LOS in The Dysbiotic Gut

Probiotic effect in preterm neonates with sepsis - A systematic review protocol

Background: The microbiota in the intestine is made up of trillions of living bacteria that coexist with the host. Administration of antibiotics during neonatal infection causes depletion of gut flora resulting in gut dysbiosis. Over the last few decades, probiotics have been created and promoted as microbiota management agents to enrich gut flora. Probiotics decrease the overgrowth of pathogenic bacteria in the gut of preterm neonates, reducing the frequency of nosocomial infections in the Neonatal Intensive Care Unit (NICUs). Methods: The systematic review will include randomized control trials (RCTs) of premier neonates with sepsis. Studies will be retrieved from global databases like Cochrane CENTRAL, CINAHL Plus via EBSCO host, MEDLINE via PubMed, EMBASE, SCOPUS, Ovid, Web of Science, ProQuest Medical Library, Microsoft academic, and DOAJ by utilizing database-specific keywords. Screening, data extraction, and critical appraisal of included research will be carried out separately by two review writers. Findings will be reported in accordance with the PRISMS-P 2020 guidelines. Conclusions: The findings of this systematic review will help to translate the evidence-based information needed to encourage the implementation of potential research output in the field of neonatal intensive care, guide best clinical practise, assist policy making and implementation to prevent gut dysbiosis in neonates with sepsis by summarising and communicating the evidence on the topic. PROSPERO registration number: This systematic review protocol has been registered in PROSPERO (Prospective Register of Systematic Reviews) on 10 th March 2022. The registration number is CRD42022315980.

Maternal melatonin supplementation shapes gut microbiota and protects against inflammation in early life

BACKGROUND

Gut microbiota colonization is critical for immune education and nutrient metabolism. Research shows that melatonin has beneficial effects as a therapy for many diseases via modulating gut dysbiosis. However, it is unclear whether melatonin alters gut microbiota colonization in early life.

METHODS

In the experimental group (Mel), mice were intraperitoneally injected with melatonin at 10 mg/kg body weight for embryonic days 14-16 and received drinking water containing 0.4 mg/mL melatonin until 28 days postpartum. In the control group (Ctrl), mice were injected with the same volume of 2.5% ethanol in saline and provided with standard water. Two more groups were created by treating neonatal mice with 20 mg/kg lipopolysaccharide (LPS) to induce inflammation, resulting in the groups Ctrl + LPS and Mel + LPS, respectively. We examined the gut microbiota of the neonatal mice in the Ctrl and Mel group on Days 7, 14, 21, and 28 post-birth. On Day 14, melatonin and short-chain fatty acids (SCFAs) concentrations were measured in the Ctrl and Mel group and the mice were treated with LPS to be evaluated for intestinal injury and inflammatory response 15 h post treatment. According to the result of the SCFAs concentrations, some neonatal mice were intraperitoneally injected with 500 mg/kg sodium butyrate (SB) from Days 11-13, intraperitoneally injected with 20 mg/kg LPS on Day 14, and then euthanized by carbon dioxide inhalation the next morning. Intestinal injury and inflammatory responses were evaluated in the Ctrl + LPS and SB + LPS groups, respectively.

RESULTS

By Day 14, it was evident that maternal melatonin supplementation significantly increased the relative abundance of Firmicutes in the ileal [61.03 (35.35 - 76.18) % vs. 98.02 (86.61 - 99.01) %, P = 0.003] and colonic [73.88 (69.77 - 85.99) % vs. 96.16 (94.57 - 96.34) %, P = 0.04] microbiota, the concentration of melatonin (0.79 ± 0.49 ng/ml vs. 6.11 ± 3.48 ng/ml, P = 0.008) in the gut lumen, and the fecal butyric acid (12.91 ± 5.74 μg/g vs. 23.58 ± 10.71 μg/g, P = 0.026) concentration of neonatal mice. Melatonin supplementation, and sodium butyrate treatment markedly alleviated intestinal injury and decreased inflammatory factors in neonatal mice.

CONCLUSION

This study suggests that maternal melatonin supplementation can shape the gut microbiota and metabolism of offspring under normal physiological conditions and protect them against LPS-induced inflammation in early life.

Maternal anthropometric variables and clinical factors shape neonatal microbiome

Recent studies indicate the existence of a complex microbiome in the meconium of newborns that plays a key role in regulating many host health-related conditions. However, a high variability between studies has been observed so far. In the present study, the meconium microbiome composition and the predicted microbial metabolic pathways were analysed in a consecutive cohort of 96 full-term newborns. The effect of maternal epidemiological variables on meconium diversity was analysed using regression analysis and PERMANOVA. Meconium microbiome composition mainly included Proteobacteria (30.95%), Bacteroidetes (23.17%) and Firmicutes (17.13%), while for predicted metabolic pathways, the most abundant genes belonged to the class “metabolism”. We observed a significant effect of maternal Rh factor on Shannon and Inverse Simpson indexes (p = 0.045 and p = 0.049 respectively) and a significant effect of delivery mode and maternal antibiotic exposure on Jaccard and Bray–Curtis dissimilarities (p = 0.001 and 0.002 respectively), while gestational age was associated with observed richness and Shannon indexes (p = 0.018 and 0.037 respectively), and Jaccard and Bray–Curtis dissimilarities (p = 0.014 and 0.013 respectively). The association involving maternal Rh phenotype suggests a role for host genetics in shaping meconium microbiome prior to the exposition to the most well-known environmental variables, which will influence microbiome maturation in the newborn.

The Microbiota-Gut Axis in Premature Infants: Physio-Pathological Implications

Intriguing evidence is emerging in regard to the influence of gut microbiota composition and function on host health from the very early stages of life. The development of the saprophytic microflora is conditioned by several factors in infants, and peculiarities have been found for babies born prematurely. This population is particularly exposed to a high risk of infection, postnatal antibiotic treatment, feeding difficulties and neurodevelopmental disabilities. To date, there is still a wide gap in understanding all the determinants and the mechanism behind microbiota disruption and its influence in the development of the most common complications of premature infants. A large body of evidence has emerged during the last decades showing the existence of a bidirectional communication axis involving the gut microbiota, the gut and the brain, defined as the microbiota–gut–brain axis. In this context, given that very few data are available to demonstrate the correlation between microbiota dysbiosis and neurodevelopmental disorders in preterm infants, increasing interest has arisen to better understand the impact of the microbiota–gut–brain axis on the clinical outcomes of premature infants and to clarify how this may lead to alternative preventive, diagnostic and therapeutic strategies. In this review, we explored the current evidence regarding microbiota development in premature infants, focusing on the effects of delivery mode, type of feeding, environmental factors and possible influence of the microbiota–gut–brain axis on preterm clinical outcomes during their hospital stay and on their health status later in life.

Subclinical necrotizing enterocolitis-induced systemic immune suppression in neonatal preterm pigs

Preterm infants are at high risks of sepsis and necrotizing enterocolitis (NEC). Some develop sepsis shortly after suspected or confirmed NEC, implying that NEC may predispose to sepsis but the underlying mechanisms are unknown. Using NEC-sensitive preterm pigs as models, we investigated the immune status in animals following development of subclinical NEC-like lesions with variable severities. Caesarean-delivered preterm pigs were reared until day 5 or day 9. Blood was analyzed for T-cell subsets, neutrophil phagocytosis, transcriptomics, and immune responses to in vitro LPS challenge. Gut tissues were used for histology and cytokine analyses. Pigs with/without macroscopic NEC lesions were scored as healthy, mild, or severe NEC. Overall NEC incidence was similar on day 5 and day 9 (61%-62%) but with lower severity on day 9, implying gradual mucosal repair following the early phase of NEC. Pigs with NEC showed decreased goblet cell density and increased MPO⁺ and CD3⁺ cell infiltration in the distal small intestine or colon. Mild or severe NEC lesions had limited effects on circulating parameters on day 5. On day 9, pigs with NEC lesions (especially severe lesions) showed systemic immune suppression, as indicated by elevated Treg frequency, impaired neutrophil phagocytosis, low expression of genes related to innate immunity and Th1 polarization, and diminished LPS-induced immune responses. In conclusion, we shows evidence for NEC-induced systemic immune suppression, even with mild and subclinical NEC lesions. The results help to explain that preterm infants suffering from NEC may show high sensitivity to later secondary infections and sepsis.NEW & NOTEWORTHY Necrotizing enterocolitis (NEC) and sepsis are common diseases in preterm infants. Many develop sepsis following an episode of suspected NEC, suggesting NEC as a predisposing factor for sepsis but mechanisms are unclear. Using preterm pigs as a model, now we show that subclinical NEC lesions, independent of clinical confounding factors, induces systemic immune suppression. The results may help to explain the increased risks of infection and sepsis in preterm infants with previous NEC diagnosis.

Exploring the Role of Gut Bacteria in Health and Disease in Preterm Neonates

The mortality rate of very preterm infants with birth weight <1500 g is as high as 15%. The survivors till discharge have a high incidence of significant morbidity, which includes necrotising enterocolitis (NEC), early-onset neonatal sepsis (EONS) and late-onset neonatal sepsis (LONS). More than 25% of preterm births are associated with microbial invasion of amniotic cavity. The preterm gut microbiome subsequently undergoes an early disruption before achieving bacterial maturation. It is postulated that bacterial gut colonisation at birth and postnatal intestinal dysbacteriosis precede the development of NEC and LONS in very preterm infants. In fact, bacterial colonization patterns in preterm infants greatly differ from term infants due to maternal chorioamnionitis, gestational age, delivery method, feeding type, antibiotic exposure and the environment factor in neonatal intensive care unit (NICU). In this regard, this review provides an overview on the gut bacteria in preterm neonates' meconium and stool. More than 50% of preterm meconium contains bacteria and the proportion increases with lower gestational age. Researchers revealed that the gut bacterial diversity is reduced in preterm infants at risk for LONS and NEC. Nevertheless, the association between gut dysbacteriosis and NEC is inconclusive with regards to relative bacteria abundance and between-sample beta diversity indices. With most studies show a disruption of the Proteobacteria and Firmicutes preceding the NEC. Hence, this review sheds light on whether gut bacteria at birth either alone or in combination with postnatal gut dysbacteriosis are associated with mortality and the morbidity of LONS and NEC in very preterm infants.

Understanding the Elements of Maternal Protection from Systemic Bacterial Infections during Early Life

Late-onset sepsis (LOS) and other systemic bloodstream infections are notable causes of neonatal mortality, particularly in prematurely born very low birth weight infants. Breastfeeding in early life has numerous health benefits, impacting the health of the newborn in both the short-term and in the long-term. Though the known benefits of an exclusive mother's own milk diet in early life have been well recognized and described, it is less understood how breastfed infants enjoy a potential reduction in risk of LOS and other systemic infections. Here we review how gut residing pathogens within the intestinal microbiota of infants can cause a subset of sepsis cases and the components of breastmilk that may prevent the dissemination of pathogens from the intestine.