericeae is the predominant microbiota in GI tract of preterm infants. However, various factors can influence this gut microbiota e.g., genetics, lifestyle of the mothers (smoking, diet, use of antibiotic, obesity), birth mode, type of feeding, and environmental factors. Gut dysbiosis can result in impaired immune system which predisposes the preterm infants to infections, even fatal adverse event. Furthermore, the growth and development might be affected as well as lead to various neurodevelopmental and psychiatric disorders. Human milk is a prebiotic source which can stimulate the growth of Baifidobactericeae and Bacteroidetes. If the human milk is inadequate or unavailable, the recommended interventions for gut dysbiosis in premature infants are probiotics, prebiotics, or both supplementations (synbiotics). The administration of prebiotics and probiotics associates with lower morbidity and death rates in preterm infants, as well as shorter duration of hospital stay and duration to achieve full enteral feeding. Conclusions: Immunity as well as growth and development of preterm infants are affected greatly by gut microbiota The less diverse microbiota in preterm infants’ gut predispose them to various health problems. Hence, this problem should be managed properly, one of which is prebiotic and probiotic supplementation Keywords: Gastrointestinal Microbiome, Premature, Immunity, Growth, Development

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.

Use of omic technologies in early life gastrointestinal health and disease: from bench to bedside

Introduction: At birth, the gastrointestinal (GI) tract is colonized by a complex community of microorganisms, forming the basis of the gut microbiome. The gut microbiome plays a fundamental role in host health, disorders of which can lead to an array of GI diseases, both short and long term. Pediatric GI diseases are responsible for significant morbidity and mortality, but many remain poorly understood. Recent advancements in high-throughput technologies have enabled deeper profiling of GI morbidities. Technologies, such as metagenomics, transcriptomics, proteomics and metabolomics, have already been used to identify associations with specific pathologies, and highlight an exciting area of research. However, since these diseases are often complex and multifactorial by nature, reliance on a single experimental approach may not capture the true biological complexity. Therefore, multi-omics aims to integrate singular omic data to further enhance our understanding of disease.Areas covered: This review will discuss and provide an overview of the main omic technologies that are used to study complex GI pathologies in early life.Expert opinion: Multi-omic technologies can help to unravel the complexities of several diseases during early life, aiding in biomarker discovery and enabling the development of novel therapeutics and augment predictive models.

Bifidobacterium breve BBG-001 and intestinal barrier function in preterm babies: Exploratory Studies from the PiPS Trial

BACKGROUND

Uncertainty remains about the role of probiotics to prevent necrotising enterocolitis (NEC) some of which arises from the variety of probiotic interventions used in different trials, many with no prior evidence of potential efficacy. Mechanistic studies of intestinal barrier function embedded in a large probiotic trial could provide evidence about which properties of probiotics might be important for NEC prevention thus facilitating identification of strains with therapeutic potential.

METHODS

Intestinal permeability, stool microbiota, SCFAs and mucosal inflammation were assessed from the second postnatal week in babies enrolled to a randomised controlled trial of B. breve BBG-001 (the PiPS trial). Results were compared by allocation and by stool colonisation with the probiotic.

RESULTS

Ninety-four preterm babies were recruited across six nested studies. B. breve BBG-001 content was higher by allocation and colonisation; Enterobacteriaceae and acetic acid levels were higher by colonisation. No measure of intestinal barrier function showed differences. The PiPS trial found no evidence of efficacy to reduce NEC.

CONCLUSIONS

That the negative results of the PiPS trial were associated with failure of this probiotic to modify intestinal barrier function supports the possibility that the tests described here have the potential to identify strains to progress to large clinical trials.

IMPACT

Uncertainty about the therapeutic role of probiotics to prevent necrotising enterocolitis is in part due to the wide range of bacterial strains with no previous evidence of efficacy used in clinical trials. We hypothesised that mechanistic studies embedded in a probiotic trial would provide evidence about which properties of probiotics might be important for NEC prevention. The finding that the probiotic strain tested, Bifidobacterium breve BBG-001, showed neither effects on intestinal barrier function nor clinical efficacy supports the possibility that these tests have the potential to identify strains to progress to large clinical trials.

Role of cesarean section in the development of neonatal gut microbiota: A systematic review

Background

The delivery mode is one of the factors affecting the type of colonization of the human gut. Gut colonization affects all stages of the human life cycle, and the type of gut microbiome can contribute to immune system function, the development of some diseases, and brain development; and it has a significant impact on a newborn’s growth and development.

Methods

Terms defined as MeSH keywords were searched by the databases, and web search engines such as PubMed, ClinicalTrials.gov, Embase, Scopus, ProQuest, Web of Science, and Google Scholar were searched between 2010 and 2020. The quality of each study was assessed according to the Newcastle–Ottawa scale, and seven eligible and high-quality studies were analyzed.

Finding

The abundances of Bacteroides and Bifidobacterium during the first 3 months of life; Lactobacillus and Bacteroides during the second 3 months of life; Bacteroides and Bifidobacterium during the second 6 months of life; and Bacteroides, Enterobacter, and Streptococcus after the first year of life were higher in vaginal delivery-born infants. While infants born by cesarean section (CS) had higher abundances of Clostridium and Lactobacillus during the first 3 months of life, Enterococcus and Clostridium during the second 3 months of life, and Lactobacillus and Staphylococcus after the first year of life.

Discussion

Delivery mode can affect the type of the human intestinal microbiota. The CS-born babies had lower colonization rates of Bifidobacterium and Bacteroides, but they had higher colonization rates of Clostridium, Lactobacillus, Enterobacter, Enterococcus, and Staphylococcus. Given the effect of microbiota colonization on neonatal health, it is therefore recommended to conduct further studies in order to investigate the effect of the colonization on the delivery mode and on baby’s growth and development.

Application to practice

The aim of this study was to investigate the role of CS in the development of the neonatal gut microbiota.

Lactobacillus reuteri in Its Biofilm State Improves Protection from Experimental Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is a devastating disease predominately found in premature infants that is associated with significant morbidity and mortality. Despite decades of research, medical management with broad spectrum antibiotics and bowel rest has remained relatively unchanged, with no significant improvement in patient outcomes. The etiology of NEC is multi-factorial; however, gastrointestinal dysbiosis plays a prominent role in a neonate's vulnerability to and development of NEC. Probiotics have recently emerged as a new avenue for NEC therapy. However, current delivery methods are associated with potential limitations, including the need for at least daily administration in order to obtain any improvement in outcomes. We present a novel formulation of enterally delivered probiotics that addresses the current limitations. A single enteral dose of Lactobacillus reuteri delivered in a biofilm formulation increases probiotic survival in acidic gastric conditions, increases probiotic adherence to gastrointestinal epithelial cells, and reduces the incidence, severity, and neurocognitive sequelae of NEC in experimental models.

Methods for exploring the faecal microbiome of premature infants: a review

The premature infant gut microbiome plays an important part in infant health and development, and recognition of the implications of microbial dysbiosis in premature infants has prompted significant research into these issues. The approaches to designing investigations into microbial populations are many and varied, each with its own benefits and limitations. The technique used can influence results, contributing to heterogeneity across studies. This review aimed to describe the most common techniques used in researching the preterm infant microbiome, detailing their various limitations. The objective was to provide those entering the field with a broad understanding of available methodologies, so that the likely effects of their use can be factored into literature interpretation and future study design. We found that although many techniques are used for characterising the premature infant microbiome, 16S rRNA short amplicon sequencing is the most common. 16S rRNA short amplicon sequencing has several benefits, including high accuracy, discoverability and high throughput capacity. However, this technique has limitations. Each stage of the protocol offers opportunities for the injection of bias. Bias can contribute to variability between studies using 16S rRNA high throughout sequencing. Thus, we recommend that the interpretation of previous results and future study design be given careful consideration.

The association between enteric viruses and necrotizing enterocolitis

Studies on necrotizing enterocolitis (NEC) have not largely focused on enteric viruses. In order to demonstrate the association between enteric viruses and NEC, stool specimens of 51 neonates with NEC and 39 "normal" neonates were collected to detect rotavirus (RV), astrovirus (ASV), sapovirus, enterovirus (EV), adenovirus (ADV), Epstein-Barr virus (EBV), cytomegalovirus (CMV), and human bocavirus (HBoV). Rotavirus A (RVA), ASV, EBV, and ADV were detected in both the NEC and control groups; however, EV and HBoV were detected only in the NEC group and CMV was not detected in either group. ASV was the most common enteric virus, but no significant differences were found between NEC and control groups, as was similarly the case for EBV and EV. The prevalence of ADV and HBoV was higher in the NEC group than in the control group (P = 0.011, P = 0.005, respectively) but RVA showed the opposite trend (P = 0.014). Virus positivity or negativity had no influence on the clinical manifestation of NEC.Conclusion: The roles of different viruses in NEC are not congruent. Some, such as ASV, may be regarded as commensal in neonates, while in NEC patients, the presence of ADV and EBV may be related to severity of disease. What is known: • The etiology of NEC remains unknown. Studies on necrotizing enterocolitis (NEC) have not largely focused on enteric viruses and the conclusions were inconsistent. What is new: • Enteric viruses are common in the gut of neonates, but not all of them are pathogenic. • The existence of ADV and EBV may be related to the severity of NEC.

Incidence of necrotising enterocolitis before and after introducing routine prophylactic Lactobacillus and Bifidobacterium probiotics

OBJECTIVE

To compare rates of necrotising enterocolitis (NEC), late-onset sepsis, and mortality in 5-year epochs before and after implementation of routine daily multistrain probiotics administration in high-risk neonates.

DESIGN

Single-centre retrospective observational study over the 10-year period from 1 January 2008 to 31 December 2017.

SETTING

Level 3 neonatal intensive care unit (NICU) of the Norfolk and Norwich University Hospital, UK.

PATIENTS

Preterm neonates at high risk of NEC: admitted to NICU within 3 days of birth at <32 weeks' gestation or at 32-36 weeks' gestation and of birth weight <1500 g.

INTERVENTION

Prior to 1 January 2013 probiotics were not used. Thereafter, dual-species Lactobacillus acidophilus and Bifidobacterium bifidum combination probiotics were routinely administered daily to high-risk neonates; from April 2016 triple-species probiotics (L. acidophilus, B. bifidum, and B. longum subspecies infantis) were used.

MAIN OUTCOME MEASURES

Incidence of NEC (modified Bell's stage 2a or greater), late-onset sepsis, and mortality.

RESULTS

Rates of NEC fell from 7.5% (35/469 neonates) in the pre-implementation epoch to 3.1% (16/513 neonates) in the routine probiotics epoch (adjusted sub-hazard ratio=0.44, 95% CI 0.23 to 0.85, p=0.014). The more than halving of NEC rates after probiotics introduction was independent of any measured covariates, including breast milk feeding rates. Cases of late-onset sepsis fell from 106/469 (22.6%) to 59/513 (11.5%) (p<0.0001), and there was no episode of sepsis due to Lactobacillus or Bifidobacterium. All-cause mortality also fell in the routine probiotics epoch, from 67/469 (14.3%) to 47/513 (9.2%), although this was not statistically significant after multivariable adjustment (adjusted sub-hazard ratio=0.74, 95% CI 0.49 to 1.12, p=0.155).

CONCLUSIONS

Administration of multispecies Lactobacillus and Bifidobacterium probiotics has been associated with a significantly decreased risk of NEC and late-onset sepsis in our neonatal unit, and no safety issues. Our data are consistent with routine use of Lactobacillus and Bifidobacterium combination probiotics having a beneficial effect on NEC prevention in very preterm neonates.

The Human Microbiome, Conventional Medicine, and Homeopathy

Human health is intimately linked to the ecology and diversity of the human microbiome. Together, the human organism and the human microbiome work as a complex super-organism throughout the human life cycle. Microbiome science provides direct evidence and substantiation of the fundamental principles of homeopathy, including holism, psychosomatics, direction of cure, the Law of Similars, individuality and susceptibility, minimum dose, and homeostasis. Whilst many conventional (allopathic) medical treatments irreversibly damage the ecology of the microbiome and trigger chronic immune dysfunction and inflammation, the future sustainability of the entire field of medicine depends on the ability to recognize these inconvenient biological truths and to embrace a safer approach based on this evidence. Fortunately, one of the oldest forms of clinically verifiable, evidence-based, and ecologically sustainable medicine, that does not harm the microbiome, already exists in the form of homeopathy.

The Evolving Microbiome from Pregnancy to Early Infancy: A Comprehensive Review

Pregnancy induces a number of immunological, hormonal, and metabolic changes that are necessary for the mother to adapt her body to this new physiological situation. The microbiome of the mother, the placenta and the fetus influence the fetus growth and undoubtedly plays a major role in the adequate development of the newborn infant. Hence, the microbiome modulates the inflammatory mechanisms related to physiological and pathological processes that are involved in the perinatal progress through different mechanisms. The present review summarizes the actual knowledge related to physiological changes in the microbiota occurring in the mother, the fetus, and the child, both during neonatal period and beyond. In addition, we approach some specific pathological situations during the perinatal periods, as well as the influence of the type of delivery and feeding.

Colonisation of the proximal intestinal remnant in newborn infants with enterostomy: a longitudinal study protocol

INTRODUCTION

The gut microbiota plays a main role in the maintenance of host's health. Exposure to different conditions in early life contributes to distinct 'pioneer' bacterial communities in the intestine, which shape the newborn infant development. Newborn infants with congenital malformations of the gastrointestinal tract (CMGIT), necrotising enterocolitis (NEC) and spontaneous intestinal perforation (SIP) commonly require abdominal surgery and enterostomy. The knowledge about the colonisation of these newborns' intestine by microorganisms is scarce. This protocol is designed to explore the microbial colonisation over time of the proximal intestinal remnant in newborn infants who underwent surgery for CMGIT, NEC or SIP and require enterostomy.

METHODS AND ANALYSIS

The literature about microbiota colonisation in newborn infants with enterostomy was reviewed and an observational, longitudinal, prospective study was designed. The infants will be recruited at the Neonatal Intensive Care Unit of the Hospital Dona Estefânia, Centro Hospitalar Universitário de Lisboa Central. Samples of the enterostomy effluent will be collected every 3 days, through 21 days after the first collection. The microorganisms colonising the proximal intestinal remnant will be identified using the 16S rRNA sequence analysis and a subset of microorganisms will be quantified using real-time PCR. This protocol may serve as basis for future observational and interventional studies on the modulation of the intestinal microbiota (eg, probiotics) on short and long-term outcomes in this population.

ETHICS AND DISSEMINATION

This study protocol was approved by the Ethics Committee of Centro Hospitalar Universitário de Lisboa Central (441/2017) and by the Ethics Committee of NOVA Medical School, Universidade Nova de Lisboa (n°50/2018/CEFCM). The results will be spread through peer-reviewed publications and presentations at international scientific meetings.

TRIAL REGISTRATION NUMBER

NCT03340259.

Early enteral feeding in preterm infants

Early enteral feeding is a potentially modifiable risk factor for necrotising enterocolitis (NEC) and late onset sepsis (LOS), however enteral feeding practices for preterm infants are highly variable. High-quality evidence is increasingly available to guide early feeding in preterm infants. Meta-analyses of randomised trials indicate that early trophic feeding within 48 h after birth and introduction of progressive enteral feeding before 4 days of life at an advancement rate above 24 ml/kg/day can be achieved in clinically stable very preterm and very low birthweight (VLBW) infants, without higher mortality or incidence of NEC. This finding may not be generalisable to high risk infants such as those born small for gestational age (SGA) or following absent/reversed end diastolic flow velocity (AREDFV) detected antenatally on placental Doppler studies, due to the small number of such infants in existing trials. Trials targeting such high-risk preterm infants have demonstrated that progressive enteral feeding started in the first 4 days is safe and does not lead to higher NEC or mortality; however, there is a paucity of data to guide feeding advancement in such infants. There is little trial evidence to support bolus or continuous gavage feeding as being superior in clinically stable preterm infants. Trials that examine enteral feeding are commonly unblinded for technical and practical reasons, which increases the risk of bias in such trials, specifically when considering potentially subjective outcome such as NEC and LOS; future clinical trials should focus on objective, primary outcome measures such as all-cause mortality, long term growth and neurodevelopment. Alternatively, important short-term outcomes such as NEC could be used with blinded assessment.

The role of the preterm intestinal microbiome in sepsis and necrotising enterocolitis

Late-onset sepsis (LOS) and necrotising enterocolitis (NEC) account for the highest number of deaths in premature infants and often cause severe morbidity in survivors. NEC is an inflammatory mediated condition, but its pathophysiology remains poorly understood. There is increasing evidence that in LOS the causative organism most often translocates from the gut. No causative microorganism has been consistently associated with either LOS or NEC, but an aberrant gut microbiome development could play a pivotal role. A low bacterial diversity and a delay in anaerobic bacteria colonization may predispose preterm infants to disease development. Conversely, a predominance of Bifidobacterium species and breast milk feeding might help to prevent disease onset. With numerous studies reporting conflicting results, further research is needed to better understand the role of microorganisms and type of feeding in the health status of preterm infants.

Impact of Early Life Antibiotic Exposure and Neonatal Hyperoxia on the Murine Microbiome and Lung Injury

Cross talk between the intestinal microbiome and the lung and its role in lung health remains unknown. Perinatal exposure to antibiotics disrupts the neonatal microbiome and may have an impact on the preterm lung. We hypothesized that perinatal antibiotic exposure leads to long-term intestinal dysbiosis and increased alveolar simplification in a murine hyperoxia model. Pregnant C57BL/6 wild type dams and neonatal mice were treated with antibiotics before and/or immediately after delivery. Control mice received phosphate-buffered saline (PBS). Neonatal mice were exposed to 95% oxygen for 4 days or room air. Microbiome analysis was performed using 16S rRNA gene sequencing. Pulmonary alveolarization and vascularization were analyzed at postnatal day (PND) 21. Perinatal antibiotic exposure modified intestinal beta diversity but not alpha diversity in neonatal mice. Neonatal hyperoxia exposure altered intestinal beta diversity and relative abundance of commensal bacteria in antibiotic treated mice. Hyperoxia disrupted pulmonary alveolarization and vascularization at PND 21; however, there were no differences in the degree of lung injury in antibiotic treated mice compared to vehicle treated controls. Our study suggests that exposure to both hyperoxia and antibiotics early in life may cause long-term alterations in the intestinal microbiome, but intestinal dysbiosis may not significantly influence neonatal hyperoxic lung injury.

Feeding practice influences gut microbiome composition in very low birth weight preterm infants and the association with oxidative stress: A prospective cohort study

Knowledge about the development of the preterm infant gut microbiota is emerging and is critical to their health. Very-low-birth-weight (VLBW; birth weight, <1500 g) infants usually have special dietary needs while showing increased oxidative stress related to intensive care. This prospective cohort study assessed the effect of feeding practice on gut microbiome development and oxidative stress in preterm infants. Fecal samples were collected from each infant in the early (1-2 weeks of enteral feeding) and late (2-4 weeks of enteral feeding) feeding stages. We performed high-throughput sequencing of V3-V4 regions of the 16S rRNA gene to analyze the fecal microbiome composition of 20 VLBW preterm infants and to determine the association of gut bacterial composition with feeding practice using an oxidative stress marker (urinary F2-isoprostane). Our results showed that feeding practices in the late stage significantly influenced the gut microbiome composition and oxidative stress in preterm infants. Preterm infants fed human milk + human milk fortifier and only formula diets showed a significant increase in F2-isoprostane levels (P < 0.05) compared with those fed human milk + formula diet. The gut microbiome of the infants fed the human milk + Human milk fortifier diet showed the lower relative abundance of Veillonella (P < 0.05) compared with that of the infants fed the human milk + formula diet. The gut microbiome of the infants fed the only formula diet showed the lowest microbial diversity and the highest relative abundance of Terrisporobacter (P < 0.05) compared with the gut microbiome of the infants fed the other diets. Correlation network analysis showed that urinary F2-isoprostane level was positively correlated with Terrisporobacter and Enterobacteriaceae abundance (P < 0.05) in the preterm infants. In conclusion, these data suggest that feeding practice affects the bacterial diversity and composition in the gut microbiome and is associated with oxidative stress in VLBW preterm infants.

The Influence of Early Nutrition on Brain Growth and Neurodevelopment in Extremely Preterm Babies: A Narrative Review

Extremely preterm babies are at increased risk of less than optimal neurodevelopment compared with their term-born counterparts. Optimising nutrition is a promising avenue to mitigate the adverse neurodevelopmental consequences of preterm birth. In this narrative review, we summarize current knowledge on how nutrition, and in particular, protein intake, affects neurodevelopment in extremely preterm babies. Observational studies consistently report that higher intravenous and enteral protein intakes are associated with improved growth and possibly neurodevelopment, but differences in methodologies and combinations of intravenous and enteral nutrition strategies make it difficult to determine the effects of each intervention. Unfortunately, there are few randomized controlled trials of nutrition in this population conducted to determine neurodevelopmental outcomes. Substantial variation in reporting of trials, both of nutritional intakes and of outcomes, limits conclusions from meta-analyses. Future studies to determine the effects of nutritional intakes in extremely preterm babies need to be adequately powered to assess neurodevelopmental outcomes separately in boys and girls, and designed to address the many potential confounders which may have clouded research findings to date. The development of minimal reporting sets and core outcome sets for nutrition research will aid future meta-analyses.

Preterm infants have distinct microbiomes not explained by mode of delivery, breastfeeding duration or antibiotic exposure

Background

Preterm infants have low gut microbial diversity and few anaerobes. It is unclear whether the low diversity pertains to prematurity itself or is due to differences in delivery mode, feeding mode or exposure to antibiotics.

Methods

The Norwegian Microbiota Study (NoMIC) was established to examine the colonization of the infant gut and health outcomes. 16S rRNA gene Illumina amplicon-sequenced samples from 519 children (160 preterms), collected at 10 days, 4 months and 1 year postnatally, were used to calculate alpha diversity. Short-chain fatty acids (SCFA) were analysed with gas chromatography and quantified using flame ionization detection. We regressed alpha diversity on gestational age, taking into account possible confounding and mediating factors, such as breastfeeding and antibiotics. Taxonomic differences were tested using Analysis of Composition of Microbiomes (ANCOM) and SCFA profile (as a functional indicator of the microbiota) was tested by Wilcoxon rank-sum.

Results

Preterm infants had 0.45 Shannon units lower bacterial diversity at 10 days postnatally compared with infants born at term (95% confidence interval: -0.60, -0.32). Breastfeeding status and antibiotic exposure were not significant mediators of the gestational age-diversity association, although time spent in the neonatal intensive care unit was. Vaginally born, exclusively breastfed preterm infantss not exposed to antibiotics at 10 days postnatally had fewer Firmicutes and more Proteobacteria than children born at term and an SCFA profile indicating lower saccharolytic fermentation.

Conclusions

Preterm infants had distinct gut microbiome composition and function in the early postnatal period, not explained by factors more common in preterms, such as shorter breastfeeding duration, more antibiotics or caesarean delivery.

Changes of intestinal microbiota in early life

There is an increasing evidence that the intestinal microbiota plays a pivotal role in the maturation of the immune system and in the prevention of diseases occurring during the neonatal period, childhood, and adulthood. A number of nonphysiological conditions during the perinatal period (i.e. caesarean section, prolonged hospitalization, formula feeding, low gestational age) may negatively affect the normal development of the microbiota, leading to decreased amounts of lactobacilli and bifidobacteria and increased amounts of Clostridia. In addition, perinatal antibiotics can cause intestinal dysbiosis that has been associated with short- and long-term diseases. For example, prolonged early empiric antibiotics increase the risk of necrotizing enterocolitis (NEC) and late-onset sepsis (LOS) in preterm neonates, whereas the administration of intrapartum antibiotic prophylaxis (IAP) has been associated with inflammatory bowel diseases, obesity, and atopic conditions, such as eczema and wheezing. Promoting breastfeeding, reducing the length of hospital stay, and reducing unnecessary antibiotic therapies are useful strategies to counterbalance unintended effects of these conditions.

An enhanced Lactobacillus reuteri biofilm formulation that increases protection against experimental necrotizing enterocolitis

One significant drawback of current probiotic therapy for the prevention of necrotizing enterocolitis (NEC) is the need for at least daily administration because of poor probiotic persistence after enteral administration, increasing the risk of the probiotic bacteria causing bacteremia or sepsis if the intestines are already compromised. We previously showed that the effectiveness of Lactobacillus reuteri ( Lr) in preventing NEC is enhanced when Lr is grown as a biofilm on the surface of dextranomer microspheres (DM). Here we sought to test the efficacy of Lr administration by manipulating the Lr biofilm state with the addition of biofilm-promoting substances (sucrose and maltose) to DM or by mutating the Lr gtfW gene (encoding an enzyme central to biofilm production). Using an animal model of NEC, we determined that Lr adhered to sucrose- or maltose-loaded DM significantly reduced histologic injury, improved host survival, decreased intestinal permeability, reduced intestinal inflammation, and altered the gut microbiome compared with Lr adhered to unloaded DM. These effects were abolished when DM or GtfW were absent from the Lr inoculum. This demonstrates that a single dose of Lr in its biofilm state decreases NEC incidence. Importantly, preloading DM with sucrose or maltose further enhances Lr protection against NEC in a GtfW-dependent fashion, demonstrating the tunability of the approach and the potential to use other cargos to enhance future probiotic formulations. NEW & NOTEWORTHY Previous clinical trials of probiotics to prevent necrotizing enterocolitis have had variable results. In these studies, probiotics were delivered in their planktonic, free-living form. We have developed a novel probiotic delivery system in which Lactobacillus reuteri (Lr) is delivered in its biofilm state. In a model of experimental necrotizing enterocolitis, this formulation significantly reduces intestinal inflammation and permeability, improves survival, and preserves the natural gut microflora compared with the administration of Lr in its free-living form.

Does antibiotic choice for the treatment of suspected late-onset sepsis in premature infants determine the risk of developing necrotising enterocolitis? A systematic review

BACKGROUND

Necrotising enterocolitis (NEC) is a significant cause of infant morbidity and mortality, disproportionately affecting those of extreme prematurity and/or very low birth weight. A number of risk factors have been identified, including an association between the use of antibiotics, and the subsequent development of NEC.

AIM

This review sought to address whether the choice of antibiotic(s) used to treat infants with suspected late-onset sepsis (LOS) influences the risk of developing NEC.

METHODS

A systematic review was performed across Web of Knowledge, Cochrane Library, Ovid Medline, EMBASE and CINAHL databases, up to February 2018, assessing the primary outcome of NEC occurrence, as extracted directly from the published articles. Studies were included if they were randomised control trials (or featured adequate adjustment for confounders); included clear criteria for defining LOS/NEC; and assessed occurrence of NEC in premature infants treated for LOS with intravenous antibiotics. Studies were excluded if non-original, not exclusively featuring premature infants, or where treatment was given for early-onset sepsis only.

FINDINGS

2291 titles and abstracts were identified, of which one study (81 subjects) was suitable for analysis, following screening against eligibility criteria. This suggested a decreased risk of developing definite NEC following treatment with a vancomycin/aztreonam combination, versus a vancomycin/gentamicin regimen (OR = 0·08, 95%CI = 0·00-1·45).

CONCLUSION

This systematic review identified one study where the occurrence of NEC was reported in the context of comparing different antibiotic regimens for late onset sepsis and highlights that the type of antibiotic used to treat LOS in preterm infants might be a determinant of the risk of developing NEC. Although it is known that different antibiotic combinations impact the enteric microbiome and that antibiotic exposure is a risk factor for NEC, there is a paucity of well-designed studies that look at the relationship between NEC risk and specific antibiotic exposures.

Altered intestinal microbiota composition, antibiotic therapy and intestinal inflammation in children and adolescents with cystic fibrosis

The aim of the present study was to evaluate the effect of cystic fibrosis and antibiotic therapy on intestinal microbiota composition and intestinal inflammation in children and adolescents. A cross-sectional controlled study was conducted with 36 children and adolescents: 19 in the cystic fibrosis group (CFG) and 17 in the control group (CG) matched for age and sex. The CFG was subdivided based on the use of antibiotic therapy (CFAB group) and non-use of antibiotic therapy (CFnAB group). The following data were evaluated: colonization, antibiotic therapy, mutation, breastfeeding, use of infant formula, type of delivery, introduction of solid foods, body mass index, fecal calprotectin and intestinal microbiota composition (fluorescence in situ hybridization). Intestinal inflammation evaluated by fecal calprotectin was significantly higher in the CFG (median: 40.80 µg/g, IQR: 19.80-87.10, p = 0.040) and CFAB group (median: 62.95 µg/g, IQR: 21.80-136.62, p = 0.045) compared to the CG (median: 20.15 µg/g, IQR: 16.20-31.00), and the Bacteroides, Firmicutes, Eubacterium rectale and Faecalibacterium prausnitzii were significantly decreased (p < 0.05) in the CFG compared to the CG, whereas the bacteria Clostridium difficile, Escherichia coli and Pseudomonas aeruginosa were significantly increased in the CFG (p < 0.05). The main differences were found between the CG and CFAB group for Eubacterium rectale (p = 0.006), Bifidobacterium (p = 0.017), Escherichia coli (p = 0.030), Firmicutes (p = 0.002), Pseudomonas aeruginosa (p < 0.001) and Clostridium difficile (p = 0.006). The results of this study confirm intestinal inflammation in patients with CF, which may be related to changes in the composition of the intestinal microbiota.

Changes of intestinal microbiota composition and diversity in very low birth weight infants related to strategies of NEC prophylaxis: protocol for an observational multicentre pilot study

Background

At the Division of Neonatology, Department of Paediatrics, Medical University Graz, a unique regimen of necrotizing enterocolitis (NEC) prophylaxis in preterm infants showing a < 1500 g birth weight (i.e. very low birth weight, VLBW) is used. The regimen includes oral antibiotic and antifungal therapy and probiotic preparations as well as a standardised feeding regimen. The incidence of NEC in preterm infants treated by this regimen has been shown to be lower, reflecting 0.7% when treatment was initiated on the first day of life, compared to international incidence rates (5.1%). However, the impact of the prophylaxis regimen on the intestinal microbiome is yet unknown.

Methods

We here report the protocol of an observational multicentre STROBE compliant pilot study in VLBW preterm infants. Research will compare three groups as defined by different NEC prophylaxis regimens. Each centre will provide 20 infants. Stool samples will be collected every 2 days throughout the first 2 weeks of life. Samples will be stored at − 80 °C until 16S-rRNA sequencing. 16S-rRNA genes will be amplified using suitable primers (specific for bacteria, fungi and archaea) and prepared for MiSeq Sequencing. Analyses will be performed using public analysis-pipelines, such as Mothur and Qiime, thus allowing an analysis of high-throughput community sequencing data. Abundance and composition changes in intestinal microbiota will be compared between the groups throughout the first 2 weeks of life.

Discussion

Different surroundings at the three participating study centres, including contacts to care takers and parents, as well as feeding or medication all might influence intestinal microbiota composition and abundance. In the planned sequel study, this should be kept in mind and a more standardised process ought to be established. However, the results obtained from the presented pilot study will display the burden of bias and help to establish a more strict protocol for the future.

Trial registration

Trial has been registered with the German Registry for Clinical Trials (registry ID DRKS00009290).

Electronic supplementary material

The online version of this article (10.1186/s40814-017-0195-y) contains supplementary material, which is available to authorized users.

How to feed a baby recovering from necrotising enterocolitis when maternal milk is not available

Necrotising enterocolitis (NEC) is a devastating disease with significant mortality and serious adverse outcomes in at least 50% including short gut and poor neurodevelopment. Research and management are complicated by a lack of robust clinical markers, and without histological confirmation, there is a risk of both underdiagnosis and overdiagnosis. Interunit variations in the thresholds for surgical referral, laparotomy and postmortem rates mean the actual incidence is difficult to determine, especially because the histological term 'NEC' is used in practice to describe a heterogeneous clinical syndrome. In this article, we discuss issues relating to choice of milk feed type following a clinical diagnosis of 'NEC' where mother's own milk is not available. We review common clinical concerns relating to feeding following NEC and the rationale for modifications of the macronutrient composition and quality of formula milk.

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.

Longitudinal development of the gut microbiome and metabolome in preterm neonates with late onset sepsis and healthy controls

BACKGROUND

Late onset sepsis (LOS) in preterm infants is associated with considerable morbidity and mortality. While studies have implicated gut bacteria in the aetiology of the disease, functional analysis and mechanistic insights are generally lacking. We performed temporal bacterial (n = 613) and metabolomic (n = 63) profiling on extensively sampled stool from 7 infants with LOS and 28 matched healthy (no LOS or NEC) controls.

RESULTS

The bacteria isolated in diagnostic blood culture usually corresponded to the dominant bacterial genera in the gut microbiome. Longitudinal changes were monitored based on preterm gut community types (PGCTs), where control infants had an increased number of PGCTs compared to LOS infants (P = 0.011). PGCT 6, characterised by Bifidobacteria dominance, was only present in control infants. Metabolite profiles differed between LOS and control infants at diagnosis and 7 days later, but not 7 days prior to diagnosis. Bifidobacteria was positively correlated with control metabolites, including raffinose, sucrose, and acetic acid.

CONCLUSIONS

Using multi-omic analysis, we show that the gut microbiome is involved in the pathogenesis of LOS. While the causative agent of LOS varies, it is usually abundant in the gut. Bifidobacteria dominance was associated with control infants, and the presence of this organism may directly protect, or act as a marker for protection, against gut epithelial translocation. While the metabolomic data is preliminary, the findings support that gut development and protection in preterm infants is associated with increased in prebiotic oligosaccharides (e.g. raffinose) and the growth of beneficial bacteria (e.g. Bifidobacterium).

Cesarean or Vaginal Birth Does Not Impact the Longitudinal Development of the Gut Microbiome in a Cohort of Exclusively Preterm Infants

The short and long-term impact of birth mode on the developing gut microbiome in neonates has potential implications for the health of infants. In term infants, the microbiome immediately following birth across multiple body sites corresponds to birth mode, with increased Bacteroides in vaginally delivered infants. We aimed to determine the impact of birth mode of the preterm gut microbiome over the first 100 days of life and following neonatal intensive care unit (NICU) discharge. In total, 867 stool samples from 46 preterm infants (21 cesarean and 25 vaginal), median gestational age 27 weeks, were sequenced (V4 region 16S rRNA gene, Illumina MiSeq). Of these, 776 samples passed quality filtering and were included in the analysis. The overall longitudinal alpha-diversity and within infant beta-diversity was comparable between cesarean and vaginally delivered infants. Vaginally delivered infants kept significantly more OTUs from 2 months of life and following NICU discharge, but OTUs lost, gained, and regained were not different based on birth mode. Furthermore, the temporal progression of dominant genera was comparable between birth modes and no significant difference was found for any genera following adjustment for covariates. Lastly, preterm gut community types (PGCTs) showed some moderate differences in very early life, but progressed toward a comparable pattern by week 5. No PGCT was significantly associated with cesarean or vaginal birth. Unlike term infants, birth mode was not significantly associated with changes in microbial diversity, composition, specific taxa, or overall microbial development in preterm infants. This may result from the dominating effects of NICU exposures including the universal use of antibiotics immediately following birth and/or the lack of Bacteroides colonizing preterm infants.

The Effect of Maternal Milk on Tolerance and Growth in Premature Infants: A Hypothesis-generating Study

OBJECTIVE

Early growth rates and feeding advancement rates of preterm infants are thought to influence later health. Feeding advancement is often difficult because of feeding intolerance. Exclusive human milk feeding improves tolerance, but can result in a lower weight gain rate. The addition of human milk fortifier has advantages for growth, but there are concerns that it may nullify the beneficial effect of human milk on tolerance. Therefore, the objective of the present study was to evaluate the relation between the amount of fortified human milk or formula and feeding tolerance and growth in preterm infants.

METHODS

Patients (n = 174) participating in the TOL trial and born with a gestational age 30 weeks or younger were divided into tertiles according to the amount of human milk received during feeding advancement. Data on feeding tolerance during the advancement phase of enteral nutrition and anthropometrics were analysed.

RESULTS

The infants (n = 59) receiving the lowest percentage of their enteral intake as human milk (0%-57%) had the lowest amount of gastric residuals (P = 0.034) compared with the other 2 tertiles. Time to reach full enteral feeding and other tolerance parameters were not different among the groups. There was no dose response effect of the amount of human milk consumed on growth.

CONCLUSIONS

In preterm infants, an association between type of feeding (human milk vs infant formula) and time to achieve full enteral feeding or short-term growth was not found. Future prospective trials are needed to verify our results and focus on means to improve tolerance further.

Mechanisms Affecting the Gut of Preterm Infants in Enteral Feeding Trials

Large randomized controlled trials (RCTs) in preterm infants offer unique opportunities for mechanistic evaluation of the risk factors leading to serious diseases, as well as the actions of interventions designed to prevent them. Necrotizing enterocolitis (NEC) a serious inflammatory gut condition and late-onset sepsis (LOS) are common feeding and nutrition-related problems that may cause death or serious long-term morbidity and are key outcomes in two current UK National Institutes for Health Research (NIHR) trials. Speed of increasing milk feeds trial (SIFT) randomized preterm infants to different rates of increases in milk feeds with a primary outcome of survival without disability at 2 years corrected age. Enteral lactoferrin in neonates (ELFIN) randomizes infants to supplemental enteral lactoferrin or placebo with a primary outcome of LOS. This is a protocol for the mechanisms affecting the gut of preterm infants in enteral feeding trials (MAGPIE) study and is funded by the UK NIHR Efficacy and Mechanistic Evaluation programme. MAGPIE will recruit ~480 preterm infants who were enrolled in SIFT or ELFIN. Participation in MAGPIE does not change the main trial protocols and uses non-invasive sampling of stool and urine, along with any residual resected gut tissue if infants required surgery. Trial interventions may involve effects on gut microbes, metabolites (e.g., short-chain fatty acids), and aspects of host immune function. Current hypotheses suggest that NEC and/or LOS are due to a dysregulated immune system in the context of gut dysbiosis, but mechanisms have not been systematically studied within large RCTs. Microbiomic analysis will use next-generation sequencing, and metabolites will be assessed by mass spectrometry to detect volatile organic and other compounds produced by microbes or the host. We will explore differences between disease cases and controls, as well as exploring the actions of trial interventions. Impacts of this research are multiple: translation of knowledge of mechanisms promoting gut health may explain outcomes or suggest alternate strategies to improve health. Results may identify new non-invasive diagnostic or monitoring techniques, preventative or treatment strategies for NEC or LOS, or provide data useful for risk stratification in future studies. Mechanistic evaluation might be especially informative where there are not clear effects on the primary outcome (ISRCTN 12554594).

Cesarean or Vaginal Birth Does Not Impact the Longitudinal Development of the Gut Microbiome in a Cohort of Exclusively Preterm Infants

The short and long-term impact of birth mode on the developing gut microbiome in neonates has potential implications for the health of infants. In term infants, the microbiome immediately following birth across multiple body sites corresponds to birth mode, with increased Bacteroides in vaginally delivered infants. We aimed to determine the impact of birth mode of the preterm gut microbiome over the first 100 days of life and following neonatal intensive care unit (NICU) discharge. In total, 867 stool samples from 46 preterm infants (21 cesarean and 25 vaginal), median gestational age 27 weeks, were sequenced (V4 region 16S rRNA gene, Illumina MiSeq). Of these, 776 samples passed quality filtering and were included in the analysis. The overall longitudinal alpha-diversity and within infant beta-diversity was comparable between cesarean and vaginally delivered infants. Vaginally delivered infants kept significantly more OTUs from 2 months of life and following NICU discharge, but OTUs lost, gained, and regained were not different based on birth mode. Furthermore, the temporal progression of dominant genera was comparable between birth modes and no significant difference was found for any genera following adjustment for covariates. Lastly, preterm gut community types (PGCTs) showed some moderate differences in very early life, but progressed toward a comparable pattern by week 5. No PGCT was significantly associated with cesarean or vaginal birth. Unlike term infants, birth mode was not significantly associated with changes in microbial diversity, composition, specific taxa, or overall microbial development in preterm infants. This may result from the dominating effects of NICU exposures including the universal use of antibiotics immediately following birth and/or the lack of Bacteroides colonizing preterm infants.

Probiotics for Preterm Infants: A Premature or Overdue Necrotizing Enterocolitis Prevention Strategy?

Common among preterm, very low birth weight (VLBW) and extremely low birth weight (ELBW) infants, necrotizing enterocolitis (NEC) is a gastrointestinal, infectious disease that remains a leading cause of morbidity and mortality among this high-risk population. To combat this devastating condition, research efforts have been redirected from treatment toward prevention strategies. Although there are several proposed risk-reduction strategies, one intervention gaining support is the administration of prophylactic enteral probiotics. Regardless of growing evidentiary support and a benign safety profile, neonatal providers have yet to embrace this therapy. This article provides an overview of the proposed benefits of probiotics, focusing on their role as a NEC prevention strategy. A review of several sentinel research studies targeting preterm, VLBW, and ELBW infants is provided. Considerations for ongoing research are reviewed. Finally, two evidence-based NEC prevention probiotics protocols are presented.

Association between birth route and late-onset sepsis in very preterm neonates

OBJECTIVE

To evaluate the association between birth route and late-onset sepsis (LOS), and coagulase-negative Staphylococcal (CONS)-related LOS in preterm neonates.

STUDY DESIGN

In this observational study, data from 20,038 infants born between 22 and 32 weeks' gestation and admitted to Canadian neonatal intensive care units between 2010 and 2014 were analyzed retrospectively. The impact of birth route on LOS was assessed using univariate analysis and multiple logistic regression.

RESULTS

A total of 8218 neonates were born via vaginal route and 11,820 via cesarean section. Incidence rates of LOS for infants born vaginally and via a cesarean section were 13.1 and 13.2%, respectively, and there was no significant difference in odds of LOS between the groups (adjusted odds ratio (AOR): 0.99; 95% CI 0.87 to 1.12); however, the odds of CONS sepsis were higher in the cesarean group (AOR: 1.15; 95% CI: 1.01 to 1.32).

CONCLUSION

Birth route did not have an impact on LOS, but was associated with CONS-related LOS.

Recent advances in the management of infants born <1000 g

In this review, we survey some significant advances in the medical care of babies <1000 g and we highlight the development of care pathways that ensure optimal antenatal care, which is a prerequisite for good neonatal outcomes. We also suggest that the long overdue development of family integrated care will in the end prove at least as important as the recent medical advances.

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.

Building a Beneficial Microbiome from Birth

The microbiota has recently been recognized as a driver of health that affects the immune, nervous, and metabolic systems. This influence is partially exerted through the metabolites produced, which may be relevant for optimal infant development and health. The gut microbiota begins developing early in life, and this initial colonization is remarkably important because it may influence long-term microbiota composition and activity. Considering that the microbiome may play a key role in health and disease, maintaining a protective microbiota could be critical in preventing dysbiosis-related diseases such as allergies, autoimmunity disorders, and metabolic syndrome. Breast milk and milk glycans in particular are thought to play a major role in shaping the early-life microbiota and promoting its development, thus affecting health. This review describes some of the effects the microbiota has on the host and discusses the role microbial metabolites play in shaping newborn health and development. We describe the gut microbiota structure and function during early life and the factors that determine its composition and hypothesize about the effects of human milk oligosaccharides and other prebiotic fibers on the neonatal microbiota.

Gut Microbiome and Kidney Disease in Pediatrics: Does Connection Exist?

Child development is a unique and continuous process that is impacted by genetics and environmental factors. Gut microbiome changes with development and depends on the stage of gut maturation, nutrition, and overall health. In spite of emerging data and active study in adults, the gut-renal axis in pediatrics has not been well considered and investigated. This review will focus on the current knowledge of gut microbiota impacts on kidney disease with extrapolation to the pediatric population.

The Developing Microbiome of the Preterm Infant

PURPOSE

To determine the importance of the neonatal microbiome in intestinal and overall health.

METHOD

A review of existing literature.

FINDINGS AND IMPLICATIONS

The microbiome is increasingly understood to have a significant role in health and disease. However, the microbiome of the preterm infant is unique, with simple microbial communities exposed to a consistent diet in a regulated environment, and development from naive to stable under the influence of the neonatal intensive care unit. This early microbiome encounters a still developing host and thus has the potential to program fundamental pathways with implications for neonatal and later outcomes.

Metabolomic and proteomic analysis of serum from preterm infants with necrotising entercolitis and late-onset sepsis

BACKGROUND

Necrotising enterocolitis (NEC) and late-onset sepsis (LOS) are the leading causes of death among preterm infants in the developed world. This study aimed to explore the serum proteome and metabolome longitudinally in preterm infants with NEC or LOS, matched to controls.

METHODS

Nineteen patients (10 cases, 9 controls) were included. A sample 14 d prior to and following, as well as at disease diagnosis, was included for cases. Controls had serum matched at diagnosis for corresponding case. All samples (n = 39) underwent shotgun proteomic analysis, and 37 samples also underwent metabolomics analysis using ultra performance liquid chromatography-tandem mass spectrometry.

RESULTS

The proteomic and metabolomic profiles of serum were comparable between all infants. Eight proteins were associated with NEC and four proteins were associated with LOS. C-reactive protein was increased in all NEC patients at diagnosis.

CONCLUSION

No single protein or metabolite was detected in all NEC or LOS cases which was absent from controls; however, several proteins were identified which were associated with disease status. The differing expression of these proteins between diseased infants potentially relates to differing pathophysiology of disease. Thus, it is unlikely a single biomarker exists for NEC and/or LOS.

Effect of Saccharomyces boulardii and Mode of Delivery on the Early Development of the Gut Microbial Community in Preterm Infants

Background

Recent advances in culture-independent approaches have enabled insights into the diversity, complexity, and individual variability of gut microbial communities.

Objectives

To examine the effect of oral administration of Saccharomyces (S.) boulardii and mode of delivery on the intestinal microbial community in preterm infants.

Study Design

Stool samples were collected from preterm newborns randomly divided into two groups: a probiotic-receiving group (n = 18) or a placebo group (n = 21). Samples were collected before probiotic intake (day 0), and after 2 and 6 weeks of supplementation. The composition of colonizing bacteria was assessed by 16S ribosomal RNA (rRNA) gene sequencing of fecal samples using the Ion 16S Metagenomics Kit and the Ion Torrent Personal Genome Machine platform.

Results

A total of 11932257 reads were generated, and were clustered into 459, 187, and 176 operational taxonomic units at 0 days, 2 weeks, and 6 weeks, respectively. Of the 17 identified phyla, Firmicutes Actinobacteria, Proteobacteria, and Bacteroidetes were universal. The microbial community differed at day 0 compared with at 2 weeks and 6 weeks. There was a tendency for increased bacterial diversity at 2 weeks and 6 weeks compared with day 0, and infants with a gestational age of 31 weeks or higher presented increased bacterial diversity prior to S. boulardii administration. Firmicutes and Proteobacteria remained stable during the observation period, whereas Actinobacteria and Bacteroidetes increased in abundance, the latter particularly more sharply in vaginally delivered infants.

Conclusion

While the mode of delivery may influence the development of a microbial community, this study had not enough power to detect statistical differences between cohorts supplemented with probiotics, and in a consequence, to speculate on S. boulardii effect on gut microbiome composition in preterm newborns.

Prevention of Necrotizing Enterocolitis Through Manipulation of the Intestinal Microbiota of the Premature Infant

PURPOSE

In spite of four decades of research, necrotizing enterocolitis (NEC) remains the most common gastrointestinal complication in premature infants with high mortality and long-term morbidity. The composition of the intestinal microbiota of the premature infant differs dramatically from that of the healthy term infant and appears to be an important risk factor for NEC.

METHODS

We review the evidence of an association between intestinal dysbiosis and NEC and summarize published English language clinical trials and cohort studies involving attempts to manipulate the intestinal microbiota in premature infants.

FINDINGS

Promising NEC prevention strategies that alter the intestinal microbiota include probiotics, prebiotics, synbiotics, lacteroferrin, and human milk feeding.

IMPLICATIONS

Shaping the intestinal microbiota of the premature infant through human milk feeding and dietary supplements decreases the risk of NEC. Further studies to identify the ideal microbial composition and the most effective combination of supplements are indicated.

Routine Use of Probiotics in Preterm Infants: Longitudinal Impact on the Microbiome and Metabolome

BACKGROUND

Probiotics are live microbial supplements that colonize the gut and potentially exert health benefit to the host.

OBJECTIVES

We aimed to determine the impact of a probiotic (Infloran®: Lactobacillus acidophilus-NCIMB701748 and Bifidobacterium bifidum-ATCC15696) on the bacterial and metabolic function of the preterm gut while in the neonatal intensive care unit (NICU) and following discharge.

METHODS

Stool samples (n = 88) were collected before, during, and after probiotic intake from 7 patients, along with time-matched controls from 3 patients. Samples were also collected following discharge home from the NICU. Samples underwent bacterial profiling analysis by 16S rRNA gene sequencing and quantitative PCR (qPCR), as well as metabolomic profiling using liquid chromatography mass spectrometry.

RESULTS

Bacterial profiling showed greater Bifidobacterium (15.1%) and Lactobacillus (4.2%) during supplementation compared to the control group (4.0% and 0%, respectively). While Lactobacillus became reduced after the probiotic had been stopped, Bifidobacterium remained high following discharge, suggestive of successful colonisation. qPCR analysis showed a significant increase (p ≤ 0.01) in B. bifidum in infants who received probiotic treatment compared to controls, but no significant increase was observed for L. acidophilus (p = 0.153). Metabolite profiling showed clustering based on receiving probiotic or matched controls, with distinct metabolites associated with probiotic administration.

CONCLUSIONS

Probiotic species successfully colonise the preterm gut, reducing the relative abundance of potentially pathogenic bacteria, and effecting gut functioning. Bifidobacterium (but not Lactobacillus) colonised the gut in the long term, suggesting the possibility that therapeutically administered probiotics may continue to exert important functional effects on gut microbial communities in early infancy.

Cytomegalovirus and other common enteric viruses are not commonly associated with NEC

AIM

Changes in gut microbiota may contribute to NEC, but most studies focus on bacteria. Case reports suggest a link between cytomegalovirus (CMV) or other enteric viruses and NEC, but there are few case series systematically looking at common potential viral causes. We aimed to assess the presence of candidate viruses in blood or stool of a case series of infants with NEC managed in one surgical centre.

METHODS

We identified 22 infants diagnosed with NEC (from November 2011 to March 2014): 17 had suitable blood stored, of whom 14 also had suitable stool samples stored. Blood was analysed with polymerase chain reaction (PCR) for CMV, Epstein-Barr virus (EBV) and adenovirus, and stool by PCR for norovirus, sappovirus, astrovirus, adenovirus and rotavirus.

RESULTS

All samples were negative.

CONCLUSION

Although case reports indicate an episodic association of enteric viruses in NEC, the inability to detect any of these viruses in our 17 NEC infants suggests that a viral aetiology is unlikely to be causative for most sporadic forms of NEC.