Effects of Probiotics on Gut Microbiomes of Extremely Preterm Infants in the Neonatal Intensive Care Unit: A Prospective Cohort Study

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.

Safety and Effectiveness of Probiotics in Preterm Infants with Necrotizing Enterocolitis

Although necrotizing enterocolitis is a leading cause of morbidity and mortality among preterm infants, its underlying pathophysiology is not fully understood. Gut dysbiosis, an imbalance between commensal and pathogenic microbes, in the preterm infant is likely a major contributor to the development of necrotizing enterocolitis. In this review, we will discuss the increasing use of probiotics in the NICU, an intervention aimed to mitigate alterations in the gut microbiome. We will review the existing evidence regarding the safety and effectiveness of probiotics, and their potential to reduce rates of necrotizing enterocolitis in preterm infants.

Safety and Effectiveness of Probiotics in Preterm Infants with Necrotizing Enterocolitis

Although necrotizing enterocolitis is a leading cause of morbidity and mortality among preterm infants, its underlying pathophysiology is not fully understood. Gut dysbiosis, an imbalance between commensal and pathogenic microbes, in the preterm infant is likely a major contributor to the development of necrotizing enterocolitis. In this review, we will discuss the increasing use of probiotics in the NICU, an intervention aimed to mitigate alterations in the gut microbiome. We will review the existing evidence regarding the safety and effectiveness of probiotics, and their potential to reduce rates of necrotizing enterocolitis in preterm infants.

More than nutrition: Therapeutic potential and mechanism of human milk oligosaccharides against necrotizing enterocolitis

Human milk is the most valuable source of nutrition for infants. The structure and function of human milk oligosaccharides (HMOs), which are key components of human milk, have long been attracting particular research interest. Several recent studies have found HMOs to be efficacious in the prevention and treatment of necrotizing enterocolitis (NEC). Additionally, they could be developed in the future as non-invasive predictive markers for NEC. Based on previous findings and the well-defined functions of HMOs, we summarize potential protective mechanisms of HMOs against neonatal NEC, which include: modulating signal receptor function, promoting intestinal epithelial cell proliferation, reducing apoptosis, restoring intestinal blood perfusion, regulating microbial prosperity, and alleviating intestinal inflammation. HMOs supplementation has been demonstrated to be protective against NEC in both animal studies and clinical observations. This calls for mass production and use of HMOs in infant formula, necessitating more research into the safety of industrially produced HMOs and the appropriate dosage in infant formula.

Probiotic supplementation modifies the gut microbiota profile of very low birth weight preterm infants during hospitalization

BACKGROUND

Probiotic supplementation is increasingly being given to very low birth weight (VLBW) preterm infants. This preliminary observational study aimed to investigate the effects of multiple-strain probiotics on the gut microbiota of VLBW preterm infants.

METHODS

We collected meconium and stool samples on days 14, 30, and 60 after birth from 49 VLBW infants with a gestational age of <32 weeks. The infants were divided into the probiotics (n = 24) and control (n = 25) groups. The microbial composition and diversity in the gut of the two groups were analyzed using 16 S rRNA gene sequencing.

RESULTS

The relative abundance of Bifidobacterium and Lactobacillus was significantly higher in the probiotics group than in the control group on days 14, 30, and 60 (Bifidobacterium: p = 0.002, p < 0.0001, and p < 0.0001, respectively; Lactobacillus: p = 0.012, p < 0.0001, and p < 0.0001, respectively). The control group exhibited a significantly higher proportion of participants with a low abundance (<1%) of Bifidobacterium or Lactobacillus on days 14, 30, and 60 than those in the probiotic group. Moreover, the probiotics group exhibited a significantly lower abundance of Klebsiella on days 14 and 30 (2.4% vs. 11.6%, p = 0.037; and 7.9% vs. 16.6%, p = 0.032, respectively) and of Escherichia-Shigella on day 60 than the control group (6.1% vs. 12.3%, p = 0.013). Beta diversity analysis revealed that the microbiota profile was clearly divided into two groups on days 30 and 60 (p = 0.001).

CONCLUSION

Probiotic supplementation significantly increased the relative abundance of Bifidobacterium and Lactobacillus and inhibited the growth of potential pathogens. Furthermore, probiotic supplementation led to a distinct gut microbiota profile. Further research is needed to identify probiotic strains that exert significant influence on the gut microbiome and their long-term health implications in preterm infants.

Scarring the early-life microbiome: its potential life-long effects on human health and diseases

The gut microbiome is widely recognized as a dynamic organ with a profound influence on human physiology and pathology. Extensive epidemiological and longitudinal cohort studies have provided compelling evidence that disruptions in the early-life microbiome can have long-lasting health implications. Various factors before, during, and after birth contribute to shaping the composition and function of the neonatal and infant microbiome. While these alterations can be partially restored over time, metabolic phenotypes may persist, necessitating research to identify the critical period for early intervention to achieve phenotypic recovery beyond microbiome composition. In this review, we provide current understanding of changes in the gut microbiota throughout life and the various factors affecting these changes. Specifically, we highlight the profound impact of early-life gut microbiota disruption on the development of diseases later in life and discuss perspectives on efforts to recover from such disruptions. [BMB Reports 2023; 56(9): 469-481].

Therapeutic Potential of Gut Microbiota and Its Metabolite Short-Chain Fatty Acids in Neonatal Necrotizing Enterocolitis

Short chain fatty acids (SCFAs), the principle end-products produced by the anaerobic gut microbial fermentation of complex carbohydrates (CHO) in the colon perform beneficial roles in metabolic health. Butyrate, acetate and propionate are the main SCFA metabolites, which maintain gut homeostasis and host immune responses, enhance gut barrier integrity and reduce gut inflammation via a range of epigenetic modifications in DNA/histone methylation underlying these effects. The infant gut microbiota composition is characterized by higher abundances of SCFA-producing bacteria. A large number of in vitro/vivo studies have demonstrated the therapeutic implications of SCFA-producing bacteria in infant inflammatory diseases, such as obesity and asthma, but the application of gut microbiota and its metabolite SCFAs to necrotizing enterocolitis (NEC), an acute inflammatory necrosis of the distal small intestine/colon affecting premature newborns, is scarce. Indeed, the beneficial health effects attributed to SCFAs and SCFA-producing bacteria in neonatal NEC are still to be understood. Thus, this literature review aims to summarize the available evidence on the therapeutic potential of gut microbiota and its metabolite SCFAs in neonatal NEC using the PubMed/MEDLINE database.

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.

Emerging issues in probiotic safety: 2023 perspectives

Probiotics are used for both generally healthy consumers and in clinical settings. However, theoretical and proven adverse events from probiotic consumption exist. New probiotic strains and products, as well as expanding use of probiotics into vulnerable populations, warrants concise, and actionable recommendations on how to work toward their safe and effective use. The International Scientific Association for Probiotics and Prebiotics convened a meeting to discuss and produce evidence-based recommendations on potential acute and long-term risks, risks to vulnerable populations, the importance for probiotic product quality to match the needs of vulnerable populations, and the need for adverse event reporting related to probiotic use. The importance of whole genome sequencing, which enables determination of virulence, toxin, and antibiotic resistance genes, as well as clear assignment of species and strain identity, is emphasized. We present recommendations to guide the scientific and medical community on judging probiotic safety.

Age disparities in intestinal stem cell quantities: a possible explanation for preterm infant susceptibility to necrotizing enterocolitis

PURPOSE

Preterm infants are more susceptible to necrotizing enterocolitis (NEC) than term Queryinfants. This may be due to a relative paucity of Lgr5⁺ or Bmi1⁺-expressing intestinal stem cells (ISCs) which are responsible for promoting intestinal recovery after injury. We hypothesized that the cellular markers of Lgr5⁺ and Bmi1⁺, which represent the two distinct ISC populations, would be lower in younger mice compared to older mice. In addition, we hypothesized that experimental NEC would result in a greater loss of Lgr5⁺ expression compared to Bmi1⁺ expression.

METHODS

Transgenic mice with EGFP-labeled Lgr5 underwent euthanasia at 10 different time points from E15 to P56 (n = 8-11/group). Lgr5⁺-expressing ISCs were quantified by GFP ELISA and Bmi1⁺ was assessed by qPCR. In addition, Lgr5^EGFP mice underwent experimental NEC via formula feeding and hypoxic and hypothermic stress. Additional portions of the intestine underwent immunostaining with anti-GFP or anti-Bmi1⁺ antibodies to confirm ELISA and PCR results. For statistical analysis, p < 0.05 was significant.

RESULTS

Lgr5⁺ and Bmi1⁺expression was lowest in embryonal and early postnatal mice and increased with age in all segments of the intestine. Experimental NEC was associated with loss of Lgr5⁺-expressing ISCs but no significant change in Bmi1⁺ expression.

CONCLUSION

Lgr5⁺ and Bmi1⁺ expression increase with age. Lgr5⁺-expressing ISCs are lower following experimental necrotizing enterocolitis while Bmi1⁺ expression remains relatively unchanged. Developing a targeted medical therapy to protect the low population of ISCs in preterm infants may promote tissue recovery and regeneration after injury from NEC.