B. infantis EVC001 Is Well-Tolerated and Improves Human Milk Oligosaccharide Utilization in Preterm Infants in the Neonatal Intensive Care Unit

Effect of probiotic supplementation on the gut microbiota in very preterm infants: a systematic review

OBJECTIVE

There is increasing evidence that probiotic supplementation in very preterm infants decreases the risk of necrotising enterocolitis (NEC), sepsis and mortality. The underlying mechanisms, including effects on the gut microbiota, are largely unknown. We aimed to systematically review the available literature on the effects of probiotic supplementation in very preterm infants on gut microbiota development.

DESIGN

A systematic review in Medline, Embase, Cochrane Library, CINAHL and Web of Science.

SETTING

Neonatal intensive care unit.

PATIENTS

Premature infants.

INTERVENTION

Probiotic supplementation.

MAIN OUTCOME MEASURES

Gut microbiota.

RESULTS

A total of 1046 articles were screened, of which 29 were included. There was a large heterogeneity in study design, dose and type of probiotic strains, timepoints of sample collection and analysing techniques. Bifidobacteria and lactobacilli were the most used probiotic strains. The effects of probiotics on alpha diversity were conflicting; however, beta diversity was significantly different between probiotic-supplemented infants and controls in the vast majority of studies. In most studies, probiotic supplementation led to increased relative abundance of the supplemented strains and decreased abundance of genera such as Clostridium, Streptococcus, Klebsiella and Escherichia.

CONCLUSIONS

Probiotic supplementation to preterm infants seems to increase the relative abundance of the supplemented strains with a concurrent decrease of potentially pathogenic species. These probiotic-induced microbial alterations may contribute to the decreased risk of health complications such as NEC. Future trials, including omics technologies to analyse both microbiota composition and function linked to health outcomes, are warranted to identify the optimal mixture and dosing of probiotic strains.

PROSPERO REGISTRATION NUMBER

CRD42023385204.

Efficacy and Safety of Bifidobacterium longum Supplementation in Infants: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Strategies to stabilize and support overall infant health by increasing the number of Bifidobacterium longum in the infant gut are of interest, but few studies have systematically addressed this issue. We aimed to evaluate the efficacy and safety of Bifidobacterium longum use in infants using meta-analysis.

METHODS

We searched PubMed, EMBASE, Cochrane Library of Systematic Reviews, and SinoMed for publications until 27 July 2022. The main outcomes of interest were weight gain, risk of necrotizing enterocolitis (NEC), and adverse events. Two authors independently performed study screening, risk of bias assessment, and data extraction. Outcome data were extracted from each included study and combined using mean difference (MD) or risk ratio (RR) and finally combined using a fixed-effect model or random-effect model.

RESULTS

A total of 4481 relevant studies were identified, of which 15 were found to be eligible for randomized controlled trials and were included in the meta-analysis. The combined extracted data showed that the intervention group containing Bifidobacterium longum had a significantly lower risk of NEC (RR = 0.539, 95% CI: 0.333, 0.874) compared to the control group. There was no statistical difference between the intervention and control groups regarding weight gain (MD = 0.029, 95% CI: -0.032, 0.090), the occurrence of adverse events (RR = 0.986, 95% CI: 0.843, 1.153), and serious adverse events (RR = 0.881, 95% CI: 0.493, 1.573).

CONCLUSIONS

Bifidobacterium longum may significantly reduce the risk of NEC in infants as well as being safe; thus, further research evidence is needed on whether there is a benefit on weight gain.

Early Probiotic Supplementation of Healthy Term Infants with Bifidobacterium longum subsp. infantis M-63 Is Safe and Leads to the Development of Bifidobacterium-Predominant Gut Microbiota: A Double-Blind, Placebo-Controlled Trial

Bifidobacteria are important intestinal bacteria that provide a variety of health benefits in infants. We investigated the efficacy and safety of Bifidobacterium longum subsp. infantis (B. infantis) M-63 in healthy infants in a double-blind, randomized, placebo-controlled trial. Healthy term infants were given B. infantis M-63 (n = 56; 1 × 109 CFU/day) or placebo (n = 54) from postnatal age ≤ 7 days to 3 months. Fecal samples were collected, and fecal microbiota, stool pH, short-chain fatty acids, and immune substances were analyzed. Supplementation with B. infantis M-63 significantly increased the relative abundance of Bifidobacterium compared with the placebo group, with a positive correlation with the frequency of breastfeeding. Supplementation with B. infantis M-63 led to decreased stool pH and increased levels of acetic acid and IgA in the stool at 1 month of age compared with the placebo group. There was a decreased frequency of defecation and watery stools in the probiotic group. No adverse events related to test foods were observed. These results indicate that early supplementation with B. infantis M-63 is well tolerated and contributes to the development of Bifidobacterium-predominant gut microbiota during a critical developmental phase in term infants.

Biotics in neonatal period: what's the evidence?

Breastfeeding is considered the gold standard for infants' nutrition and provides unique benefits for infants' health. Great research interest has been raised about the use of bioactive components in neonatal medicine, both as standalone products and as addition to infant formula, in the attempt to reproduce human milk beneficial effects. Thus, the aim of this narrative review is to summarize most recent evidence on biotics' use in the neonatal period, with a focus on infant formula (IF) supplemented with probiotics, prebiotics, synbiotics and postbiotics. Growing data indicate overall positive effects of biotic supplemented formula on microbiome composition and metabolic activity. Furthermore, some benefits are also emerging from randomized controlled trials evaluating the clinical impact these enriched formulas may have on the health of formula fed infants. However, clear evidence still lacks and none of this supplemented IF has demonstrated conclusive superiority. To date, whereas no routine recommendations can be done, biotics supplemented IF have generally proven to be well-tolerated and safe in ensuring infants' normal growth, paving the way for future IF alternatives for those infants who are not able to be (fully) breastfed. More RCTs, with adequate design and statistical power, are still needed to better clarify, if present, which benefits the supplementation of IF may confer to infants' short and long-term outcomes.

Human Milk Oligosaccharide Utilization in Intestinal Bifidobacteria Is Governed by Global Transcriptional Regulator NagR

Bifidobacterium longum subsp. infantis is a prevalent beneficial bacterium that colonizes the human neonatal gut and is uniquely adapted to efficiently use human milk oligosaccharides (HMOs) as a carbon and energy source. Multiple studies have focused on characterizing the elements of HMO utilization machinery in B. longum subsp. infantis; however, the regulatory mechanisms governing the expression of these catabolic pathways remain poorly understood. A bioinformatic regulon reconstruction approach used in this study implicated NagR, a transcription factor from the ROK family, as a negative global regulator of gene clusters encoding lacto-N-biose/galacto-N-biose (LNB/GNB), lacto-N-tetraose (LNT), and lacto-N-neotetraose (LNnT) utilization pathways in B. longum subsp. infantis. This conjecture was corroborated by transcriptome profiling upon nagR genetic inactivation and experimental assessment of binding of recombinant NagR to predicted DNA operators. The latter approach also implicated N-acetylglucosamine (GlcNAc), a universal intermediate of LNT and LNnT catabolism, and its phosphorylated derivatives as plausible NagR transcriptional effectors. Reconstruction of NagR regulons in various Bifidobacterium lineages revealed multiple potential regulon expansion events, suggesting evolution from a local regulator of GlcNAc catabolism in ancestral bifidobacteria to a global regulator controlling the utilization of mixtures of GlcNAc-containing host glycans in B. longum subsp. infantis and Bifidobacterium bifidum. IMPORTANCE The predominance of bifidobacteria in the gut of breastfed infants is attributed to the ability of these bacteria to metabolize human milk oligosaccharides (HMOs). Thus, individual HMOs such as lacto-N-tetraose (LNT) and lacto-N-neotetraose (LNnT) are considered promising prebiotics that would stimulate the growth of bifidobacteria and confer multiple health benefits to preterm and malnourished children suffering from impaired (stunted) gut microbiota development. However, the rational selection of HMO-based prebiotics is hampered by the incomplete knowledge of regulatory mechanisms governing HMO utilization in target bifidobacteria. This study describes NagR-mediated transcriptional regulation of LNT and LNnT utilization in Bifidobacterium longum subsp. infantis. The elucidated regulatory network appears optimally adapted to simultaneous utilization of multiple HMOs, providing a rationale to add HMO mixtures (rather than individual components) to infant formulas. The study also provides insights into the evolutionary trajectories of complex regulatory networks controlling carbohydrate metabolism in bifidobacteria.

Milk glycan metabolism by intestinal bifidobacteria: insights from comparative genomics

Bifidobacteria are early colonizers of the human neonatal gut and provide multiple health benefits to the infant, including inhibiting the growth of enteropathogens and modulating the immune system. Certain Bifidobacterium species prevail in the gut of breastfed infants due to the ability of these microorganisms to selectively forage glycans present in human milk, specifically human milk oligosaccharides (HMOs) and N-linked glycans. Therefore, these carbohydrates serve as promising prebiotic dietary supplements to stimulate the growth of bifidobacteria in the guts of children suffering from impaired gut microbiota development. However, the rational formulation of milk glycan-based prebiotics requires a detailed understanding of how bifidobacteria metabolize these carbohydrates. Accumulating biochemical and genomic data suggest that HMO and N-glycan assimilation abilities vary remarkably within the Bifidobacterium genus, both at the species and strain levels. This review focuses on the delineation and genome-based comparative analysis of differences in respective biochemical pathways, transport systems, and associated transcriptional regulatory networks, providing a foundation for genomics-based projection of milk glycan utilization capabilities across a rapidly growing number of sequenced bifidobacterial genomes and metagenomic datasets. This analysis also highlights remaining knowledge gaps and suggests directions for future studies to optimize the formulation of milk-glycan-based prebiotics that target bifidobacteria.