Probiotics and other preventative strategies for necrotising enterocolitis

Microbes, Immunity, and Behavior: Psychoneuroimmunology Meets the Microbiome

There is now a large volume of evidence to support the view that the immune system is a key communication pathway between the gut and brain, which plays an important role in stress-related psychopathologies and thus provides a potentially fruitful target for psychotropic intervention. The gut microbiota is a complex ecosystem with a diverse range of organisms and a sophisticated genomic structure. Bacteria within the gut are estimated to weigh in excess of 1 kg in the adult human and the microbes within not only produce antimicrobial peptides, short chain fatty acids, and vitamins, but also most of the common neurotransmitters found in the human brain. That the microbial content of the gut plays a key role in immune development is now beyond doubt. Early disruption of the host-microbe interplay can have lifelong consequences, not just in terms of intestinal function but in distal organs including the brain. It is clear that the immune system and nervous system are in continuous communication in order to maintain a state of homeostasis. Significant gaps in knowledge remain about the effect of the gut microbiota in coordinating the immune-nervous systems dialogue. However, studies using germ-free animals, infective models, prebiotics, probiotics, and antibiotics have increased our understanding of the interplay. Early life stress can have a lifelong impact on the microbial content of the intestine and permanently alter immune functioning. That early life stress can also impact adult psychopathology has long been appreciated in psychiatry. The challenge now is to fully decipher the molecular mechanisms that link the gut microbiota, immune, and central nervous systems in a network of communication that impacts behavior patterns and psychopathology, to eventually translate these findings to the human situation both in health and disease. Even at this juncture, there is evidence to pinpoint key sites of communication where gut microbial interventions either with drugs or diet or perhaps fecal microbiota transplantation may positively impact mental health.

Development of the preterm gut microbiome in twins at risk of necrotising enterocolitis and sepsis

The preterm gut microbiome is a complex dynamic community influenced by genetic and environmental factors and is implicated in the pathogenesis of necrotising enterocolitis (NEC) and sepsis. We aimed to explore the longitudinal development of the gut microbiome in preterm twins to determine how shared environmental and genetic factors may influence temporal changes and compared this to the expressed breast milk (EBM) microbiome. Stool samples (n = 173) from 27 infants (12 twin pairs and 1 triplet set) and EBM (n = 18) from 4 mothers were collected longitudinally. All samples underwent PCR-DGGE (denaturing gradient gel electrophoresis) analysis and a selected subset underwent 454 pyrosequencing. Stool and EBM shared a core microbiome dominated by Enterobacteriaceae, Enterococcaceae, and Staphylococcaceae. The gut microbiome showed greater similarity between siblings compared to unrelated individuals. Pyrosequencing revealed a reduction in diversity and increasing dominance of Escherichia sp. preceding NEC that was not observed in the healthy twin. Antibiotic treatment had a substantial effect on the gut microbiome, reducing Escherichia sp. and increasing other Enterobacteriaceae. This study demonstrates related preterm twins share similar gut microbiome development, even within the complex environment of neonatal intensive care. This is likely a result of shared genetic and immunomodulatory factors as well as exposure to the same maternal microbiome during birth, skin contact and exposure to EBM. Environmental factors including antibiotic exposure and feeding are additional significant determinants of community structure, regardless of host genetics.

Probiotics for the prevention of necrotizing enterocolitis in neonates: an 8-year retrospective cohort study

WHAT IS KNOWN AND OBJECTIVE

Probiotic therapy has been shown to reduce morbidity and mortality of necrotizing enterocolitis (NEC) in premature infants in several international studies using various probiotic agents. The purpose of this study(*) is to describe our experience of using probiotic therapy in preventing NEC in infants with very low birth weight (VLBW) in a neonatal intensive care unit (NICU) and to evaluate whether our records provide evidence of effectiveness for probiotic therapy.

METHODS

In a retrospective cohort study, the efficacy of probiotic therapy in preventing NEC in VLBW infants was investigated via chart review. A probiotic administration protocol using a three-strain (Streptococcus thermophilus, Bifidobacterium infantis and Bifidobacterium bifidum) supplement was implemented in August 2007. Patients admitted to the NICU from August 2003 through July 2011 were screened. Primary outcomes are the morbidity and mortality of NEC. The secondary outcomes were severity of NEC and incidence of where infant feeds were stopped but NEC was not diagnosed (NEC scare).

RESULTS AND DISCUSSION

There was a significant increased baseline risk of NEC development in the probiotics group, including younger gestational age, higher incidence of patent ductus arteriosus (PDA) and use of indomethacin. The incidence of NEC is similar between the control group (2·8%) and probiotics group (2·4%) (hazard ratio, 1·15; 95% confidence interval [CI], 0·42, 3·12). Mortality of NEC is also not statistically different. Incidence of NEC scare was decreased from 2·8% in control group to 1·4% in probiotics group, although the difference was not statistically significant (P = 0·38).

WHAT IS KNOWN AND CONCLUSION

Our findings suggest that probiotics are safe in NEC prevention in VLBW infants. We had no cases of infection related to the strains of bacteria used in our product. With the low incidence of NEC (2·8%) and NEC scare (2·8%) in our cohort, we do not have enough power to detect any change in outcome, particularly as our study was observational. However, it is hoped that our data give useful information for others on probiotic prophylactic therapy in the routine clinical management of VLBW infants.

Bacterial and fungal viability in the preterm gut: NEC and sepsis

BACKGROUND AND AIMS

Evidence suggests that microbial communities in the preterm gut may influence the development of necrotising enterocolitis (NEC) and sepsis. Existing data often neglect fungi and whether bacteria were metabolically active or not. We sought to characterise the bacterial and fungal stool flora of preterm neonates and organism viability and evaluate any associations with NEC and sepsis.

PATIENTS

136 stools from 32 patients (<32 weeks gestation) were collected between birth and day 95. Seven infants developed NEC and 13 sepsis.

METHODS

Stools were analysed by PCR-DGGE for assessment of the total bacterial and fungal communities by analysis of 16S rRNA and 28S rRNA, respectively. In 65 samples (25 infants), the viable (RNA) bacterial and fungal communities were analysed. Analyses were performed to examine the possible effects of demographic or treatment related factors and the development of NEC or sepsis.

RESULTS

80 (66 viable) bacterial species were identified overall and 12 fungal (none viable). Total bacterial communities significantly differed between healthy infants and those with NEC or sepsis, with Sphingomonas spp. significantly associated with NEC. Significant drivers of community structure differed based on either total or viable analysis. Antifungal prophylaxis was associated with altered bacterial community and a reduction in bacterial richness was observed in week 4, correlating with high antibiotic exposure.

CONCLUSIONS

Total and viable communities differ in preterm infants, and non-viable fungal species are present in infants on fungal prophylaxis. Exploration of viability and non-bacterial contributors to the total community may increase understanding of NEC and sepsis.

Lactoferrin: Antimicrobial activity and therapeutic potential

Lactoferrin is a highly conserved protein from an evolutionary perspective, with a wide range of roles related to protection from infection and promotion of nutritional status. Infection, malnutrition and intestinal pathologies are key inter-related problems, represent important threats to survival and are associated with adverse long-term health outcomes after preterm birth. Lactoferrin is available as a commercial extract from bovine milk and offers potential as a therapeutic intervention for preterm infants modulating infections and intestinal pathologies. In this review we explore the structure, direct antimicrobial effects, modification of host immune function and gastrointestinal effects of lactoferrin. Current trial data are reviewed, and research priorities and challenges identified and discussed.

Microbiota diversity and stability of the preterm neonatal ileum and colon of two infants

The composition of the microbiota associated with the human ileum and colon in the early weeks of life of two preterm infants was examined, with particular emphasis on the Lactobacillus and Bifidobacterium members. Culturing work showed that bifidobacteria and lactobacilli in the ileostomy changed over time, compared with the colostomy effluent where there was far less variation. The colostomy infant was dominated by two phyla, Actinobacteria and Firmicutes, while in the ileostomy samples, Proteobacteria emerged at the expense of Actinobacteria. Bacteroidetes were only detected following the reversal of the ileostomy in the final fecal sample and were not detected in any colonic fluid samples. Clostridia levels were unstable in the colostomy fluid, suggesting that the ileostomy/colostomy itself influenced the gut microbiota, in particular the strict anaerobes. Pyrosequencing analysis of microbiota composition indicated that bifidobacteria and lactobacilli are among the dominant genera in both the ileal and colonic fluids. Bifidobacteria and lactobacilli levels were unstable in the ileostomy fluid, with large reductions in numbers and relative proportions of both observed. These decreases were characterized by an increase in proportions of Streptococcus and Enterobacteriaceae. Clostridium was detected only in the colonic effluent, with large changes in the relative proportions over time.

The preterm gut microbiota: changes associated with necrotizing enterocolitis and infection

AIM

To describe gut colonization in preterm infants using standard culture and 16S gene rRNA profiling, exploring differences in healthy infants and those who developed NEC/late onset sepsis (LOS).

METHODS

Ninety-nine stools from 38 infants of median 27-week gestation were cultured; 44 stools from 27 infants had their microbial profiles determined by 16S. Ordination analyses explored effects of patient variables on gut communities.

RESULTS

Standard microbiological culture identified a mean of two organisms (range 0-7), DGGE 12 (range 3-18) per patient. Enterococcus faecalis and coagulase negative staphylococci (CONS) were most common by culture (40% and 39% of specimens). Meconium was not sterile. No fungi were cultured. Bacterial community structures in infants with NEC and LOS differed from healthy infants. Infants who developed NEC carried more CONS (45% vs 30%) and less Enterococcus faecalis (31% vs 57%). 16S identified Enterobacter and Staphylococcus presence associated with NEC/LOS, respectively.

CONCLUSIONS

Important differences were found in the gut microbiota of preterm infants who develop NEC/LOS. The relationship of these changes to current practices in neonatal intensive care requires further exploration.

Screening for probiotic properties of strains isolated from feces of various human groups

The present study searched for potential probiotic strains from various human fecal samples. A total of 67 aerobic and 38 anaerobic strains were isolated from 5 different categories of human feces. Systematic procedures were used to evaluate the probiotic properties of the isolated strains. These showed about 75-97% survivability in acidic and bile salt environments. Adhesion to intestinal cell line Caco-2 was also high. The isolates exhibited hydrophobic properties in hexadecane. The culture supernatants of these strains showed antagonistic effects against pathogens. The isolates were resistant to a simulated gastrointestinal environment in vitro. Of the 4 best isolates, MAbB4 (Staphylococcus succinus) and FIdM3 (Enterococcus fecium), were promising candidates for a potential probiotic. S. succinus was found to be a probiotic strain, which is the second such species reported to date in this particular genus. A substantial zone of inhibition was found against Salmonella spp., which adds further support to the suggestion that the probiotic strain could help prevent intestinal infection. This study suggested that the human flora itself is a potential source of probiotics.

Oral probiotics: Lactobacillus sporogenes for prevention of necrotizing enterocolitis in very low-birth weight infants: a randomized, controlled trial

BACKGROUND/OBJECTIVE

The identification of probiotic species involved in gut homeostasis and their potential therapeutic benefits have led to an interest in their use for preventing necrotizing enterocolitis (NEC). Although bifidobacterium and lactobacilli sp. have been used to reduce the incidence of NEC in clinical trials. Lactobacillus sporogenes has not been used in the prevention of NEC in very low-birth weight infants yet. The objective of this study was to evaluate the efficacy of orally administered L sporogenes in reducing the incidence and severity of NEC in very low-birth weight (VLBW) infants.

SUBJECTS/METHODS

A prospective, blinded, randomized controlled trial was conducted in preterm infants with a gestational age of <33 weeks or birth weight of <1500 g. VLBW infants who survived to start enteral feeding were randomized into two groups The infants in the study group were given L. sporogenes with a dose of 350,000,000 c.f.u. added to breast milk or formula, once a day, starting with the first feed until discharged. The infants in the control group were fed without L. sporogenes supplementation. The primary outcome measurement was death or NEC (Bell's stage ≥2).

RESULTS

A total of 221 infants were studied: 110 in the study group and 111 in the control group. There was no significant difference in the incidence of death or NEC between the groups. Feeding intolerance was significantly lower in the probiotics group than in the control group (44.5% (n: 49) vs 63.1% (n: 70), respectively; P=0.006).

CONCLUSIONS

L. sporogenes supplementation at the dose of 350,000,000 c.f.u/day is not effective in reducing the incidence of death or NEC in VLBW infants, however, it could improve the feeding tolerance.

Enteral glutamine and/or arginine supplementation have favorable effects on oxidative stress parameters in neonatal rat intestine

OBJECTIVE

To investigate and compare the effects of enteral glutamine and arginine supply on lipid peroxidation and antioxidant enzyme levels in the small intestine of healthy breast-fed rats.

MATERIALS AND METHODS

The study comprised 40 newborn Sprague-Dawley rats born to 5 mother rats. Newborn rats were randomly divided into 4 groups. Starting from day 1 until day 21, group I received only breast milk; group II received breast milk and 200 mg/kg/day oral glutamine; group III received breast milk and 200 mg/kg/day oral arginine; and group IV received breast milk, 200 mg/kg/day glutamine, and 200 mg/kg/day arginine. Malondialdehyde levels and glutathione peroxidase (GPx) and superoxide dismutase activities were measured.

RESULTS

The lowest malondialdehyde levels were found in group II (P = 0.0001). Superoxide dismutase activity was found to be significantly higher in group II than group I (P < 0.001). Of the 4 groups, GPx activity was highest in group IV. GPx activity in group II was significantly higher than in group I (P = 0.001) or group III (P = 0.001). GPx activity was higher in group IV than in group I (P = 0.001) or group III (P = 0.001).

CONCLUSIONS

Enteral glutamine alone or in the presence of arginine has favorable effects on oxidative stress not only in experimental models of hypoxia-reoxygenation, but also in healthy newborn rats. This suggests that in premature neonates with insufficient oxidative resistance, glutamine and arginine supplementation may help prevent necrotizing enterocolitis.

Biomarkers for infants at risk for necrotizing enterocolitis: clues to prevention?

Necrotizing enterocolitis (NEC) is the most common severe gastrointestinal emergency that affects premature newborns. This disease often has a rapid onset with few, if any, antecedent signs that can be used to reliably predict its occurrence. Its rapid onset and progression to death, as well as its severe morbidity when the infant survives, begs for early diagnostic tools that may be used in determining those infants who would be at greatest risk for development of the disease and for whom early preventative measures could be targeted. Although studies have suggested efficacy of several techniques such as breath hydrogen, inflammatory mediators in blood, urine or stool, and genetic markers, these all have drawbacks limiting their use. The application of newly developed "omic" approaches may provide biomarkers for early diagnosis and targeted prevention of this disease.

Lactobacillus bulgaricus prevents intestinal epithelial cell injury caused by Enterobacter sakazakii-induced nitric oxide both in vitro and in the newborn rat model of necrotizing enterocolitis

Enterobacter sakazakii is an emerging pathogen that has been associated with outbreaks of necrotizing enterocolitis (NEC) as well as infant sepsis and meningitis. Our previous studies demonstrated that E. sakazakii induces NEC in a newborn rat model by inducing enterocyte apoptosis. However, the mechanisms responsible for enterocyte apoptosis are not known. Here we demonstrate that E. sakazakii induces significant production of nitric oxide (NO) in rat intestinal epithelial cells (IEC-6) upon infection. The elevated production of NO, which is due to increased expression of inducible NO synthase, is responsible for apoptosis of IEC-6 cells. Notably, pretreatment of IEC-6 cells with Lactobacillus bulgaricus (ATCC 12278) attenuated the upregulation of NO production and thereby protected the cells from E. sakazakii-induced apoptosis. Furthermore, pretreatment with L. bulgaricus promoted the integrity of enterocytes both in vitro and in the infant rat model of NEC, even after challenge with E. sakazakii. Infection of IEC-6 cells with E. sakazakii upregulated several genes related to apoptosis, cytokine production, and various signaling pathways, as demonstrated by rat gene array analysis, and this upregulation was subdued by pretreatment with L. bulgaricus. In agreement with these data, L. bulgaricus pretreatment protected newborn rats infected with E. sakazakii from developing NEC, resulting in improved survival.