Arguments against routine administration of probiotics for NEC prevention

Probiotic supplementation and risk of necrotizing enterocolitis and mortality among extremely preterm infants-the Probiotics in Extreme Prematurity in Scandinavia (PEPS) trial: study protocol for a multicenter, double-blinded, placebo-controlled, and registry-based randomized controlled trial

BACKGROUND

Extremely preterm infants, defined as those born before 28 weeks' gestational age, are a very vulnerable patient group at high risk for adverse outcomes, such as necrotizing enterocolitis and death. Necrotizing enterocolitis is an inflammatory gastrointestinal disease with high incidence in this cohort and has severe implications on morbidity and mortality. Previous randomized controlled trials have shown reduced incidence of necrotizing enterocolitis among older preterm infants following probiotic supplementation. However, these trials were underpowered for extremely preterm infants, rendering evidence for probiotic supplementation in this population insufficient to date.

METHODS

The Probiotics in Extreme Prematurity in Scandinavia (PEPS) trial is a multicenter, double-blinded, placebo-controlled and registry-based randomized controlled trial conducted among extremely preterm infants (n = 1620) born at six tertiary neonatal units in Sweden and four units in Denmark. Enrolled infants will be allocated to receive either probiotic supplementation with ProPrems® (Bifidobacterium infantis, Bifidobacterium lactis, and Streptococcus thermophilus) diluted in 3 mL breastmilk or placebo (0.5 g maltodextrin powder) diluted in 3 mL breastmilk per day until gestational week 34. The primary composite outcome is incidence of necrotizing enterocolitis and/or mortality. Secondary outcomes include incidence of late-onset sepsis, length of hospitalization, use of antibiotics, feeding tolerance, growth, and body composition at age of full-term and 3 months corrected age after hospital discharge.

DISCUSSION

Current recommendations for probiotic supplementation in Sweden and Denmark do not include extremely preterm infants due to lack of evidence in this population. However, this young subgroup is notably the most at risk for experiencing adverse outcomes. This trial aims to investigate the effects of probiotic supplementation on necrotizing enterocolitis, death, and other relevant outcomes to provide sufficiently powered, high-quality evidence to inform probiotic supplementation guidelines in this population. The results could have implications for clinical practice both in Sweden and Denmark and worldwide.

TRIAL REGISTRATION

( Clinicaltrials.gov ): NCT05604846.

Probiotics to prevent necrotising enterocolitis in very preterm or very low birth weight infants

BACKGROUND

Intestinal dysbiosis may contribute to the pathogenesis of necrotising enterocolitis (NEC) in very preterm or very low birth weight (VLBW) infants. Dietary supplementation with probiotics to modulate the intestinal microbiome has been proposed as a strategy to reduce the risk of NEC and associated mortality and morbidity in very preterm or VLBW infants.

OBJECTIVES

To determine the effect of supplemental probiotics on the risk of NEC and associated mortality and morbidity in very preterm or very low birth weight infants.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, the Maternity and Infant Care database, and CINAHL from inception to July 2022. We searched clinical trials databases and conference proceedings, and examined the reference lists of retrieved articles.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs comparing probiotics with placebo or no probiotics in very preterm infants (born before 32 weeks' gestation) and VLBW infants (weighing less than 1500 g at birth).

DATA COLLECTION AND ANALYSIS

Two review authors independently evaluated risk of bias of the trials, extracted data, and synthesised effect estimates using risk ratios (RRs), risk differences (RDs), and mean differences (MDs), with associated 95% confidence intervals (CIs). The primary outcomes were NEC and all-cause mortality; secondary outcome measures were late-onset invasive infection (more than 48 hours after birth), duration of hospitalisation from birth, and neurodevelopmental impairment. We used the GRADE approach to assess the certainty of the evidence.

MAIN RESULTS

We included 60 trials with 11,156 infants. Most trials were small (median sample size 145 infants). The main potential sources of bias were unclear reporting of methods for concealing allocation and masking caregivers or investigators in about half of the trials. The formulation of the probiotics varied across trials. The most common preparations contained Bifidobacterium spp., Lactobacillus spp., Saccharomyces spp., andStreptococcus spp., alone or in combination. Very preterm or very low birth weight infants Probiotics may reduce the risk of NEC (RR 0.54, 95% CI 0.46 to 0.65; I² = 17%; 57 trials, 10,918 infants; low certainty). The number needed to treat for an additional beneficial outcome (NNTB) was 33 (95% CI 25 to 50). Probiotics probably reduce mortality slightly (RR 0.77, 95% CI 0.66 to 0.90; I² = 0%; 54 trials, 10,484 infants; moderate certainty); the NNTB was 50 (95% CI 50 to 100). Probiotics probably have little or no effect on the risk of late-onset invasive infection (RR 0.89, 95% CI 0.82 to 0.97; I² = 22%; 49 trials, 9876 infants; moderate certainty). Probiotics may have little or no effect on neurodevelopmental impairment (RR 1.03, 95% CI 0.84 to 1.26; I² = 0%; 5 trials, 1518 infants; low certainty). Extremely preterm or extremely low birth weight infants Few data were available for extremely preterm or extremely low birth weight (ELBW) infants. In this population, probiotics may have little or no effect on NEC (RR 0.92, 95% CI 0.69 to 1.22, I² = 0%; 10 trials, 1836 infants; low certainty), all-cause mortality (RR 0.92, 95% CI 0.72 to 1.18; I² = 0%; 7 trials, 1723 infants; low certainty), or late-onset invasive infection (RR 0.93, 95% CI 0.78 to 1.09; I² = 0%; 7 trials, 1533 infants; low certainty). No trials provided data for measures of neurodevelopmental impairment in extremely preterm or ELBW infants.

AUTHORS' CONCLUSIONS

Given the low to moderate certainty of evidence for the effects of probiotic supplements on the risk of NEC and associated morbidity and mortality for very preterm or VLBW infants, and particularly for extremely preterm or ELBW infants, there is a need for further large, high-quality trials to provide evidence of sufficient validity and applicability to inform policy and practice.

Prebiotics to prevent necrotising enterocolitis in very preterm or very low birth weight infants

BACKGROUND

Dietary supplementation with prebiotic oligosaccharides to modulate the intestinal microbiome has been proposed as a strategy to reduce the risk of necrotising enterocolitis (NEC) and associated mortality and morbidity in very preterm or very low birth weight (VLBW) infants.

OBJECTIVES

To assess the benefits and harms of enteral supplementation with prebiotics (versus placebo or no treatment) for preventing NEC and associated morbidity and mortality in very preterm or VLBW infants.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, the Maternity and Infant Care database and the Cumulative Index to Nursing and Allied Health Literature (CINAHL), from the earliest records to July 2022. We searched clinical trials databases and conference proceedings, and examined the reference lists of retrieved articles.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs comparing prebiotics with placebo or no prebiotics in very preterm (< 32 weeks' gestation) or VLBW (< 1500 g) infants. The primary outcomes were NEC and all-cause mortality, and the secondary outcomes were late-onset invasive infection, duration of hospitalisation since birth, and neurodevelopmental impairment.

DATA COLLECTION AND ANALYSIS

Two review authors separately evaluated risk of bias of the trials, extracted data, and synthesised effect estimates using risk ratio (RR), risk difference (RD), and mean difference (MD), with associated 95% confidence intervals (CIs). The primary outcomes of interest were NEC and all-cause mortality; our secondary outcome measures were late-onset (> 48 hours after birth) invasive infection, duration of hospitalisation, and neurodevelopmental impairment. We used the GRADE approach to assess the level of certainty of the evidence.

MAIN RESULTS

We included seven trials in which a total of 705 infants participated. All the trials were small (mean sample size 100). Lack of clarity on methods to conceal allocation and mask caregivers or investigators were potential sources of bias in three of the trials. The studied prebiotics were fructo- and galacto-oligosaccharides, inulin, and lactulose, typically administered daily with enteral feeds during birth hospitalisation. Meta-analyses of data from seven trials (686 infants) suggest that prebiotics may result in little or no difference in NEC (RR 0.97, 95% CI 0.60 to 1.56; RD none fewer per 1000, 95% CI 50 fewer to 40 more; low-certainty evidence), all-cause mortality (RR 0.43, 95% CI 0.20 to 0.92; 40 per 1000 fewer, 95% CI 70 fewer to none fewer; low-certainty evidence), or late-onset invasive infection (RR 0.79, 95% CI 0.60 to 1.06; 50 per 1000 fewer, 95% CI 100 fewer to 10 more; low-certainty evidence) prior to hospital discharge. The certainty of this evidence is low because of concerns about the risk of bias in some trials and the imprecision of the effect size estimates. The data available from one trial provided only very low-certainty evidence about the effect of prebiotics on measures of neurodevelopmental impairment (Bayley Scales of Infant Development (BSID) Mental Development Index score < 85: RR 0.84, 95% CI 0.25 to 2.90; very low-certainty evidence; BSID Psychomotor Development Index score < 85: RR 0.24, 95% 0.03 to 2.00; very low-certainty evidence; cerebral palsy: RR 0.35, 95% CI 0.01 to 8.35; very low-certainty evidence).

AUTHORS' CONCLUSIONS

The available trial data provide low-certainty evidence about the effects of prebiotics on the risk of NEC, all-cause mortality before discharge, and invasive infection, and very low-certainty evidence about the effect on neurodevelopmental impairment for very preterm or VLBW infants. Our confidence in the effect estimates is limited; the true effects may be substantially different. Large, high-quality trials are needed to provide evidence of sufficient validity to inform policy and practice decisions.

Development of the Neonatal Intestinal Barrier, Microbiome, and Susceptibility to NEC

The function of the intestinal barrier is partially dependent on host maturity and the colonization patterns of the microbiome to which it is exposed. Premature birth and stressors of neonatal intensive care unit (NICU)-related support (e.g., antibiotics, steroids, etc.) can alter the host internal environment resulting in changes in the intestinal barrier. Pathogenic microbial proliferation and breach of the immature intestinal barrier are proposed to be crucial steps in the development of neonatal diseases such as necrotizing enterocolitis. This article will review the current literature on the intestinal barrier in the neonatal gut, the consequences of microbiome development for this defense system, and how prematurity can influence neonatal susceptibility to gastrointestinal infection.

Probiotics to improve the gut microbiome in premature infants: are we there yet?

Gut microbiome maturation in infants born prematurely is uniquely influenced by the physiological, clinical, and environmental factors surrounding preterm birth and early life, leading to altered patterns of microbial succession relative to term infants during the first months of life. These differences in microbiome composition are implicated in acute clinical conditions that disproportionately affect preterm infants, including necrotizing enterocolitis (NEC) and late-onset sepsis (LOS). Probiotic supplementation initiated early in life is an effective prophylactic measure for preventing NEC, LOS, and other clinical concerns relevant to preterm infants. In parallel, reported benefits of probiotics on the preterm gut microbiome, metabolome, and immune function are beginning to emerge. This review summarizes the current literature on the influence of probiotics on the gut microbiome of preterm infants, outlines potential mechanisms by which these effects are exerted, and highlights important clinical considerations for determining the best practices for probiotic use in premature infants.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSION

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

Understanding the development and function of the gut microbiota in health and inflammation

The gut microbiota is known to play an important role in maintaining gut health through a symbiotic relationship with the host. Altered gut microbiota is a common feature of several diseases of the gastrointestinal tract; however, the causal relationship between microbiota and disease pathogenesis is poorly understood. Necrotising enterocolitis (NEC) and inflammatory bowel disease (IBD) are both severe inflammatory diseases affecting the gastrointestinal tract. Although they affect very different patient populations, with NEC primarily being a disease of prematurity and IBD predominantly affecting adults although children can be affected, they both demonstrate common features of gut microbial dysbiosis and a dysregulated host immune response. By comparing and contrasting the changes in gut microbiota, host immune response and function, we aim to highlight common features in diseases that may seem clinically unrelated. Key areas of interest are the role of pattern recognition receptors in altered recognition and responses to the gut microbiota by the host immune system and the associated dysfunctional gut epithelial barrier. The challenge of identifying causal relationships between microbiota and disease is ever-present; however, considering a disease-agnostic approach may help to identify mechanistic pathways shared across several clinical diseases.

Synbiotics to prevent necrotising enterocolitis in very preterm or very low birth weight infants

BACKGROUND

Intestinal dysbiosis may contribute to the pathogenesis of necrotising enterocolitis (NEC) in very preterm or very low birth weight (VLBW) infants. Dietary supplementation with synbiotics (probiotic micro-organisms combined with prebiotic oligosaccharides) to modulate the intestinal microbiome has been proposed as a strategy to reduce the risk of NEC and associated mortality and morbidity.

OBJECTIVES

To assess the effect of enteral supplementation with synbiotics (versus placebo or no treatment, or versus probiotics or prebiotics alone) for preventing NEC and associated morbidity and mortality in very preterm or VLBW infants.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials, MEDLINE, Embase, the Maternity and Infant Care database and CINAHL, from earliest records to 17 June 2021. We searched clinical trials databases and conference proceedings, and examined the reference lists of retrieved articles.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs comparing prophylactic synbiotics supplementation with placebo or no synbiotics in very preterm (< 32 weeks' gestation) or very low birth weight (< 1500 g) infants.

DATA COLLECTION AND ANALYSIS

Two review authors separately performed the screening and selection process,  evaluated risk of bias of the trials, extracted data, and synthesised effect estimates using risk ratio (RR), risk difference (RD), and mean difference, with associated 95% confidence intervals (CIs). We used the GRADE approach to assess the level of certainty for effects on NEC, all-cause mortality, late-onset invasive infection, and neurodevelopmental impairment.

MAIN RESULTS

We included six trials in which a total of 925 infants participated. Most trials were small (median sample size 200). Lack of clarity on methods used to conceal allocation and mask caregivers or investigators were potential sources of bias in four of the trials. The studied synbiotics preparations contained lactobacilli or bifidobacteria (or both) combined with fructo- or galacto-oligosaccharides (or both).  Meta-analyses suggested that synbiotics may reduce the risk of NEC (RR 0.18, 95% CI 0.09 to 0.40; RD 70 fewer per 1000, 95% CI 100 fewer to 40 fewer; number needed to treat for an additional beneficial outcome (NNTB) 14, 95% CI 10 to 25; six trials (907 infants); low certainty evidence); and all-cause mortality prior to hospital discharge (RR 0.53, 95% CI 0.33 to 0.85; RD 50 fewer per 1000, 95% CI 120 fewer to 100 fewer; NNTB 20, 95% CI 8 to 100; six trials (925 infants); low-certainty evidence). Synbiotics may have little or no effect on late-onset invasive infection, but the evidence is very uncertain (RR 0.84, 95% CI 0.58 to 1.21; RD 20 fewer per 1000, 95% CI 70 fewer to 30 more; five trials (707 infants); very low-certainty evidence). None of the trials assessed neurodevelopmental outcomes. In the absence of high levels of heterogeneity, we did not undertake any subgroup analysis (including the type of feeding).

AUTHORS' CONCLUSIONS

The available trial data provide only low-certainty evidence about the effects of synbiotics on the risk of NEC and associated morbidity and mortality for very preterm or very low birth weight infants. Our confidence in the effect estimates is limited; the true effects may be substantially different from these estimates. Large, high-quality trials would be needed to provide evidence of sufficient validity and applicability to inform policy and practice.

Use of Probiotics in Preterm Infants

Probiotic products in the United States are available for use in the general category of dietary supplements, bypassing the rigor of the US Food and Drug Administration (FDA) approval process in safety, efficacy, and manufacturing standards. As a result, currently available probiotics lack FDA-approved drug labeling and cannot be marketed to treat or prevent disease in preterm infants, including necrotizing enterocolitis and late-onset sepsis. Despite lack of availability of a pharmaceutical-grade product, the number of preterm infants receiving probiotics in the United States and Canada is steadily increasing. According to recent reports from large collaborative databases in the United States, approximately 10% of extremely low gestational age neonates receive a probiotic preparation during their stay in the NICU, with wide variation in practice among units. In sum, more than 10 000 preterm infants have been enrolled in randomized clinical trials of probiotic supplementation worldwide. Methodologic differences among study protocols included different strains and combinations of therapy, masking of trials, and a priori definitions of the primary outcome measure. Large meta-analyses of these trials have demonstrated the efficacy of multiple-strain probiotics in reducing necrotizing enterocolitis and all-cause mortality, whereas the efficacy of single-strain probiotic preparations is less certain. In the absence of an appropriate medical-grade product in the United States, dietary supplement-grade probiotics, some of which have been the subject of recent recalls for contamination, are being prescribed. Given the lack of FDA-regulated pharmaceutical-grade products in the United States, conflicting data on safety and efficacy, and potential for harm in a highly vulnerable population, current evidence does not support the routine, universal administration of probiotics to preterm infants, particularly those with a birth weight of <1000 g.

Synbiotics for preventing necrotising enterocolitis in preterm infants

This is a protocol for a Cochrane Review (intervention). The objectives are as follows:

To evaluate the effect of enteral supplementation with synbiotics (versus placebo or no treatment, or versus probiotics or prebiotics alone) on the risk of necrotising enterocolitis and associated morbidity and mortality in very preterm or very low birth weight infants.

Probiotics to prevent necrotising enterocolitis in very preterm or very low birth weight infants

BACKGROUND

Intestinal dysbiosis may contribute to the pathogenesis of necrotising enterocolitis (NEC) in very preterm or very low birth weight infants. Dietary supplementation with probiotics to modulate the intestinal microbiome has been proposed as a strategy to reduce the risk of NEC and associated mortality and morbidity.  OBJECTIVES: To determine the effect of supplemental probiotics on the risk of NEC and mortality and morbidity in very preterm or very low birth weight infants.

SEARCH METHODS

We searched Cochrane Central Register of Controlled Trials (CENTRAL; 2020, Issue 2) in the Cochrane Library; MEDLINE Ovid (1946 to 17 Feb 2020), Embase Ovid (1974 to 17 Feb 2020), Maternity & Infant Care Database Ovid (1971 to 17 Feb 2020), the Cumulative Index to Nursing and Allied Health Literature (1982 to 18 Feb 2020). We searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials (RCTs) and quasi-RCTs.

SELECTION CRITERIA

We included RCTs and quasi-RCTs comparing probiotic supplementation with placebo or no probiotics in very preterm or very low birth weight infants.

DATA COLLECTION AND ANALYSIS

We used the standard methods of Cochrane Neonatal. Two review authors separately evaluated trial quality, extracted data, and synthesised effect estimates using risk ratio (RR), risk difference (RD), and mean difference. We used the GRADE approach to assess the certainty of evidence for effects on NEC, all-cause mortality, late-onset infection, and severe neurodevelopmental impairment.

MAIN RESULTS

We included 56 trials in which 10,812 infants participated. Most trials were small (median sample size 149). Lack of clarity on methods to conceal allocation and mask caregivers or investigators were the main potential sources of bias in about half of the trials. Trials varied by the formulation of the probiotics. The most commonly used preparations contained Bifidobacterium spp., Lactobacillus spp., Saccharomyces spp., and Streptococcus spp. alone or in combinations. Meta-analysis showed that probiotics may reduce the risk of NEC: RR 0.54, 95% CI 0.45 to 0.65 (54 trials, 10,604 infants; I² = 17%); RD -0.03, 95% CI -0.04 to -0.02; number needed to treat for an additional beneficial outcome (NNTB) 33, 95% CI 25 to 50. Evidence was assessed as low certainty because of the limitations in trials design, and the presence of funnel plot asymmetry consistent with publication bias. Sensitivity meta-analysis of trials at low risk of bias showed a reduced risk of NEC: RR 0.70, 95% CI 0.55 to 0.89 (16 trials, 4597 infants; I² = 25%); RD -0.02, 95% CI -0.03 to -0.01; NNTB 50, 95% CI 33 to 100. Meta-analyses showed that probiotics probably reduce mortality (RR 0.76, 95% CI 0.65 to 0.89; (51 trials, 10,170 infants; I² = 0%); RD -0.02, 95% CI -0.02 to -0.01; NNTB 50, 95% CI 50 to 100), and late-onset invasive infection (RR 0.89, 95% CI 0.82 to 0.97; (47 trials, 9762 infants; I² = 19%); RD -0.02, 95% CI -0.03 to -0.01; NNTB 50, 95% CI 33 to 100). Evidence was assessed as moderate certainty for both these outcomes because of the limitations in trials design. Sensitivity meta-analyses of 16 trials (4597 infants) at low risk of bias did not show an effect on mortality or infection. Meta-analysis showed that probiotics may have little or no effect on severe neurodevelopmental impairment (RR 1.03, 95% CI 0.84 to 1.26 (five trials, 1518 infants; I² = 0%). The certainty on this evidence is low because of limitations in trials design and serious imprecision of effect estimate. Few data (from seven of the trials) were available for extremely preterm or extremely low birth weight infants. Meta-analyses did not show effects on NEC, death, or infection (low-certainty evidence).

AUTHORS' CONCLUSIONS

Given the low to moderate level of certainty about the effects of probiotic supplements on the risk of NEC and associated morbidity and mortality for very preterm or very low birth weight infants, and particularly for extremely preterm or extremely low birth weight infants, further, large, high-quality trials are needed to provide evidence of sufficient quality and applicability to inform policy and practice.

Does probiotic bacteremia in premature infants impact clinically relevant outcomes? A case report and updated review of literature

Prophylactic use of probiotics decreases the incidence of necrotizing enterocolitis (NEC) in premature infants. However, there are ongoing concerns related to the routine use of probiotics including inconsistent literature regarding optimal dose and strain, lack of regulatory standards in production and reports regarding potential side effects. There is limited data regarding the incidence of probiotic bacteremia and its impact on relevant clinical outcomes in the premature population. We report the first case of Bifidobacterium longum bacteremia in our center since the routine introduction of probiotics. The neonate had NEC with perforation on day of life 7, which likely led to translocation of the probiotic strain to the blood stream. The neonate did not have any hemodynamic instability and the repeat blood culture was negative after starting antibiotic therapy. We also conducted a literature review and found 13 other cases of probiotic bacteremia in premature or very low birth weight neonates. Although the incidence of probiotic bacteremia is low, it can impact several clinical outcomes including prolonged exposure to antibiotics, removal of central lines and additional laboratory testing such as lumbar puncture. There has been no mortality attributable to probiotic bacteremia and there is no data regarding long term neurodevelopmental outcomes.

Safety and efficacy of probiotic administration to preterm infants: ten common questions

In spite of a large number of randomized placebo-controlled clinical trials and observational cohort studies including >50,000 preterm infants from 29 countries that have demonstrated a decrease in the risk of necrotizing enterocolitis, death, and sepsis, routine prophylactic probiotic administration to preterm infants remains uncommon in much of the world. This manuscript reflects talks given at NEC Society Symposium in 2019 and is not intended to be a state-of-the-art review or systematic review, but a summary of the probiotic-specific aspects of the symposium with limited additions including a recent strain-specific network analysis and position statement from the European Society for Paediatric Gastroenterology Hepatology and Nutrition (ESPGHAN). We address ten common questions related to the intestinal microbiome and probiotic administration to the preterm infant.

Probiotics and Preterm Infants: A Position Paper by the European Society for Paediatric Gastroenterology Hepatology and Nutrition Committee on Nutrition and the European Society for Paediatric Gastroenterology Hepatology and Nutrition Working Group for Probiotics and Prebiotics

More than 10,000 preterm infants have participated in randomised controlled trials on probiotics worldwide, suggesting that probiotics in general could reduce rates of necrotising enterocolitis (NEC), sepsis, and mortality. Answers to relevant clinical questions as to which strain to use, at what dosage, and how long to supplement are, however, not available. On the other hand, an increasing number of commercial products containing probiotics are available from sometimes suboptimal quality. Also, a large number of units around the world are routinely offering probiotic supplementation as the standard of care despite lacking solid evidence. Our recent network meta-analysis identified probiotic strains with greatest efficacy regarding relevant clinical outcomes for preterm neonates. Efficacy in reducing mortality and morbidity was found for only a minority of the studied strains or combinations. In the present position paper, we aim to provide advice, which specific strains might potentially be used and which strains should not be used. In addition, we aim to address safety issues of probiotic supplementation to preterm infants, who have reduced immunological capacities and occasional indwelling catheters. For example, quality reassurance of the probiotic product is essential, probiotic strains should be devoid of transferable antibiotic resistance genes, and local microbiologists should be able to routinely detect probiotic sepsis. Provided all safety issues are met, there is currently a conditional recommendation (with low certainty of evidence) to provide either Lactobacillus rhamnosus GG ATCC53103 or the combination of Bifidobacterium infantis Bb-02, Bifidobacterium lactis Bb-12, and Streptococcus thermophilus TH-4 in order to reduce NEC rates.

Neonatal intestinal dysbiosis

The initial colonization of the neonatal intestinal tract is influenced by delivery mode, feeding, the maternal microbiota, and a host of environmental factors. After birth, the composition of the infant's microbiota undergoes a series of significant changes particularly in the first weeks and months of life ultimately developing into a more stable and diverse adult-like population in childhood. Intestinal dysbiosis is an alteration in the intestinal microbiota associated with disease and appears to be common in neonates. The consequences of intestinal dysbiosis are uncertain, but strong circumstantial evidence and limited confirmations of causality suggest that dysbiosis early in life can influence the health of the infant acutely, as well as contribute to disease susceptibility later in life.

Effects of artificially introduced Enterococcus faecalis strains in experimental necrotizing enterocolitis

Enterococcus faecalis is a ubiquitous intestinal symbiont and common early colonizer of the neonatal gut. Although colonization with E. faecalis has been previously associated with decreased pathology of necrotizing enterocolitis (NEC), these bacteria have been also implicated as opportunistic pathogens. Here we characterized 21 strains of E. faecalis, naturally occurring in 4-day-old rats, for potentially pathogenic properties and ability to colonize the neonatal gut. The strains differed in hemolysis, gelatin liquefaction, antibiotic resistance, biofilm formation, and ability to activate the pro-inflammatory transcription factor NF-κB in cultured enterocytes. Only 3 strains, BB70, 224, and BB24 appreciably colonized the neonatal intestine on day 4 after artificial introduction with the first feeding. The best colonizer, strain BB70, effectively displaced E. faecalis of maternal origin. Whereas BB70 and BB24 significantly increased NEC pathology, strain 224 significantly protected from NEC. Our results show that different strains of E. faecalis may be pathogenic or protective in experimental NEC.

Prophylactic use of probiotics for gastrointestinal disorders in children

The gastrointestinal microbiome is a hot topic in clinical research. Beneficial effects of selected probiotics in the prevention of gastrointestinal disorders are mainly restricted to acute gastroenteritis, antibiotic-associated diarrhoea, infantile colic, and necrotising enterocolitis. However, no broad consensus exists to recommend the use of probiotics in the prevention of these conditions, mainly because of the different design of the studies done so far, resulting in little evidence for specific strains, dosages, and indications. More well designed studies are needed before recommendations can be proposed. At this stage, the evidence is insufficient to recommend the routine use of probiotics in infants and children for the prevention of gastrointestinal disorders.

Dysbiosis and Prematurity: Is There a Role for Probiotics?

Healthy microbiota is a critical mediator in maintaining health and it is supposed that dysbiosis could have a role in the pathogenesis of a number of diseases. Evidence supports the hypothesis that maternal dysbiosis could act as a trigger for preterm birth; aberrant colonization of preterm infant gut might have a role in feeding intolerance and pathogenesis of necrotizing enterocolitis. Despite several clinical trials and meta-analyses, it is still not clear if modulation of maternal and neonatal microbiota with probiotic supplementation decreases the risk of preterm birth and its complications.

Immunonutrition for Preterm Infants

Care and outcomes for very preterm infants continue to improve, but important causes of mortality and acute and long-term morbidity associated with prolonged hospitalisation remain. Necrotising enterocolitis (NEC) and late-onset infection have emerged as the major causes of death beyond the early neonatal period and of neurodisability in very preterm infants. Although the pathogenesis of these conditions is incompletely understood, it appears to be related to the content and mode of delivery of the enteral diet, particularly the impact of immunonutrients from human breast milk on the microbial and metabolic balance within the immature intestine. Evidence exists to support investment in measures to help mothers to express breast milk as the primary source of nutrition for their very preterm infants. In the absence of maternal milk, pasteurised donor breast milk provides protection against NEC, but its nutritive adequacy is not clear and its cost-effectiveness is uncertain. Supplementation with individual immunonutrients, including immunoglobulins and lactoferrin, has not been shown to be effective in preventing NEC or infection in randomised controlled trials. The evidence base for prebiotics and probiotics is stronger, but concerns exist about the choice, safety and availability of formulations. Other strategies - including avoidance of drugs such as gastric acid suppressants that compromise innate immunity, as well as evidence-based progressive feeding strategies that reduce exposure to invasive interventions - are emerging as key components of care packages to reduce the burden of NEC, infection and associated growth and developmental faltering for very preterm infants.