Conditioned medium from Bifidobacteria infantis protects against Cronobacter sakazakii-induced intestinal inflammation in newborn mice

Unlocking the power of probiotics, postbiotics: targeting apoptosis for the treatment and prevention of digestive diseases

Digestive diseases are becoming an increasingly serious health burden, creating an urgent need to develop more effective treatment strategies. Probiotics and postbiotics have been extensively studied for their potential to prevent and treat digestive diseases. Growing evidence suggests that programmed cell death, especially apoptosis, is a critical mechanism influencing the molecular and biological aspects of digestive diseases, contributing to disease progression. Understanding the mechanisms and signaling pathways by which probiotics and postbiotics regulate apoptosis could reveal new therapeutic targets for treating digestive diseases. This review focuses on the beneficial effects of probiotics and postbiotics in regulating apoptosis across a range of liver diseases, including non-alcoholic fatty liver disease, liver injury, cirrhosis, and liver cancer. It also explores their effects on gastrointestinal diseases, such as colorectal cancer, colitis, gastrointestinal injury, and infectious diarrhea. Furthermore, some probiotics help balance the gut microbiota, enhance intestinal barrier function, and regulate the immune system, all of which are closely associated with apoptosis. Moreover, emerging technologies, such as encapsulation methods, have been developed to stabilize probiotics, primarily based on experimental findings from rodent and human studies.

Probiotic Saccharomyces boulardii Against Cronobacter sakazakii Infection: In Vitro and In Vivo Studies

Cronobacter sakazakii is an opportunistic foodborne pathogen causing intestinal and extra-intestinal diseases in humans, especially young children, and is regarded as one of the main concerns in public health. Saccharomyces boulardii is a well-known probiotic yeast widely used to treat and prevent antibiotic-associated diarrheal infections in infants and neonates. This study evaluated the preventive effects and potential of probiotic S. boulardii against C. sakazakii intestinal infections in humans. Viability, bacterial virulence factor, cellular pro-inflammatory gene expression, and nanomechanical properties of the cytoplasmic membrane of caco-2 cells were evaluated using MTT, real-time PCR, and AFM methods, respectively. Using histopathological analysis, S. boulardii treatment was evaluated on infected newborn C57 BL/6 mice. We found that S. boulardii inoculation significantly (P < 0.05) increased the viability and downregulated the cellular pro-inflammatory genes (IL-8 and NFkB) and bacterial virulence factor genes (ompA and hfq) in infected intestinal cells while also decreasing the morphological alterations. We also observed that S. boulardii treatment reduced the intestinal damage induced by C. sakazakii infection. In conclusion, our findings demonstrate that S. boulardii effectively protects against C. sakazakii infections. This probiotic yeast holds promise as a potential preventive and therapeutic agent for intestinal diseases associated with C. sakazakii.

PhoP/PhoQ Two-Component System Contributes to Intestinal Inflammation Induced by Cronobacter sakazakii in Neonatal Mice

Cronobacter sakazakii (C. sakazakii) is a foodborne pathogen capable of causing severe infections in newborns. The PhoP/PhoQ two-component system exerts a significant influence on bacterial virulence. This study aimed to investigate the impact of the PhoP/PhoQ system on intestinal inflammation in neonatal mice induced by C. sakazakii. Neonatal mice were infected orally by C. sakazakii BAA-894 (WT), a phoPQ-gene-deletion strain (ΔphoPQ), and a complementation strain (ΔphoPQC), and the intestinal inflammation in the mice was monitored. Deletion of the phoPQ gene reduced the viable count of C. sakazakii in the ileum and alleviated intestinal tissue damage. Moreover, caspase-3 activity in the ileum of the WT- and ΔphoPQC-infected mice was significantly elevated compared to that of the ΔphoPQ and control groups. ELISA results showed elevated levels of TNF-α and IL-6 in the ileum of the mice infected with WT and ΔphoPQC. In addition, deletion of the phoPQ gene in C. sakazakii resulted in a down-regulation of inflammatory genes (IL-1β, TNF-α, IL-6, NF-κB p65, TLR4) within the ileum and decreased inflammation by modulating the TLR4/NF-κB pathway. It is suggested that targeting the PhoP/PhoQ two-component system could be a potential strategy for mitigating C. sakazakii-induced neonatal infections.

Dysbiotic Vaginal Microbiota Induces Preterm Birth Cascade via Pathogenic Molecules in the Vagina

Dysbiotic vaginal microbiota (DVM) disturb the vaginal environment, including pH, metabolite, protein, and cytokine profiles. This study investigated the impact of DVM on the vaginal environment in 40 Korean pregnant women and identified predictable biomarkers of birth outcomes. Cervicovaginal fluid (CVF) samples were collected in the third trimester using vaginal swabs, examined for pH, and stored at -80 °C for further analysis. The samples were grouped as full-term (FTB, n = 20) and preterm (PTB, n = 20) births. The microbiota was profiled in the V1-V9 regions. The levels of targeted metabolites, TLR-4, and cytokines were determined. The pH of CVF from PTB (>4.5) was significantly higher than that of the CVF from FTB (>3.5) (p < 0.05). Neonatal gestational age at delivery, birth weight, and Apgar score differed significantly between groups. The relative abundances of beneficial Lactobacillus spp., such as Lactobacillus gasseri, Lactobacillus jensenii, and Bifidobacterium, were higher in FTB, whereas those of pathogenic Enterococcus faecalis, Staphylococcus, Prevotella, Ureaplasma parvum, and Corynebacterium spp. were higher in PTB. Acetate, methanol, TLR-4, and TNF-α levels were negatively correlated with gestational age at delivery and birth weight. Moreover, ethanol, methanol, TLR-4, IL-6, IL-1β, and TNF-α levels were positively correlated with succinate, acetate, acetoacetate, formate, and ammonia. Overall, DVM induces preterm birth via pathogenic molecules in the vagina.

Bifidobacterium and the intestinal mucus layer

Bifidobacterium species are integral members of the human gut microbiota and these microbes have significant interactions with the intestinal mucus layer. This review delves into Bifidobacterium-mucus dynamics, shedding light on the multifaceted nature of this relationship. We cover conserved features of Bifidobacterium-mucus interactions, such as mucus adhesion and positive regulation of goblet cell and mucus production, as well as species and strain-specific attributes of mucus degradation. For each interface, we explore the molecular mechanisms underlying these interactions and their potential implications for human health. Notably, we emphasize the ability of Bifidobacterium species to positively influence the mucus layer, shedding light on its potential as a mucin-builder and a therapeutic agent for diseases associated with disrupted mucus barriers. By elucidating the complex interplay between Bifidobacterium and intestinal mucus, we aim to contribute to a deeper understanding of the gut microbiota-host interface and pave the way for novel therapeutic strategies.

Infant Fecal Fermentations with Galacto-Oligosaccharides and 2′-Fucosyllactose Show Differential Bifidobacterium longum Stimulation at Subspecies Level

The objective of the current study was to evaluate the potential of 2′-FL and GOS, individually and combined, in beneficially modulating the microbial composition of infant and toddler (12–18 months) feces using the micro-Matrix bioreactor. In addition, the impacts of GOS and 2′-FL, individually and combined, on the outgrowth of fecal bifidobacteria at (sub)species level was investigated using the baby M-SHIME® model. For young toddlers, significant increases in the genera Bifidobacterium, Veillonella, and Streptococcus, and decreases in Enterobacteriaceae, Clostridium XIVa, and Roseburia were observed in all supplemented fermentations. In addition, GOS, and combinations of GOS and 2′-FL, increased Collinsella and decreased Salmonella, whereas 2′-FL, and combined GOS and 2′-FL, decreased Dorea. Alpha diversity increased significantly in infants with GOS and/or 2′-FL, as well as the relative abundances of the genera Veillonella and Akkermansia with 2′-FL, and Lactobacillus with GOS. Combinations of GOS and 2′-FL significantly stimulated Veillonella, Lactobacillus, Bifidobacterium, and Streptococcus. In all supplemented fermentations, Proteobacteria decreased, with the most profound decreases accomplished by the combination of GOS and 2′-FL. When zooming in on the different (sub)species of Bifidobacterium, GOS and 2’-FL were shown to be complementary in stimulating breast-fed infant-associated subspecies of Bifidobacterium longum in a dose-dependent manner: GOS stimulated Bifidobacterium longum subsp. longum, whereas 2′-FL supported outgrowth of Bifidobacterium longum subsp. infantis.

Leaky Gut and the Ingredients That Help Treat It: A Review

The human body is in daily contact with potentially toxic and infectious substances in the gastrointestinal tract (GIT). The GIT has the most significant load of antigens. The GIT can protect the intestinal integrity by allowing the passage of beneficial agents and blocking the path of harmful substances. Under normal conditions, a healthy intestinal barrier prevents toxic elements from entering the blood stream. However, factors such as stress, an unhealthy diet, excessive alcohol, antibiotics, and drug consumption can compromise the composition of the intestinal microbiota and the homeostasis of the intestinal barrier function of the intestine, leading to increased intestinal permeability. Intestinal hyperpermeability can allow the entry of harmful agents through the junctions of the intestinal epithelium, which pass into the bloodstream and affect various organs and systems. Thus, leaky gut syndrome and intestinal barrier dysfunction are associated with intestinal diseases, such as inflammatory bowel disease and irritable bowel syndrome, as well as extra-intestinal diseases, including heart diseases, obesity, type 1 diabetes mellitus, and celiac disease. Given the relationship between intestinal permeability and numerous conditions, it is convenient to seek an excellent strategy to avoid or reduce the increase in intestinal permeability. The impact of dietary nutrients on barrier function can be crucial for designing new strategies for patients with the pathogenesis of leaky gut-related diseases associated with epithelial barrier dysfunctions. In this review article, the role of functional ingredients is suggested as mediators of leaky gut-related disorders.

Protective Effects and Mechanism of a Novel Probiotic Strain Ligilactobacillus salivarius YL20 against Cronobacter sakazakii-Induced Necrotizing Enterocolitis In Vitro and In Vivo

Exposure to probiotics in early life contributes to host intestinal development and prevention of necrotizing enterocolitis (NEC). Cronobacter sakazakii (C. sakazakii), an opportunistic pathogen, can cause NEC, bacteremia, and meningitis in neonates, but the research of probiotics against C. sakazakii is limited relative to other enteropathogens. Here, the protective effect and mechanism of a novel probiotic Ligilactobacillus salivarius (L. salivarius) YL20 isolated from breast milk on C. sakazakii-induced intestinal injury were explored by using two in vitro models, including an C. sakazakii-infected intestinal organoid model and intestinal barrier model, as well as an in vivo experimental animal model. Our results revealed that L. salivarius YL20 could promote epithelial cell proliferation in intestinal organoids, rescue budding-impaired organoids, prevent the decrease of mRNA levels of leucine-rich repeat containing G protein-coupled receptor 5 (Lgr5), zonula occludens-1 (Zo-1) and Occludin, and reverse C. sakazakii-induced low level of Mucin 2 (MUC2) in intestinal organoids. Additionally, YL20 could inhibit C. sakazakii invasion, increase the expression of ZO-1 and occludin in C. sakazakii-infected HT-29 cells, and reverse TEER decrease and corresponding permeability increase across C. sakazakii-infected Caco-2 monolayers. Furthermore, YL20 administration could alleviate NEC in C. sakazakii-infected neonatal mice by increasing the mice survival ratio, decreasing pathology scores, and downregulating pro-inflammatory cytokines. Meanwhile, YL20 could also enhance intestinal barrier function in vivo by increasing the number of goblet cells, the level of MUC-2 and the expression of ZO-1. Our overall findings demonstrated for the first time the beneficial effects of L. salivarius YL20 against C. sakazakii-induced NEC by improving intestinal stem cell function and enhancing intestinal barrier integrity.

Intestinal Epithelial Barrier Function and Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is a major cause of morbidity and mortality in premature infants. NEC is characterized by intestinal tissue inflammation and necrosis. The intestinal barrier is altered in NEC, which potentially contributes to its pathogenesis by promoting intestinal bacterial translocation and stimulating the inflammatory response. In premature infants, many components of the intestinal barrier are immature. This article reviews the different components of the intestinal barrier and how their immaturity contributes to intestinal barrier dysfunction and NEC.

Role of Bifidobacteria on Infant Health

Bifidobacteria are among the predominant microorganisms during infancy, being a dominant microbial group in the healthy breastfed infant and playing a crucial role in newborns and infant development. Not only the levels of the Bifidobacterium genus but also the profile and quantity of the different bifidobacterial species have been demonstrated to be of relevance to infant health. Although no definitive proof is available on the causal association, reduced levels of bifidobacteria are perhaps the most frequently observed alteration of the intestinal microbiota in infant diseases. Moreover, Bifidobacterium strains have been extensively studied by their probiotic attributes. This review compiles the available information about bifidobacterial composition and function since the beginning of life, describing different perinatal factors affecting them, and their implications on different health alterations in infancy. In addition, this review gathers exhaustive information about pre-clinical and clinical studies with Bifidobacterium strains as probiotics in neonates.

Exopolysaccharides from Bifidobacterium animalis Ameliorate Escherichia coli-Induced IPEC-J2 Cell Damage via Inhibiting Apoptosis and Restoring Autophagy

Enteropathogenic Escherichia coli (EPEC) is a common zoonotic pathogen that causes acute infectious diarrhea. Probiotics like Bifidobacterium are known to help prevent pathogen infections. The protective effects of Bifidobacterium are closely associated with its secretory products exopolysaccharides (EPS). We explored the effects of the EPS from Bifidobacterium animalis subsp. lactis (B. lactis) on ameliorating the damage of an intestinal porcine epithelial cell line (IPEC-J2) during EPEC infection. Pretreatment with EPS alleviated EPEC-induced apoptosis through the restoration of cell morphology and the downregulation of protein expressions of cleaved-caspase 8, cleaved-caspase 3, and cleaved-PARP. EPS-mediated remission of apoptosis significantly improved cell viability during EPEC infection. EPEC infection also resulted in impaired autophagy, as demonstrated by decreased expressions of autophagy-related proteins Beclin 1, ATG5, and microtubule-binding protein light chain-3B (LC3B) and the increased expression of p62 through western blot analysis. However, EPS reversed these effects which indicated that EPS promoted autophagosome formation. Furthermore, EPS prevented the lysosome damage induced by EPEC as it enhanced lysosomal acidification and raised lysosome-associated protein levels, thus promoted autophagosome degradation. Our findings suggest that the amelioration of EPEC-induced cell damages by EPS is associated with the limitation of detrimental apoptosis and the promotion of autophagy flux.

Cronobacter sakazakii ATCC 29544 Translocated Human Brain Microvascular Endothelial Cells via Endocytosis, Apoptosis Induction, and Disruption of Tight Junction

Cronobacter sakazakii (C. sakazakii) is an emerging opportunistic foodborne pathogen that can cause neonatal necrotizing enterocolitis, meningitis, sepsis in neonates and infants with a relatively high mortality rate. Bacterial transcytosis across the human brain microvascular endothelial cells (HBMEC) is vital for C. sakazakii to induce neonatal meningitis. However, few studies focus on the mechanisms by which C. sakazakii translocates HBMEC. In this study, the translocation processes of C. sakazakii on HBMEC were explored. C. sakazakii strains could effectively adhere to, invade and intracellularly survive in HBMEC. The strain ATCC 29544 exhibited the highest translocation efficiency across HBMEC monolayer among four tested strains. Bacteria-contained intracellular endosomes were detected in C. sakazakii-infected HBMEC by a transmission electron microscope. Endocytosis-related proteins CD44, Rab5, Rab7, and LAMP2 were increased after infection, while the level of Cathepsin L did not change. C. sakazakii induced TLR4/NF-κB inflammatory signal pathway activation in HBMEC, with increased NO production and elevated mRNA levels of IL-8, IL-6, TNF-α, IL-1β, iNOS, and COX-2. C. sakazakii infection also caused LDH release, caspase-3 activation, and HBMEC apoptosis. Meanwhile, increased Dextran-FITC permeability and decreased trans epithelial electric resistance indicated that C. sakazakii disrupted tight junction of HBMEC monolayers, which was confirmed by the decreased levels of tight junction-related proteins ZO-1 and Occludin. These findings suggest that C. sakazakii induced intracellular bacterial endocytosis, stimulated inflammation and apoptosis, disrupted monolayer tight junction in HBMEC, which all together contribute to bacterial translocation.

The impact of indole-3-lactic acid on immature intestinal innate immunity and development: a transcriptomic analysis

An excessive intestinal inflammatory response may have a role in the pathogenesis of necrotizing enterocolitis (NEC) in very preterm infants. Indole-3-lactic acid (ILA) of breastmilk tryptophan was identified as the anti-inflammatory metabolite involved in probiotic conditioned media from Bifidobacteria longum subsp infantis. This study aimed to explore the molecular endocytic pathways involved in the protective ILA effect against inflammation. H4 cells, Caco-2 cells, C57BL/6 pup and adult mice were used to compare the anti-inflammatory mechanisms between immature and mature enterocytes in vitro and in vivo. The results show that ILA has pleiotropic protective effects on immature enterocytes including anti-inflammatory, anti-viral, and developmental regulatory potentials in a region-dependent and an age-dependent manner. Quantitative transcriptomic analysis revealed a new mechanistic model in which STAT1 pathways play an important role in IL-1β-induced inflammation and ILA has a regulatory effect on STAT1 pathways. These studies were validated by real-time RT-qPCR and STAT1 inhibitor experiments. Different protective reactions of ILA between immature and mature enterocytes indicated that ILA's effects are developmentally regulated. These findings may be helpful in preventing NEC for premature infants.

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.

Longitudinal Changes in Fecal Calprotectin Levels Among Pregnant Women With and Without Inflammatory Bowel Disease and Their Babies

BACKGROUND & AIMS

The effect of pregnancy on inflammatory bowel disease (IBD) remains poorly understood. We aimed to monitor intestinal inflammation using fecal calprotectin (FC) in pregnant women and their babies during early life.

METHODS

Pregnant women with or without IBD and their infants were prospectively enrolled. FC levels were measured at each trimester of pregnancy and in babies throughout the first 3 years of life. Repeated-measures analysis was applied to investigate changes in FC levels while adjusting for confounders. The FC levels were correlated with the bacterial abundance in both mothers and babies.

RESULTS

Six hundred and fourteen fecal samples from 358 mothers (98 with IBD) and 1005 fecal samples from 289 infants (76 born to IBD mothers) were analyzed. Pregnant Patients with IBD maintained higher FC levels through pregnancy compared with controls (P = 7.5 × 10^-54). FC gradually increased in controls and declined in Patients with IBD throughout pregnancy (P for interaction = 5.8 × 10^-7). Babies born to mothers with IBD presented with significantly higher FC levels than those born to controls up to 3 years of age, after adjusting for sex, delivery mode, feeding behavior, and antibiotics exposure (2 weeks to 3 months of age, P = .015; 12-36 months of age, P = .00003). Subdoligranulum, Roseburia, Fusicatenibacter, and Alistipes negatively correlated, and Streptococcus, Prevotella, Escherichia-Shigella, and Bifidobacterium positively correlated with maternal FC levels at T3. Faecalibacterium, Bifidobacterium, and Alistipes showed negative correlations, and Streptococcus were positively correlated with FC levels within 3 months of birth.

CONCLUSIONS

Pregnancy is associated with decreased inflammatory activity in mothers with IBD. Higher FC levels in babies born to mothers with IBD suggest subclinical inflammation in early life, the long-term consequences of which are uncertain.

Current and Future Perspectives on the Role of Probiotics, Prebiotics, and Synbiotics in Controlling Pathogenic Cronobacter Spp. in Infants

Cronobacter species, in particular C. sakazakii, is an opportunistic bacterial pathogen implicated in the development of potentially debilitating illnesses in infants (<12months old). The combination of a poorly developed immune system and gut microbiota put infants at a higher risk of infection compared to other age groups. Probiotics and prebiotics are incorporated in powdered infant formula and, in addition to strengthening gut physiology and stimulating the growth of commensal gut microbiota, have proven antimicrobial capabilities. Postbiotics in the cell-free supernatant of a microbial culture are derived from probiotics and can also exert health benefits. Synbiotics, a mixture of probiotics and prebiotics, may provide further advantages as probiotics and gut commensals degrade prebiotics into short-chain fatty acids that can provide benefits to the host. Cell-culture and animal models have been widely used to study foodborne pathogens, but sophisticated gut models have been recently developed to better mimic the gut conditions, thus giving a more accurate representation of how various treatments can affect the survival and pathogenicity of foodborne pathogens. This review aims to summarize the current understanding on the connection between Cronobacter infections and infants, as well as highlight the potential efficacy of probiotics, prebiotics, and synbiotics in reducing invasive Cronobacter infections during early infancy.

Short chain fatty acids produced by colonizing intestinal commensal bacterial interaction with expressed breast milk are anti-inflammatory in human immature enterocytes

Necrotizing enterocolitis (NEC) is a devastating intestinal emergency that affects ten percent of very low birth weight premature babies and costs society in both expense and heartache. It is probably caused by an inappropriate interaction of colonizing bacteria with an immature intestine. A possible preventative measure is to feed prematures their mother's expressed breast milk in conjunction with a probiotic. This synbiotic prevention reduces the severity and incidence of this condition. This study was designed to determine the mechanism of the synbiotic effect in human and mouse fetal intestine. Breast milk interacting with a NEC preventative probiotic such as Bifidobacterium infantis can produce increased levels of short chain fatty acids (acetate, propionate and butyrate) (SCFAs). SCFAs are known to be anti-inflammatory in mature enterocytes and immunocytes. Very little is known about their role in immature intestine. When exposed to a human fetal cell line, fetal intestinal organoids and fetal mouse intestine, these SCFAs were anti-inflammatory. Their mechanism of anti-inflammation differed from those reported for mature cells by involving the G-protein coupled receptor (GPR 109A) and inhibiting histone deacetylase 4 and 5. These bacterial metabolites may help explain the synbiotic anti-inflammatory effect of breast milk and probiotics given to premature infants at risk for NEC.

Prebiotics: tools to manipulate the gut microbiome and metabolome

The human gut is an ecosystem comprising trillions of microbes interacting with the host. The composition of the microbiota and their interactions play roles in different biological processes and in the development of human diseases. Close relationships between dietary modifications, microbiota composition and health status have been established. This review focuses on prebiotics, or compounds which selectively encourage the growth of beneficial bacteria, their mechanisms of action and benefits to human hosts. We also review advances in synthesis technology for human milk oligosaccharides, part of one of the most well-characterized prebiotic–probiotic relationships. Current and future research in this area points to greater use of prebiotics as tools to manipulate the microbial and metabolic diversity of the gut for the benefit of human health.

The developmentally regulated fetal enterocyte gene, ZP4, mediates anti-inflammation by the symbiotic bacterial surface factor polysaccharide A on Bacteroides fragilis

Initial colonizing bacteria play a critical role in completing the development of the immune system in the gastrointestinal tract of infants. Yet, the interaction of colonizing bacterial organisms with the developing human intestine favors inflammation over immune homeostasis. This characteristic of bacterial-intestinal interaction partially contributes to the pathogenesis of necrotizing enterocolitis (NEC), a devastating premature infant intestinal inflammatory disease. However, paradoxically some unique pioneer bacteria (initial colonizing species) have been shown to have a beneficial effect on the homeostasis of the immature intestine and the prevention of inflammation. We have reported that one such pioneer bacterium, Bacteroides fragilis (B. fragilis), and its surface component polysaccharide A (PSA) inhibit IL-1β-induced inflammation in a human primary fetal small intestinal cell line (H4 cells). In this study, using transcription profiling of H4 cellular RNA after pretreatment with or without PSA before an inflammatory stimulation of IL-1β, we have begun to further determine the cellular mechanism for anti-inflammation. We show that a developmentally regulated gene, zona pellucida protein 4 (ZP4), is uniquely elevated after IL-1β stimulation and reduced with PSA exposure. ZP4 was known as a sperm receptor-mediating species-specific binding protein in the initial life of mammals. However, its intestinal epithelial function is unclear. We found that ZP4 is a developmentally regulated gene involved with immune function and regulated by both Toll-like receptor 2 and 4. Knockdown of ZP4-affected PSA inhibited IL-8 mRNA expression in response to IL-1β. This represents an initial study of ZP4 innate immune function in immature enterocytes. This study may lead to new opportunity for efficient treatment of NEC.NEW & NOTEWORTHY This study extends previous observations to define the cellular mechanisms of polysaccharide A-induced anti-inflammation in immature enterocytes using transcription profiling of enterocyte genes after preexposure to polysaccharide A before an inflammatory stimulus with IL-1β.

Bacteroides fragilis Strain ZY-312 Defense against Cronobacter sakazakii-Induced Necrotizing Enterocolitis In Vitro and in a Neonatal Rat Model

Cronobacter sakazakii is an important pathogen associated with the development of necrotizing enterocolitis (NEC), infant sepsis, and meningitis. Several randomized prospective clinical trials demonstrated that oral probiotics could decrease the incidence of NEC. Previously, we isolated and characterized a novel probiotic, Bacteroides fragilis strain ZY-312. However, it remains unclear how ZY-312 protects the host from the effects of C. sakazakii infection. To understand the underlying mechanisms triggering the probiotic effects, we tested the hypothesis that there was cross talk between probiotics/probiotics-modulated microbiota and the local immune system, governed by the permeability of the intestinal mucosa, using in vitro and in vivo models for the intestinal permeability. The probiotic effects of ZY-312 on intestinal epithelial cells were first examined, and the results revealed that ZY-312 inhibited C. sakazakii invasion, C. sakazakii-induced dual cell death (pyroptosis and apoptosis), and epithelial barrier dysfunction in vitro and in vivo The presence of ZY-312 also resulted in decreased expression of an inflammasome (NOD-like receptor family member pyrin domain-containing protein 3 [NLRP3]), caspase-3, and serine protease caspase-1 in a neonatal rat model. Furthermore, ZY-312 significantly modulated the compositions of the intestinal bacterial communities and decreased the relative abundances of Proteobacteria and Gammaproteobacteria but increased the relative abundances of Bacteroides and Bacillus in neonatal rats. In conclusion, our findings have shown for the first time that the probiotic B. fragilis ZY-312 suppresses C. sakazakii-induced NEC by modulating the proinflammatory response and dual cell death (apoptosis and pyroptosis).IMPORTANCE Cronobacter sakazakii is an opportunistic pathogenic bacterium that can cause necrotizing enterocolitis (NEC). However, the mechanism of pathogenicity of C. sakazakii is largely unknown. Here we have now demonstrated that apoptotic and pyroptotic stimuli are effectors of C. sakazakii-induced NEC. Previously, we isolated a novel probiotic strain candidate from fecal samples from healthy infants and characterized it as Bacteroides fragilis strain ZY-312. Functional characterization reveals that ZY-312 inhibited C. sakazakii invasion, restoring epithelial barrier dysfunction, decreasing the expression of inflammatory cytokines, and reducing dual cell death (pyroptosis and apoptosis). Furthermore, the presence of ZY-132 was sufficient to hinder the adverse reaction seen with C. sakazakii in a C. sakazakii-induced NEC model. Taking the results together, our study demonstrated the utility of ZY-312 as a promising probiotic agent for the prevention of NEC.

Probiotics and the prevention of necrotizing enterocolitis

BACKGROUND

Immaturity of the host immune system and alterations in the intestinal microbiome appear to be key factors in the pathogenesis of necrotizing enterocolitis (NEC). The aim of this paper is to weigh the evidence for the use of probiotics to prevent NEC in premature infants.

METHODS

Animal studies, randomized controlled trials, observational cohort studies and meta-analyses involving administration of probiotic products for the prevention of NEC were reviewed. This review of the evidence summarizes the available preclinical and clinical data.

RESULTS

In animal models probiotic microbes alter the intestinal microbiome, decrease inflammation and intestinal permeability and decrease the incidence and severity of experimental NEC. In randomized, placebo-controlled trials and cohort studies of premature infants, probiotic microbes decrease the risk of NEC, death and sepsis.

CONCLUSION

Evidence is strong for the prevention of NEC with the use of combination probiotics in premature infants who receive breast milk. The potential risks and benefits of probiotic administration to premature infants should be carefully reviewed with parents.

TYPE OF STUDY

Therapeutic.

LEVEL OF EVIDENCE

I.

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.

Effects of probiotics on experimental necrotizing enterocolitis: a systematic review and meta-analysis

BackgroundMeta-analyses of randomized controlled trials (RCTs) suggest that probiotics decrease the risk of necrotizing enterocolitis (NEC) in preterm infants. Many animal RCTs have evaluated probiotics for preventing NEC. We systematically reviewed the literature on this topic.MethodsThe protocol for systematic review of animal intervention studies (SYRCLE) was followed. Medline, Embase, ISI Web of Science, e-abstracts from the Pediatric Academic Society meetings, and other neonatal conferences were searched in December 2015 and August 2016. RCTs comparing probiotics vs. placebo/no probiotic were included.ResultsA total of 29 RCTs were included (Rats: 16, Mice: 7, Piglets: 3, Quail: 2, Rabbit: 1; N~2,310), with 21 reporting on histopathologically confirmed NEC; remaining 8 assessed only pathways of probiotic benefits. Twenty of the 21 RCTs showed that probiotics significantly reduced NEC. Pooling of data was possible for 16/21 RCTs. Meta-analysis using random-effects model showed that probiotics significantly decreased the risk of NEC (203/641 (31.7%) vs. 344/571 (60.2%); relative risk: 0.51; 95% confidence interval (CI): 0.42-0.62; P<0.00001; I2=44%; number needed to treat: 4; 95% CI: 2.9, 4.3).ConclusionProbiotics significantly reduced NEC via beneficial effects on immunity, inflammation, tissue injury, gut barrier, and intestinal dysbiosis.

Colonization with Escherichia coli EC 25 protects neonatal rats from necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a significant cause of morbidity and mortality in premature infants; yet its pathogenesis remains poorly understood. To evaluate the role of intestinal bacteria in protection against NEC, we assessed the ability of naturally occurring intestinal colonizer E. coli EC25 to influence composition of intestinal microbiota and NEC pathology in the neonatal rat model. Experimental NEC was induced in neonatal rats by formula feeding/hypoxia, and graded histologically. Bacterial populations were characterized by plating on blood agar, scoring colony classes, and identifying each class by sequencing 16S rDNA. Binding of bacteria to, and induction of apoptosis in IEC-6 enterocytes were examined by plating on blood agar and fluorescent staining for fragmented DNA. E. coli EC 25, which was originally isolated from healthy rats, efficiently colonized the intestine and protected from NEC following introduction to newborn rats with formula at 10⁶ or 10⁸ cfu. Protection did not depend significantly on EC25 inoculum size or load in the intestine, but positively correlated with the fraction of EC25 in the microbiome. Introduction of EC25 did not prevent colonization with other bacteria and did not significantly alter bacterial diversity. EC25 neither induced cultured enterocyte apoptosis, nor protected from apoptosis induced by an enteropathogenic strain of Cronobacter muytjensii. Our results show that E. coli EC25 is a commensal strain that efficiently colonizes the neonatal intestine and protects from NEC.

Lactobacillus rhamnosus GG supernatant enhance neonatal resistance to systemic Escherichia coli K1 infection by accelerating development of intestinal defense

The objective of this study was to determine whether Lactobacillus rhamnosus GG culture supernatant (LCS) has a preventive effect against gut-derived systemic neonatal Escherichia coli (E. coli) K1 infection. The preventive effects were evaluated in human colonic carcinoma cell line Caco-2 and neonatal rat models. Our in vitro results showed that LCS could block adhesion, invasion and translocation of E. coli K1 to Caco-2 monolayer via up-regulating mucin production and maintaining intestinal integrity. In vivo experiments revealed that pre-treatment with LCS significantly decrease susceptibility of neonatal rats to oral E. coli K1 infection as reflected by reduced bacterial intestinal colonization, translocation, dissemination and systemic infections. Further, we found that LCS treated neonatal rats have higher intestinal expressions of Ki67, MUC2, ZO-1, IgA, mucin and lower barrier permeability than those in untreated rats. These results indicated that LCS could enhance neonatal resistance to systemic E. coli K1 infection via promoting maturation of neonatal intestinal defense. In conclusions, our findings suggested that LCS has a prophylactic effect against systemic E. coli K1 infection in neonates. Future studies aimed at identifying the specific active ingredients in LCS will be helpful in developing effective pharmacological strategies for preventing neonatal E. coli K1 infection.

Impact of probiotics on necrotizing enterocolitis

A large number of randomized placebo-controlled clinical trials and cohort studies have demonstrated a decrease in the incidence of necrotizing enterocolitis with administration of probiotic microbes. These studies have prompted many neonatologists to adopt routine prophylactic administration of probiotics while others await more definitive studies and/or probiotic products with demonstrated purity and stable numbers of live organisms. Cross-contamination and inadequate sample size limit the value of further traditional placebo-controlled randomized controlled trials. Key areas for future research include mechanisms of protection, optimum probiotic species or strains (or combinations thereof) and duration of treatment, interactions between diet and the administered probiotic, and the influence of genetic polymorphisms in the mother and infant on probiotic response. Next generation probiotics selected based on bacterial genetics rather than ease of production and large cluster-randomized clinical trials hold great promise for NEC prevention.

Probiotics in early life: a preventative and treatment approach

Microbial colonization of the infant gut plays a key role in immunological and metabolic pathways impacting human health. Since the maturation of the gut microbiota coincides with early life development, failure to develop a health compatible microbiota composition may result in pathology and disease in later life. Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. Maternal transfer of microorganisms is possible during pregnancy and lactation, and the mother's diet and microbiota can influence that of her offspring. Furthermore, pre-term birth, Caesarean section birth, formula feeding, antibiotic use, and malnutrition have been linked to dysbiosis, which in turn is associated with several pathologies such as necrotizing enterocolitis, inflammatory bowel diseases, antibiotic associated diarrhea, colic, and allergies. Thus, early life should represent a preferred stage of life for probiotic interventions. In this context, they could be regarded as a means to 'program' the individual for health maintenance, in order to prevent pathologies associated with dysbiosis. In order to elucidate the mechanisms underlying the benefits of probiotic administration, pre-clinical studies have been conducted and found an array of positive results such as improved microbial composition, intestinal maturation, decreased pathogenic load and infections, and improved immune response. Moreover, specific probiotic strains administered during the perinatal period have shown promise in attenuating severity of necrotizing enterocolitis. The mechanisms elucidated suggest that probiotic interventions in early life can be envisaged for disease prevention in both healthy offspring and offspring at risk of chronic disease.

A Role for cAMP and Protein Kinase A in Experimental Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is a devastating intestinal disease that has been associated with Cronobacter sakazakii and typically affects premature infants. Although NEC has been actively investigated, little is known about the mechanisms underlying the pathophysiology of epithelial injury and intestinal barrier damage. Cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) are important mediators and regulators of apoptosis. To test the hypothesis that C. sakazakii increases cAMP and PKA activation in experimental NEC resulting in increased epithelial apoptosis, we investigated the effects of C. sakazakii on cAMP and PKA in vitro and in vivo. Specifically, rat intestinal epithelial cells and a human intestinal epithelial cell line were infected with C. sakazakii, and cAMP levels and phosphorylation of PKA were measured. An increase in cAMP was demonstrated after infection, as well as an increase in phosphorylated PKA. Similarly, increased intestinal cAMP and PKA phosphorylation were demonstrated in a rat pup model of NEC. These increases were correlated with increased intestinal epithelial apoptosis. The additional of a PKA inhibitor (KT5720) significantly ameliorated these effects and decreased the severity of experimental NEC. Findings were compared with results from human tissue samples. Collectively, these observations indicate that cAMP and PKA phosphorylation are associated with increased apoptosis in NEC and that inhibition of PKA activation protects against apoptosis and experimental NEC.

Harvesting the benefits of biofilms: A novel probiotic delivery system for the prevention of necrotizing enterocolitis

BACKGROUND/PURPOSE

Probiotics reduce the incidence of necrotizing enterocolitis (NEC) albeit only when administered at high frequency (at least daily). We have developed a novel probiotic delivery system in which probiotics are grown as a biofilm on microspheres, allowing enhanced efficacy with only a single treatment.

METHODS

Neonatal rats were subjected to experimental NEC. Pups received a single enteral dose of: (1) vehicle only, (2) unloaded microspheres, (3) MRS (broth)-loaded microspheres, (4) Lactobacillus reuteri, (5) L. reuteri grown on unloaded microspheres, or (6) L. reuteri grown on MRS-loaded microspheres. Intestinal injury was graded histologically and intestinal permeability determined by serum levels of enterally administered fluorescein isothiocyanate-labeled dextran.

RESULTS

69% of untreated pups developed NEC, whereas 32% of pups treated with L. reuteri grown as a biofilm on unloaded microspheres (p=0.009) and 33% of pups treated with L. reuteri grown as a biofilm on MRS-loaded microspheres (p=0.005) developed NEC. No other group had a significant reduction in NEC. Furthermore, pups treated with L. reuteri grown as a biofilm had significantly reduced intestinal permeability.

CONCLUSIONS

A single dose of Lactobacillus biofilm grown on biocompatible microspheres significantly reduces NEC incidence and severity. This novel probiotic delivery system may be beneficial in the prevention of NEC in the future.

Probiotics and Innate and Adaptive Immune Responses in Premature Infants

Premature infants are at increased risk for morbidity and mortality due to necrotizing enterocolitis (NEC) and sepsis. Probiotics decrease the risk of NEC and death in premature infants; however, mechanisms of action are unclear. A wide variety of probiotic species have been evaluated for potential beneficial properties in vitro, in animal models, and in clinical trials of premature infants. Although there is variation by species and even strain, common mechanisms of protection include attenuation of intestinal inflammation, apoptosis, dysmotility, permeability, supplanting other gut microbes through production of bacteriocins, and more effective use of available nutrients. Here, we review the most promising probiotics and what is known about their impact on the innate and adaptive immune response.

Cultivating healthy growth and nutrition through the gut microbiota

Microbiota assembly is perturbed in children with undernutrition, resulting in persistent microbiota immaturity that is not rescued by current nutritional interventions. Evidence is accumulating that this immaturity is causally related to the pathogenesis of undernutrition and its lingering sequelae. Preclinical models in which human gut communities are replicated in gnotobiotic mice have provided an opportunity to identify and predict the effects of different dietary ingredients on microbiota structure, expressed functions, and host biology. This capacity sets the stage for proof-of-concept tests designed to deliberately shape the developmental trajectory and configurations of microbiota in children representing different geographies, cultural traditions, and states of health. Developing these capabilities for microbial stewardship is timely given the global health burden of childhood undernutrition, the effects of changing eating practices brought about by globalization, and the realization that affordable nutritious foods need to be developed to enhance our capacity to cultivate healthier microbiota in populations at risk for poor nutrition.

Secreted Metabolites of Bifidobacterium infantis and Lactobacillus acidophilus Protect Immature Human Enterocytes from IL-1β-Induced Inflammation: A Transcription Profiling Analysis

Combination regimens of Bifidobacterium infantis and Lactobacillus acidophilus have been demonstrated to prevent necrotizing enterocolitis (NEC) in clinical trials. However, the molecular mechanisms responsible for this protective effect are not well understood. Additionally, conditioned media from individual cultures of these two probiotics show strain specific modulation of inflammation using in vitro human intestinal NEC models. Here we report a transcription profiling analysis of gene expression in immature human fetal intestinal epithelial cells (H4 cells) pretreated with conditioned media from B. infantis (BCM) or L. acidophilus (LCM) prior to IL-1β stimulation. Compared with control media, the two probiotic-conditioned media (PCM) treatments altered the expression of hundreds of genes involved in the immune response, apoptosis and cell survival, cell adhesion, the cell cycle, development and angiogenesis. In IL-1β-stimulated cells, PCM treatment decreased the upregulation of genes in the NF-κB activation pathway and downregulated genes associated with extracellular matrix (ECM) remodeling. Compared with LCM, BCM showed more significant modulatory effects on ECM remodeling, reflected by a lower p value. IL-6 and IL-8 production was significantly reduced in IL-1β-stimulated cells pretreated with PCM (p<0.05), which was consistent with their altered gene expression. Western blot analysis showed that compared with IL-1β stimulation alone, PCM treatment attenuated the decrease of cytoplasmic IκBα and NF-κB p65 levels as well as the increase of nuclear NF-κB p65 levels in the stimulated cells (p<0.05). In conclusion, PCM treatment exerted anti-inflammatory effects in immature human fetal enterocytes primarily by modulating genes in the NF-κB signaling and ECM remodeling pathways. Additionally, some components of these signaling pathways, particularly the ECM remodeling pathway, were more profoundly affected by BCM than LCM.

Longitudinal analysis of the premature infant intestinal microbiome prior to necrotizing enterocolitis: a case-control study

Necrotizing enterocolitis (NEC) is an inflammatory disease of the newborn bowel, primarily affecting premature infants. Early intestinal colonization has been implicated in the pathogenesis of NEC. The objective of this prospective case-control study was to evaluate differences in the intestinal microbiota between infants who developed NEC and unaffected controls prior to disease onset. We conducted longitudinal analysis of the 16S rRNA genes of 312 samples obtained from 12 NEC cases and 26 age-matched controls with a median frequency of 7 samples per subject and median sampling interval of 3 days. We found that the microbiome undergoes dynamic development during the first two months of life with day of life being the major factor contributing to the colonization process. Depending on when the infant was diagnosed with NEC (i.e. early vs. late onset), the pattern of microbial progression was different for cases and controls. The difference in the microbiota was most overt in early onset NEC cases and controls. In proximity to NEC onset, the abundances of Clostridium sensu stricto from Clostridia class were significantly higher in early onset NEC subjects comparing to controls. In late onset NEC, Escherichia/Shigella among Gammaproteobacteria, showed an increasing pattern prior to disease onset, and was significantly higher in cases than controls six days before NEC onset. Cronobacter from Gammaproteobacteria was also significantly higher in late onset NEC cases than controls 1-3 days prior to NEC onset. Thus, the specific infectious agent associated with NEC may vary by the age of infant at disease onset. We found that intravenously administered antibiotics may have an impact on the microbial diversity present in fecal material. Longitudinal analysis at multiple time points was an important strategy utilized in this study, allowing us to appreciate the dynamics of the premature infant intestinal microbiome while approaching NEC at various points.

Breast milk, microbiota, and intestinal immune homeostasis

Newborns adjust to the extrauterine environment by developing intestinal immune homeostasis. Appropriate initial bacterial colonization is necessary for adequate intestinal immune development. An environmental determinant of adequate colonization is breast milk. Although the full-term infant is developmentally capable of mounting an immune response, the effector immune component requires bacterial stimulation. Breast milk stimulates the proliferation of a well-balanced and diverse microbiota, which initially influences a switch from an intrauterine TH2 predominant to a TH1/TH2 balanced response and with activation of T-regulatory cells by breast milk-stimulated specific organisms (Bifidobacteria, Lactobacillus, and Bacteroides). As an example of its effect, oligosaccharides in breast milk are fermented by colonic bacteria producing an acid milieu for bacterial proliferation. In addition, short-chain fatty acids in breast milk activate receptors on T-reg cells and bacterial genes, which preferentially mediate intestinal tight junction expression and anti-inflammation. Other components of breast milk (defensins, lactoferrin, etc.) inhibit pathogens and further contribute to microbiota composition. The breast milk influence on initial intestinal microbiota also prevents expression of immune-mediated diseases (asthma, inflammatory bowel disease, type 1 diabetes) later in life through a balanced initial immune response, underscoring the necessity of breastfeeding as the first source of nutrition.

Bifidobacterium longum subspecies infantis: champion colonizer of the infant gut

Oligosaccharides are abundant in human milk. Production of these highly diverse structures requires significant energy expenditure by the mother and yet these human milk oligosaccharides offer no direct nutritive value to her infant. A primary function of human milk oligosaccharides is to shape the infant's intestinal microbiota with life-long consequences. Bifidobacterium longum subspecies infantis (B. infantis) is unique among gut bacteria in its prodigious capacity to digest and consume any human milk oligosaccharide structure, the result of a large repertoire of bacterial genes encoding an array of glycosidases and oligosaccharide transporters not found in other bacterial species. In vitro, B. infantis grows better than other bacterial strains in the presence of human milk oligosaccharides, displays anti-inflammatory activity in premature intestinal cells, and decreases intestinal permeability. In premature infants, B. infantis given in combination with human milk increases B. infantis and decreases Enterobacteriaceae in the feces. Probiotics containing B. infantis decrease the risk of necrotizing enterocolitis in premature infants. Colonization with B. infantis is also associated with increased vaccine responses. Probiotic organisms have historically been selected based on ease of production and stability. The advantages of B. infantis, selected through coevolution with human milk glycans, present an opportunity for focused manipulation of the infant intestinal microbiota.

Intestinal colonization and programming of the intestinal immune response

Initial bacterial colonization of the gut is a vital component of the development of the gastrointestinal tract, particularly mucosal immune protection, during the neonatal period. Newborn infants in their protected intrauterine environment are suddenly thrust into a highly contaminated extrauterine state. Although mucosal host defenses have developed in utero during fetal maturation because of the stimulation of ingested trophic factors in amniotic fluid, actual active protection only occurs when colonizing bacteria stimulate the gut mucosal barrier. Colonization evolves over a period of about 1 year and is dependent on the mode of delivery, use of perinatal antibiotics, age at birth, and infant feeding. A fully colonized gut consists of 10(14) bacteria, establishes a symbiotic relationship with the host and insures normal development and immune homeostasis. Colonizing bacteria can also affect the epithelial mucosal barrier and the innate and adaptive immune systems. Disruption of normal colonization, dysbiosis, is associated with increased expression of disease. Evidence exists that the use of probiotics with dysbiosis may prevent disease expression.