Stool microflora in extremely low birthweight infants

Gastrointestinal function development and microbiota

The intestinal microbiota plays an important role in the development of post-natal gastrointestinal functions of the host. Recent advances in our capability to identify microbes and their function offer exciting opportunities to evaluate the complex cross talk between microbiota, intestinal barrier, immune system and the gut-brain axis. This review summarizes these interactions in the early colonization of gastrointestinal tract with a major focus on the role of intestinal microbiota in the pathogenesis of feeding intolerance in preterm newborn. The potential benefit of early probiotic supplementation opens new perspectives in case of altered intestinal colonization at birth as preventive and therapeutic agents.

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.

Probiotics and prebiotics: role in prevention of nosocomial sepsis in preterm infants

Nosocomial sepsis is associated with increased mortality and morbidity including neurodevelopmental impairment and prolonged hospital stay. Prevention of sepsis especially in the preterm infants in the neonatal intensive care unit remains a major challenge. The gastrointestinal tract is an important source of potential pathogens causing nosocomial sepsis as the immature intestinal epithelium can permit translocation of bacteria and yeast. The intestinal tract and its microflora play an important role in the immunity. Altering the gut microflora has been extensively studied for immunomodulation in preterm infants. Probiotics are live microorganisms which when administered in adequate amounts confer a health benefit on the host. Probiotics have been used for prevention and treatment of various medical conditions in children and adults. Studies on probiotics in premature infants have focused on normalizing intestinal flora, improvement in feeding intolerance, prevention of necrotizing enterocolitis and sepsis. In this paper, we discuss the intestinal bacterial colonization pattern; the rational for probiotics and prebiotic therapy with special focus on the prevention of nosocomial sepsis in preterm infants.

Identification and functional characterization of a novel monotreme- specific antibacterial protein expressed during lactation

Monotremes are the only oviparous mammals and exhibit a fascinating combination of reptilian and mammalian characters. They represent a component of synapsidal reproduction by laying shelled eggs which are incubated outside the mother’s body. This is accompanied by a prototherian lactation process, marking them as representatives of early mammals. The only extant monotremes are the platypus, and the short- and long- beaked echidnas, and their distributions are limited to Australia and New Guinea. Apart for a short weaning period, milk is the sole source of nutrition and protection for the hatchlings which are altricial and immunologically naive. The duration of lactation in these mammals is prolonged relative to the gestational length and period of incubation of eggs. Much of the development of monotreme young occurs in the non-sterile ex-utero environment. Therefore the role of milk in the growth, development and disease protection of the young is of significant interest. By sequencing the cDNA of cells harvested from monotreme milk, we have identified a novel monotreme- specific transcript, and the corresponding gene was designated as the EchAMP. The expression profile of this gene in various tissues revealed that it is highly expressed in milk cells. The peptides corresponding to the EchAMP protein have been identified in a sample of echidna milk In silico analysis indicated putative antimicrobial potential for the cognate protein of EchAMP. This was further confirmed by in vitro assays using a host of bacteria. Interestingly, EchAMP did not display any activity against a commensal gut floral species. These results support the hypothesis of enhancement of survival of the young by antimicrobial bioactives of mammary gland origin and thus emphasize the protective, non- nutritional role of milk in mammals.

Molecular characterization of bacterial colonization in the preterm and term infant's intestine

OBJECTIVE

To further define patterns of colonising intestinal microflora in newborn infants utilising molecular methods.

METHODS

Ten term and 5 preterm (<32 wk) infants born at the Royal Hospital for Women, Sydney, Australia were enrolled in the present study and followed for 6 mo post partum. Serial stools were collected, DNA was extracted and subjected to PCR-Denaturing Gradient Gel Electrophoresis using a range of primers and sequencing. The effect of gestational length, feeding and delivery method was compared to the pattern of bacterial acquisition.

RESULTS

Intestinal bacterial diversity was lower in preterm compared with term infants. For term infants, bacterial DNA detection rates were not associated with feeding or delivery method, although Enterobacteria and Clostridia were commonly identified. The detection rate of Bifidobacteria was lower in preterm infants than term infants. Potential pathogens were detected in preterm infant samples.

CONCLUSIONS

Preterm infants frequently have aberrant bacterial colonization of the intestine. Further research is now required to determine if this may contribute to adverse health outcomes.

Normal neonatal microbiome variation in relation to environmental factors, infection and allergy

PURPOSE OF REVIEW

Bacterial colonization of the infant intestinal tract begins at birth. We are at the forefront of understanding complex relationships between bacteria and multiple parameters of health of the developing infant. Moreover, the establishment of the microbiome in the critical neonatal period is potentially foundational for lifelong health and disease susceptibility. Recent studies utilizing state-of-the-art culture-independent technologies have begun to increase our knowledge about the gut microbiome in infancy, the impact of multiple exposures, and its effects on immune response and clinical outcomes such as allergy and infection.

RECENT FINDINGS

Postnatal exposures play a central role in the complex interactions between the nearly blank canvas of the neonatal intestine, whereas genetic factors do not appear to be a major factor. Infant microbial colonization is affected by delivery mode, dietary exposures, antibiotic exposure, and environmental toxicants. Successive microbiome acquisition in infancy is likely a determinant of early immune programming, subsequent infection, and allergy risk.

SUMMARY

The novel investigation of the neonatal microbiome is beginning to unearth substantial information, with a focus on immune programming that coevolves with the developing microbiome early in life. Several exposures common to neonatal and infant populations could exert pressure on the development of the microbiome and major diseases including allergy and infection in large populations.

Human β-defensin 2 expression in ELBW infants with severe necrotizing enterocolitis

BACKGROUND

The aim of this study was to analyze whether the mucosal innate immune response of extremely-low-birth-weight (ELBW) infants might play a role in the development of necrotizing enterocolitis (NEC).

METHODS

Between April 2008 and December 2009 antimicrobial peptides were prospectively measured in fecal samples of ELBW infants. In cases requiring abdominal surgery, full-thickness gut biopsies were analyzed for expression of human β-defensin 2 (hBD2), interleukin-8 (IL-8), villin, MD2, and Toll-like receptor 4 (TLR4).

RESULTS

Fecal hBD1 concentrations were consistently low in all patients, whereas hBD2 concentrations were high in meconium, particularly in clinical chorioamnionitis, and then dropped, followed by a steady increase after day 14. Infants with moderate NEC showed significantly increased fecal hBD2 concentrations before clinical symptoms, in contrast to infants developing severe NEC. Analysis of intestinal resection material obtained from patients with severe NEC revealed low hBD2 mRNA and protein levels, and increased expression of the inflammatory cytokine IL-8.

CONCLUSION

High hBD2 concentrations, reflecting strong intestinal immune responses, were associated with moderate courses of the disease. In severe NEC, low hBD2 expression was accompanied by low TLR4/MD2 expression, suggesting an inadequate response to luminal bacteria, possibly predisposing those infants to the development of NEC.

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.

Prophylactic probiotics to prevent death and nosocomial infection in preterm infants

BACKGROUND AND OBJECTIVE

It has been suggested that probiotics may decrease infant mortality and nosocomial infections because of their ability to suppress colonization and translocation of bacterial pathogens in the gastrointestinal tract. We designed a large double-blinded placebo-controlled trial using Lactobacillus reuteri to test this hypothesis in preterm infants.

METHODS

Eligible infants were randomly assigned during the first 48 hours of life to either daily probiotic administration or placebo. Infants in the intervention group were administered enterally 5 drops of a probiotic preparation containing 10(8) colony-forming units of L reuteri DSM 17938 until death or discharge from the NICU.

RESULTS

A total of 750 infants ≤ 2000 g were enrolled. The frequency of the primary outcome, death, or nosocomial infection, was similar in the probiotic and placebo groups (relative risk 0.87; 95% confidence interval: 0.63-1.19; P = .376). There was a trend toward a lower rate of nosocomial pneumonia in the probiotic group (2.4% vs 5.0%; P = .06) and a nonsignificant 40% decrease in necrotizing enterocolitis (2.4% vs 4.0%; P = .23). Episodes of feeding intolerance and duration of hospitalization were lower in infants ≤ 1500 g (9.6% vs 16.8% [P = .04]; 32.5 days vs 37 days [P = .03]).

CONCLUSIONS

Although L reuteri did not appear to decrease the rate of the composite outcome, the trends suggest a protective role consistent with what has been observed in the literature. Feeding intolerance and duration of hospitalization were decreased in premature infants ≤ 1500 g.

Probiotics and necrotizing enterocolitis: finding the missing pieces of the probiotic puzzle

Necrotizing enterocolitis (NEC) is one of the leading causes of death in the neonatal intensive care unit. Morbidity and mortality rates significantly increase with decreases in gestational age and birth weight. Strong evidence suggests probiotic prophylaxis may significantly decrease the incidence of NEC and should therefore be incorporated into the standard of care for preterm infants. However, debate still remains because of limitations of completed studies. The purpose of this review was to provide an overview of the controversies regarding probiotic use in preterm infants and to shed light on the practical considerations for implementation of probiotic supplementation.

Quantitative and qualitative study of intestinal flora in neonates

BACKGROUND

In the neonatal period the developing intestinal barrier function provides a sub-optimal mucosal defense against infection. Establishment of the normal commensal micro-flora plays a vital role in this process.

AIMS

To determine aerobic and anaerobic bacteria by quantitative and qualitative methods from faecal samples of neonates.

SETTINGS AND DESIGN

A prospective study was carried out in two groups in a tertiary care hospital, Group A-comprised preterm infant and in group B-full term infants.

MATERIALS AND METHODS

Sixty two preterm infants with the weight < 1500 gm and gestation age < 34 weeks and twenty nine full term infants with 4 weeks of age were included. Quantitation of bacterial load was done by ten-fold serial dilutions on respective media.

STATISTICAL ANALYSIS

The data were analyzed by using EPIINFO-Ver 6.04.

RESULTS AND CONCLUSIONS

The predominant aerobic bacterium was Klebsiella pneumoniae. In pre term infants aerobic bacteria were colonized with an average of 2.1 and anaerobic bacteria 0.1. Quantitation showed faecal bacterial colony count ranging from 10(4)-10(13) CFU/gms. Gram negative and gram positive bacteria increased gradually over an interval of 2 to 3 weeks. Mean log CFU of gram negative bacteria and gram positive bacteria were statistically insignificant from day 3 to day 14 (P > 0.05). On day 21 there was a significant change in colonization of both bacterial sp (P < 0.05). Potential pathogenic aerobic bacteria dominate the intestinal flora of premature babies nursed in neonatal unit. There is a need to investigate interventions to offset this imbalance in gut micro-ecology of premature babies.

Necrotizing enterocolitis in very low birth weight infants: a systemic review

Necrotizing enterocolitis (NEC) is the most common serious gastrointestinal disorder affecting very preterm or very low birth weight infants. The risk is inversely proportional to gestational age and weight at birth. Fetal growth restriction and compromise may be additional specific risk factors. Despite extensive research and animal studies etiopathogenesis, preventive strategies and management options remain controversial. The present paper reviews the literature for recent advances and newer insights for changing epidemiological trends, pathogenesis, role of inflammatory cytokines, and various preventive and management strategies.

Probiotics in neonatology

Probiotics are micro-organisms that confer health benefits on the host. Postulated mechanisms include: increasing resistance of the mucosal barrier to migration of bacteria and their toxins by strengthening intestinal cell junctions, modification of host response to microbial products, augmentation of immunoglobulin A mucosal responses, enhancement of enteral nutrition to inhibit the growth of pathogens; production of antimicrobial proteins; and competitive exclusion of potential pathogens. Published meta-analyses and systematic reviews report the effects of probiotics on important clinical outcomes in neonates. This paper will review the evidence for probiotic supplementation in neonatology, with a focus on preterm infants.

Necrotizing enterocolitis: old problem with new hope

The incidence of necrotizing enterocolitis (NEC) and mortality rate associated with this disease are not decreasing despite more than three decades of intensive research investigation and advances in neonatal intensive care. Although the etiology of NEC is not clearly elucidated, the most accepted hypothesis at present is that enteral feeding in the presence of intestinal hypoxia-ischemia-reperfusion, and colonization with pathogens provokes an inappropriately accentuated inflammatory response by the immature intestinal epithelial cells of the preterm neonate. However, delayed colonization of commensal flora with dysbiotic flora with a predominance of pathologic microorganisms plays a fundamental role in the pathogenesis of NEC. Recent studies have further identified that NEC infants have less diverse flora compared to age-matched controls without NEC. Increased gastric residual volume may be an early sign of NEC. An absolute neutrophil count of <1.5 × 10(9)/L and platelets below 100 × 10(9)/L are associated with an increased risk for mortality and gastrointestinal morbidity. Nonspecific supportive medical management should be initiated promptly. Sudden changes in vital signs such as tachycardia or impending shock may indicate perforation. A recent meta-analysis investigating using probiotics for prevention of NEC with a total of 2176 preterm very low birth weight infants found a success rate of just 1/25. Careful monitoring of the residual volume, and of serious changes in hemograms and vital signs may help in early diagnosis and prediction of when to perform medical or early surgical intervention. In term of prevention, administration of oral probiotics containing Bifidobacterium and Lactobacillus is a simple and safe method that attempts to early establish of commensal flora balance to inhibit pathogenic flora and an inflammatory response.

Enterocolite necrosante em recém-nascidos de muito baixo peso em uma unidade neonatal de alto risco do Nordeste do Brasil (2003-2007)

OBJETIVOS: avaliar a incidência de enterocolite necrosante (ECN), no período de 2003 a 2007, em crianças nascidas com muito baixo peso e descrever as características da assistência prestada a esses recém-nascidos. MÉTODOS: estudo longitudinal retrospectivo conduzido em uma unidade neonatal de alto risco com uma amostra de 1028 recém-nascidos de muito baixo peso, excluindo-se os menores de 750 g. A frequência de ECN foi observada do primeiro até o trigésimo dia de vida, ou até a sua ocorrência ou óbito, considerando-se o que ocorresse primeiro em um período de cinco anos. ECN foi definida pelo critério de Bell (estágio ≥2). Utilizou-se o qui-quadrado de tendência para avaliar o comportamento das variáveis categóricas ao longo dos cinco anos. RESULTADOS: ECN ocorreu em 55 dos 1028 recém-nascidos (5,3%). Observou-se maior incidência de ECN no ano de 2005 (19/204) com uma significante redução no ano de 2007 (8/195), entretanto, essa variação não caracterizou uma tendência (p=0,45). Observou-se aumento significante do uso de antibióticos,de nutrição parenteral, de corticóide antenatal e do consumo de leite materno e uma redução na média da idade gestacional de 2,4 semanas entre 2003 e 2007. CONCLUSÕES: a incidência de ECN foi variável, sem tendência de ascensão ou queda. Observou-se um incremento na cobertura de corticoide antenatal, aumento na utilização de leite materno e redução no consumo de fórmula. Mais estudos são necessários para melhor avaliar a contribuição dessas medidas na não progressão da incidência da ECN, apesar de tratar-se de uma população com risco elevado para essa doença.

Methionine requirement of the enterally fed term infant in the first month of life in the presence of cysteine

BACKGROUND

The essential amino acid methionine can be used for protein synthesis but also serves as a precursor for homocysteine and cysteine.

OBJECTIVE

The objective of this study was to determine the minimal obligatory methionine requirement of infants in the presence of excess cysteine (91 mg ⋅ kg(-1) ⋅ d(-1)) by using the indicator amino acid oxidation (IAAO) method with l-[1-(13)C]phenylalanine as the indicator.

DESIGN

Fully enterally fed term infants <1 mo of age were randomly assigned to methionine intakes that ranged from 3 to 59 mg ⋅ kg(-1) ⋅ d(-1) as part of an elemental formula. After 1 d of adaptation to the test diet, [(13)C]bicarbonate and l-[1-(13)C]phenylalanine tracers were given enterally. Breath samples were collected at baseline and during isotopic plateaus. The mean methionine requirement was determined by using biphasic linear regression crossover analysis on the fraction of (13)CO(2) recovery from l-[1-(13)C]phenylalanine oxidation (F(13)CO(2)). Data are presented as means ± SDs.

RESULTS

Thirty-three neonates (gestational age: 39 ± 1 wk) were studied at 13 ± 6 d. With increasing methionine intakes, F(13)CO(2) decreased until a methionine intake of 38 mg ⋅ kg(-1) ⋅ d(-1); additional increases in methionine intake did not affect F(13)CO(2). The mean methionine requirement was determined at 38 mg ⋅ kg(-1) ⋅ d(-1), and the upper and lower CIs were 48 and 27 mg ⋅ kg(-1) ⋅ d(-11), respectively (P < 0.0001, r(2) = 0.59).

CONCLUSIONS

Although the current recommended methionine intake of 28 mg ⋅ kg(-1) ⋅ d(-1) is within the CIs of our study, the estimated mean requirement is substantially higher. However, most of the infant formulas provide a methionine intake of 49-80 mg ⋅ kg(-1) ⋅ d(-1), which is above the upper CI of our study. This trial was registered at www.trialregister.nl as NTR1610.

Bacterial colonization and gut development in preterm neonates

Necrotizing enterocolitis (NEC) develops in 5-10% of preterm infants in association with enteral feeding and bacterial colonization. It remains unclear how diet and bacteria interact to protect or provoke the immature gastrointestinal tract. Understanding the factors that control bacterial colonization may provide the clue to prevent NEC, and studies in infants must be combined with animal models to understand the mechanisms of the microbiota-epithelium interactions. Analyses of infant fecal samples show that the density and distribution of bacterial species are highly variable with no consistent effects of gestational age, delivery mode, diet or probiotic administration, while low bacterial diversity and bacterial overgrowth are commonly associated with NEC. A series of recent studies in preterm pigs show that the mucosa-associated microbiota is affected by delivery method, prematurity and NEC progression and that diet has limited effects. Overgrowth of specific groups (e.g. Clostridia) appears to be a consequence of NEC, rather than the cause of NEC. Administration of probiotics either decreases or increases NEC sensitivity in preterm pigs, while in preterm infants probiotics have generally decreased NEC incidence and overall mortality. The optimal nature and amount of probiotic bacteria are unknown and host defense factors appear more important for NEC sensitivity than the nature of the gut microbiota. Host defense is improved by feeding the optimal amount of enteral diets, such as mother's colostrum or milk, that help the immature intestinal immune system to respond appropriately to the highly variable bacterial colonization.

Antibiotic use and misuse in the neonatal intensive care unit

Neonatal sepsis causes significant morbidity and mortality, especially in preterm infants. Clinicians are compelled to treat with empiric antibiotics at the first signs of suspected sepsis. Broad-spectrum antibiotics and prolonged treatment with empiric antibiotics are associated with adverse outcomes. Most common neonatal pathogens are susceptible to narrow-spectrum antibiotics. The choice of antibiotic and duration of empiric treatment are strongly associated with center-based risk factors. Clinicians should treat with short courses of narrow-spectrum antibiotics whenever possible, choosing the antibiotics and treatment duration to balance the risks of potentially untreated sepsis against the adverse effects of treatment in infants with sterile cultures.

Clostridia in premature neonates' gut: incidence, antibiotic susceptibility, and perinatal determinants influencing colonization

BACKGROUND

Although premature neonates (PN) gut microbiota has been studied, data about gut clostridial colonization in PN are scarce. Few studies have reported clostridia colonization in PN whereas Bacteroides and bifidobacteria have been seldom isolated. Such aberrant gut microbiota has been suggested to be a risk factor for the development of intestinal infections. Besides, PN are often treated by broad spectrum antibiotics, but little is known about how antibiotics can influence clostridial colonization based on their susceptibility patterns. The aim of this study was to report the distribution of Clostridium species isolated in feces from PN and to determine their antimicrobial susceptibility patterns. Additionally, clostridial colonization perinatal determinants were analyzed.

RESULTS

Of the 76 PN followed until hospital discharge in three French neonatal intensive care units (NICUs), 79% were colonized by clostridia. Clostridium sp. colonization, with a high diversity of species, increased throughout the hospitalization. Antibiotic courses had no effect on the clostridial colonization incidence although strains were found susceptible (except C. difficile) to anti-anaerobe molecules tested. However, levels of colonization were decreased by either antenatal or neonatal (during more than 10 days) antibiotic courses (p = 0.006 and p = 0.001, respectively). Besides, incidence of colonization was depending on the NICU (p = 0.048).

CONCLUSION

This study shows that clostridia are part of the PN gut microbiota. It provides for the first time information on the status of clostridia antimicrobial susceptibility in PN showing that strains were susceptible to most antibiotic molecules. Thus, the high prevalence of this genus is not linked to a high degree of resistance to antimicrobial agents or to the use of antibiotics in NICUs. The main perinatal determinant influencing PN clostridia colonization appears to be the NICU environment.

The early settlers: intestinal microbiology in early life

The human intestinal microbiota forms an integral part of normal human physiology, and disturbances of the normal gut microbiology have been implicated in many health and disease issues. Because newborns are essentially sterile, their microbiota must establish and develop from the very first days of life. The first colonizers play an important role in the development of the ecosystem and may impact the long-term composition and activity of the microbiota. These first settlers obviously develop and proliferate dependent on host characteristics and diet, but other factors can also significantly contribute to this vital biological process. Considering the importance of the microbiota for the human immune, metabolic, and neurological systems, it is important to understand the dynamics and driving determinants of this development. This review gives a global overview of our current understanding of the different factors impacting the intestinal microbiology in early life.

The effect of Lactobacillus rhamnosus GG supplemented enteral feeding on the microbiotic flora of preterm infants-double blinded randomized control trial

BACKGROUND AND AIM

Intestinal flora of preterms, dominantly presents with decreased amounts of physiological microbiota. This double blinded randomized control trial compared the stool of bottle fed preterms, randomized to receive lactobacillus rhamnosus GG (LGG) 6x109or placebo with formula feeding.

STUDY DESIGN

46 enterally fed preterms were randomized to receive probiotics or placebo within 0-3days after birth. All personnel were blinded to treatment assignment. Faecal sampling was preformed at day 7, 21, 42. Presence of LGG colonization, somatic growth and length of hospital stay were recorded.

RESULTS

60 patients were initially identified and enrolled but after exclusion criteria were applied, 21 babies were analyzed in the probiotic group and 26 in the placebo group. The number of lactobacillus were significantly higher (p=0.014) on day 7, and 21 (p=0.024) in the study group, and so was the number of enterobacteriaceae on all study days (p=0.004, p=0.000, p=0.000), and Enterococcus sp on day 21 (p=0.000). The amount of samples positive for staphylococci was significantly higher in the study group, on days 7 and 42 (p=0.001 and 0.011). We did not show a significant difference in weight gain upon discharge between the groups p=0.567, 95% CI (-168; 305) or mean of hospital stay p=0.421 95% CI (-13.43;5.71).

CONCLUSIONS

A preterm infant formula with an addition of probiotics leads to a rapid growth of LGG in the gut of bottle fed infants, but does not decrease the amount of pathogenic organisms, nor increase weight gain during enteral feeding, or decrease length of hospital stay.

Investigation of the early intestinal microflora in premature infants with/without necrotizing enterocolitis using two different methods

INTRODUCTION

The pathophysiology of necrotizing enterocolitis (NEC) is multifactorial, and gastrointestinal bacteria are thought to play an important role. In this study, the role of microflora in the gastrointestinal tract of neonates with NEC was assessed by comparing cases with controls.

RESULTS

Of the 163 neonates, 21 developed NEC. The risk of NEC decreased by 8% with each additional day of gestational age.

DISCUSSION

Typically, very few bacterial species could be cultured from the fecal specimens obtained. Gram-positive (G(+)) bacteria dominated the samples in the NEC group, whereas in the control group mixed flora of G(+) and Gram-negative (G(-)) bacteria were isolated. Surprisingly, molecular analysis using PCR-DGGE profiles did not confirm these differences. Our data suggest that G(+) bacteria in the intestine may play a role in the development of NEC in premature infants.

METHODS

One hundred and sixty three neonates born at <30 weeks of gestation were enrolled. Fecal samples taken during the first month of life were subjected to culture and PCR-denaturing gradient gel electrophoresis (PCR-DGGE). A total of 482 fecal samples were examined.

Beyond bacteria: a study of the enteric microbial consortium in extremely low birth weight infants

Extremely low birth weight (ELBW) infants have high morbidity and mortality, frequently due to invasive infections from bacteria, fungi, and viruses. The microbial communities present in the gastrointestinal tracts of preterm infants may serve as a reservoir for invasive organisms and remain poorly characterized. We used deep pyrosequencing to examine the gut-associated microbiome of 11 ELBW infants in the first postnatal month, with a first time determination of the eukaryote microbiota such as fungi and nematodes, including bacteria and viruses that have not been previously described. Among the fungi observed, Candida sp. and Clavispora sp. dominated the sequences, but a range of environmental molds were also observed. Surprisingly, seventy-one percent of the infant fecal samples tested contained ribosomal sequences corresponding to the parasitic organism Trichinella. Ribosomal DNA sequences for the roundworm symbiont Xenorhabdus accompanied these sequences in the infant with the greatest proportion of Trichinella sequences. When examining ribosomal DNA sequences in aggregate, Enterobacteriales, Pseudomonas, Staphylococcus, and Enterococcus were the most abundant bacterial taxa in a low diversity bacterial community (mean Shannon-Weaver Index of 1.02±0.69), with relatively little change within individual infants through time. To supplement the ribosomal sequence data, shotgun sequencing was performed on DNA from multiple displacement amplification (MDA) of total fecal genomic DNA from two infants. In addition to the organisms mentioned previously, the metagenome also revealed sequences for gram positive and gram negative bacteriophages, as well as human adenovirus C. Together, these data reveal surprising eukaryotic and viral microbial diversity in ELBW enteric microbiota dominated bytypes of bacteria known to cause invasive disease in these infants.

Probiotic bacteria induce maturation of intestinal claudin 3 expression and barrier function

An immature intestinal epithelial barrier may predispose infants and children to many intestinal inflammatory diseases, such as infectious enteritis, inflammatory bowel disease, and necrotizing enterocolitis. Understanding the factors that regulate gut barrier maturation may yield insight into strategies to prevent these intestinal diseases. The claudin family of tight junction proteins plays an important role in regulating epithelial paracellular permeability. Previous reports demonstrate that rodent intestinal barrier function matures during the first 3 weeks of life. We show that murine paracellular permeability markedly decreases during postnatal maturation, with the most significant change occurring between 2 and 3 weeks. Here we report for the first time that commensal bacterial colonization induces intestinal barrier function maturation by promoting claudin 3 expression. Neonatal mice raised on antibiotics or lacking the toll-like receptor adaptor protein MyD88 exhibit impaired barrier function and decreased claudin 3 expression. Furthermore, enteral administration of either live or heat-killed preparations of the probiotic Lactobacillus rhamnosus GG accelerates intestinal barrier maturation and induces claudin 3 expression. However, live Lactobacillus rhamnosus GG increases mortality. Taken together, these results support a vital role for intestinal flora in the maturation of intestinal barrier function. Probiotics may prevent intestinal inflammatory diseases by regulating intestinal tight junction protein expression and barrier function. The use of heat-killed probiotics may provide therapeutic benefit while minimizing adverse effects.

Lysine requirement of the enterally fed term infant in the first month of life

BACKGROUND

Infant nutrition has a major impact on child growth and functional development. Low and high intakes of protein or amino acids could have a detrimental effect.

OBJECTIVE

The objective of the study was to determine the lysine requirement of enterally fed term neonates by using the indicator amino acid oxidation (IAAO) method. L-[1-(13)C]phenylalanine was used as an indicator amino acid.

DESIGN

Twenty-one neonates were randomly assigned to lysine intakes that ranged from 15 to 240 mg · kg(-1) · d(-1). Breath, urine, and blood samples were collected at baseline and during the plateau. The mean lysine requirement was determined by using biphasic linear regression crossover analysis on the fraction of (13)CO(2) recovery from L-[1-(13)C]phenylalanine oxidation (F(13)CO(2)) and phenylalanine oxidation rates calculated from the L-[1-(13)C]phenylalanine enrichment of urine and plasma.

RESULTS

The mean (±SD) phenylalanine flux calculated from urine and plasma L-[1-(13)C]phenylalanine enrichment data were 88.3 ± 6.9 and 84.5 ± 7.4 μmol · kg(-1) · h(-1), respectively. Graded intakes of lysine had no effect on phenylalanine fluxes. The mean lysine requirement determined by F(13)CO(2) was 130 mg · kg(-1) · d(-1) (upper and lower CIs: 183.7 and 76.3 mg · kg(-1) · d(-1), respectively). The mean requirement was identical to the requirement determined by using phenylalanine oxidation rates in urine and plasma.

CONCLUSIONS

The mean lysine requirement of enterally fed term neonates was determined by using F(13)CO(2) and phenylalanine oxidation rates calculated from the L-[1-(13)C]phenylalanine enrichment of urine and plasma. These methods yielded a similar result of 130 mg lysine · kg(-1) · d(-1). This study demonstrates that sampling of (13)CO(2) in expired air is sufficient to estimate the lysine requirement by using the IAAO method in infants. This trial was registered at www.trialregister.nl as NTR1610.

Choice and duration of antimicrobial therapy for neonatal sepsis and meningitis

Neonatal sepsis is associated with increased mortality and morbidity including neurodevelopmental impairment and prolonged hospital stay. Signs and symptoms of sepsis are nonspecific, and empiric antimicrobial therapy is promptly initiated after obtaining appropriate cultures. However, many preterm and low birth weight infants who do not have infection receive antimicrobial agents during hospital stay. Prolonged and unnecessary use of antimicrobial agents is associated with deleterious effects on the host and the environment. Traditionally, the choice of antimicrobial agents is based on the local policy, and the duration of therapy is decided by the treating physician based on clinical symptoms and blood culture results. In this paper, we discuss briefly the causative organism of neonatal sepsis in both the developed and developing countries. We review the evidence for appropriate choice of empiric antimicrobial agents and optimal duration of therapy in neonates with suspected sepsis, culture-proven sepsis, and meningitis. Moreover, there is significant similarity between the causative organisms for early- and late-onset sepsis in developing countries. The choice of antibiotic described in this paper may be more applicable in developed countries.

Pyrosequencing-based molecular monitoring of the intestinal bacterial colonization in preterm infants

OBJECTIVES

The aim of the study was to investigate the previously unexplored diversity of neonatal intestinal microbiota and monitor early intestinal colonization patterns in Korean preterm infants using high-throughput pyrosequencing technology combined with 16S rDNA-based molecular methods.

SUBJECTS AND METHODS

A total of 46,369 partial 16S rDNA sequences obtained from 30 fecal samples serially taken from 10 very-low-birth weight preterm infants were analyzed.

RESULTS

A significant proportion of the molecular species (21.9%) was found to be unclassified. The pathogenic or potentially pathogenic molecular species belonging to the classes Gammaproteobacteria and Bacilli were predominant during the entire observation period. Anaerobic or nonpathogenic molecular species belonging to the class Clostridia (except Clostridium difficile) and phyla Bacteroidetes were ubiquitous even within 72 hours after birth. The proportion of these species increased significantly at 1 month of age. The most ubiquitous and abundant major molecular genera common to all of the postnatal ages were Escherichia, Enterobacter, Enterococcus, Veillonella, Serratia, Staphylococcus, Roseburia, Acinetobacter, Citrobacter, Bacteroides, Faecalibacterium, Blautia, and Streptococcus.

CONCLUSIONS

The diversity and dynamic nature of intestinal bacterial colonization in very-low-birth weight preterm infants were revealed using pyrosequencing technology. The results of the present pilot study may provide a basis to consider when investigating or interpreting the role of intestinal microbiota in certain preterm infant diseases such as necrotizing enterocolitis or systemic infection.

Antibiotic exposure in the newborn intensive care unit and the risk of necrotizing enterocolitis

OBJECTIVE

To determine whether duration of antibiotic exposure is an independent risk factor for necrotizing enterocolitis (NEC).

STUDY DESIGN

A retrospective, 2:1 control-case analysis was conducted comparing neonates with NEC to those without from 2000 through 2008. Control subjects were matched on gestational age, birth weight, and birth year. In each matched triad, demographic and risk factor data were collected from birth until the diagnosis of NEC in the case subject. Bivariate and multivariate analyses were used to assess associations between risk factors and NEC.

RESULTS

One hundred twenty-four cases of NEC were matched with 248 control subjects. Cases were less likely to have respiratory distress syndrome (P = .018) and more likely to reach full enteral feeding (P = .028) than control subjects. Cases were more likely to have culture-proven sepsis (P < .0001). Given the association between sepsis and antibiotic use, we tested for and found a significant interaction between the two variables (P = .001). When neonates with sepsis were removed from the cohort, the risk of NEC increased significantly with duration of antibiotic exposure. Exposure for >10 days resulted in a nearly threefold increase in the risk of developing NEC.

CONCLUSIONS

Duration of antibiotic exposure is associated with an increased risk of NEC among neonates without prior sepsis.

The ProPrems trial: investigating the effects of probiotics on late onset sepsis in very preterm infants

Background

Late onset sepsis is a frequent complication of prematurity associated with increased mortality and morbidity. The commensal bacteria of the gastrointestinal tract play a key role in the development of healthy immune responses. Healthy term infants acquire these commensal organisms rapidly after birth. However, colonisation in preterm infants is adversely affected by delivery mode, antibiotic treatment and the intensive care environment. Altered microbiota composition may lead to increased colonisation with pathogenic bacteria, poor immune development and susceptibility to sepsis in the preterm infant.

Probiotics are live microorganisms, which when administered in adequate amounts confer health benefits on the host. Amongst numerous bacteriocidal and nutritional roles, they may also favourably modulate host immune responses in local and remote tissues. Meta-analyses of probiotic supplementation in preterm infants report a reduction in mortality and necrotising enterocolitis. Studies with sepsis as an outcome have reported mixed results to date.

Allergic diseases are increasing in incidence in "westernised" countries. There is evidence that probiotics may reduce the incidence of these diseases by altering the intestinal microbiota to influence immune function.

Methods/Design

This is a multi-centre, randomised, double blinded, placebo controlled trial investigating supplementing preterm infants born at < 32 weeks' gestation weighing < 1500 g, with a probiotic combination (Bifidobacterium infantis, Streptococcus thermophilus and Bifidobacterium lactis). A total of 1,100 subjects are being recruited in Australia and New Zealand. Infants commence the allocated intervention from soon after the start of feeds until discharge home or term corrected age. The primary outcome is the incidence of at least one episode of definite (blood culture positive) late onset sepsis before 40 weeks corrected age or discharge home. Secondary outcomes include: Necrotising enterocolitis, mortality, antibiotic usage, time to establish full enteral feeds, duration of hospital stay, growth measurements at 6 and 12 months' corrected age and evidence of atopic conditions at 12 months' corrected age.

Discussion

Results from previous studies on the use of probiotics to prevent diseases in preterm infants are promising. However, a large clinical trial is required to address outstanding issues regarding safety and efficacy in this vulnerable population. This study will address these important issues.

Trial registration

Australia and New Zealand Clinical Trials Register (ANZCTR): ACTRN012607000144415

The product "ABC Dophilus Probiotic Powder for Infants^®", Solgar, USA has its 3 probiotics strains registered with the Deutsche Sammlung von Mikroorganismen und Zellkulturen (DSMZ - German Collection of Microorganisms and Cell Cultures) as BB-12 15954, B-02 96579, Th-4 15957.

Evidence-based guidelines for use of probiotics in preterm neonates

BACKGROUND

Current evidence indicates that probiotic supplementation significantly reduces all-cause mortality and definite necrotising enterocolitis without significant adverse effects in preterm neonates. As the debate about the pros and cons of routine probiotic supplementation continues, many institutions are satisfied with the current evidence and wish to use probiotics routinely. Because of the lack of detail on many practical aspects of probiotic supplementation, clinician-friendly guidelines are urgently needed to optimise use of probiotics in preterm neonates.

AIM

To develop evidence-based guidelines for probiotic supplementation in preterm neonates.

METHODS

To develop core guidelines on use of probiotics, including strain selection, dose and duration of supplementation, we primarily used the data from our recent updated systematic review of randomised controlled trials. For equally important issues including strain identification, monitoring for adverse effects, product format, storage and transport, and regulatory hurdles, a comprehensive literature search, covering the period 1966-2010 without restriction on the study design, was conducted, using the databases PubMed and EMBASE, and the proceedings of scientific conferences; these data were used in our updated systematic review.

RESULTS

In this review, we present guidelines, including level of evidence, for the practical aspects (for example, strain selection, dose, duration, clinical and laboratory surveillance) of probiotic supplementation, and for dealing with non-clinical but important issues (for example, regulatory requirements, product format). Evidence was inadequate in some areas, and these should be a target for further research.

CONCLUSION

We hope that these evidence-based guidelines will help to optimise the use of probiotics in preterm neonates. Continued research is essential to provide answers to the current gaps in knowledge about probiotics.

Risk factors associated with gut and nasopharyngeal colonization by common Gram-negative species and yeasts in neonatal intensive care units patients

AIM

To characterize dynamics of mucosal colonization of neonates by common aerobic Gram negative species and Candida spp. and to identify independent perinatal, neonatal, and environmental factors influencing the colonization process.

STUDY DESIGN

The nasopharyngeal (n=1145) and rectal (n=1242) swabs were collected on admission and thereafter twice a week in neonates with risk factors of early onset sepsis (n=276) admitted within the first 72 h of life. The association between colonization by different microbes and a total of 22 predefined risk factors was assessed using univariate and multiple logistic regression analyses.

RESULTS

Throughout the study about half of the patients had rectal (55.8%) or nasopharyngeal colonization (42.8%) with common Gram-negative microorganisms. Colonization dynamics and risk factors were in general similar for a given bacterial species in both mucosal sites; nonfermentative microbes more often found in nasopharyngeal swabs and Enterobacteriaceae in rectal swabs. All organisms except Escherichia coli were influenced by the duration of intensive care unit stay but other risk factors were species specific, perhaps reflecting their mode of acquisition. While colonization by E. coli and Candida albicans was associated with perinatal factors like term birth, vaginal delivery, and breast milk feeding; colonization by Klebsiella pneumoniae, Enteribacter cloacae, Acinetobacter spp. and non-albicans Candida spp. were mostly determined by hospital environment (treatment unit and period, artificial interventions and their duration) and gestation age ≤ 28 weeks.

CONCLUSIONS

The knowledge of risk factor profiles may permit the development of strategies to prevent heavy colonization and subsequent invasive disease in high risk infants.

Community analysis of bacteria colonizing intestinal tissue of neonates with necrotizing enterocolitis

BACKGROUND

Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency in newborn neonates. Bacteria are believed to be important in the pathogenesis of NEC but bacterial characterization has only been done on human faecal samples and experimental animal studies. The aim of this study was to investigate the microbial composition and the relative number of bacteria in inflamed intestinal tissue surgically removed from neonates diagnosed with NEC (n=24). The bacterial populations in the specimens were characterized by laser capture microdissection and subsequent sequencing combined with fluorescent in situ hybridization (FISH), using bacterial rRNA-targeting oligonucleotide probes.

RESULTS

Bacteria were detected in 22 of the 24 specimens, 71% had moderate to high densities of bacteria. The phyla detected by 16S rRNA gene sequencing were: Proteobacteria (49.0%), Firmicutes (30.4%), Actinobacteria (17.1%) and Bacteroidetes (3.6%). A major detected class of the phylum Proteobacteria belonged to δ-proteobacteria. Surprisingly, Clostridium species were only detected in 4 of the specimens by FISH, but two of these specimens exhibited histological pneumatosis intestinalis and both specimens had a moderate to a high density of C. butyricum and C. parputrificum detected by using species specific FISH probes. A 16S rRNA gene sequence tag similar to Ralstonia species was detected in most of the neonatal tissues and members of this genus have been reported to be opportunistic pathogens but their role in NEC has still to be clarified.

CONCLUSION

In this study, in situ identification and community analysis of bacteria found in tissue specimens from neonates with NEC, were analysed for the first time. Although a large variability of bacteria was found in most of the analyzed specimens, no single or combination of known potential pathogenic bacteria species was dominating the samples suggestive NEC as non-infectious syndrome. However there was a significant correlation between the presence of C. butyricum & C. parputrificum and histological pneumatosis intestinalis. Finally this study emphasizes the possibility to examine the microbial composition directly on excised human tissues to avoid biases from faecal samples or culturing.

Microbiome aspects of perinatal and neonatal health

Our human cells are outnumbered 10 to 1 by bacterial cells. For this reason, the role of microorganisms, specifically bacteria, in health and disease has brought forth intense research via the Human Microbiome Project. The Human Microbiome Project is a National Institutes of Health sponsored effort to build upon the Human Genome Project in understanding human genetic and physiologic diversity. Perinatal and neonatal health represents areas of high importance for knowledge generated by the Human Microbiome Project as the microbiome is largely influenced during pregnancy, birth, and the neonatal period by nutrition, lifestyle, environmental factors of care, and the administration of medications, specifically antibiotics. As nurses have a depth of expertise in these areas, they will make a significant contribution toward better understanding the role of the microbiome in disease, and how to manipulate the microbiome to advantage patients toward health. This article describes the human microbiome and why it is important to overall health and disease. Three major unsolved problems in perinatal and neonatal health including (1) preterm birth; (2) the neonatal consequences of vaginal versus cesarean birth; and (3) neonatal gastrointestinal disease, specifically, necrotizing enterocolitis, are discussed in the context of current and future research on the human microbiome.

A fermented formula in pre-term infants: clinical tolerance, gut microbiota, down-regulation of faecal calprotectin and up-regulation of faecal secretory IgA

Intestinal bacterial colonisation in pre-term infants is delayed compared with full-term infants, leading to an increased risk of gastrointestinal disease. Modulation of colonisation through dietary supplementation with probiotics or prebiotics could decrease such a risk. The present study evaluated clinical tolerance, the effects on gut microbiota, and inflammatory and immunological mucosal responses to an infant formula adapted for pre-term infants that included in its manufacturing process a fermentation step with two probiotic strains, Bifidobacterium breve C50 and Streptococcus thermophilus 065, inactivated by heat at the end of the process. A total of fifty-eight infants (gestational age: 30–35 weeks), fed either the fermented pre-term formula or a standard pre-term formula, were followed up during their hospital stay. Clinical tolerance, faecal microbiota using a culture and a culture-independent method (temporal temperature gel electrophoresis), faecal calprotectin and secretory IgA were analysed weekly. No difference was observed regarding anthropometric data and digestive tolerance, except for abdominal distension, the incidence of which was lower in infants fed the fermented formula for 2 weeks. Bacterial colonisation was not modified by the type of feeding, particularly for bifidobacteria. Faecal calprotectin was significantly lower in infants fed the fermented formula for 2 weeks, and secretory IgA increased with both mother's milk and the fermented formula. The fermented formula was well tolerated and did not significantly modulate the bacterial colonisation but had benefits on inflammatory and immune markers, which might be related to some features of gastrointestinal tolerance.

Probiotics for prevention of necrotizing enterocolitis in preterm infants

BACKGROUND

Necrotizing enterocolitis (NEC) and nosocomial sepsis are associated with increased morbidity and mortality in preterm infants. Through prevention of bacterial migration across the mucosa, competitive exclusion of pathogenic bacteria, and enhancing the immune responses of the host, prophylactic enteral probiotics (live microbial supplements) may play a role in reducing NEC and associated morbidity.

OBJECTIVES

To compare the efficacy and safety of prophylactic enteral probiotics administration versus placebo or no treatment in the prevention of severe NEC and/or sepsis in preterm infants.

SEARCH STRATEGY

For this update, searches were made of MEDLINE (1966 to October 2010), EMBASE (1980 to October 2010), the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2010), and abstracts of annual meetings of the Society for Pediatric Research (1995 to 2010).

SELECTION CRITERIA

Only randomized or quasi-randomized controlled trials that enrolled preterm infants < 37 weeks gestational age and/or < 2500 g birth weight were considered. Trials were included if they involved enteral administration of any live microbial supplement (probiotics) and measured at least one prespecified clinical outcome.

DATA COLLECTION AND ANALYSIS

Standard methods of the Cochrane Collaboration and its Neonatal Group were used to assess the methodologic quality of the trials, data collection and analysis.

MAIN RESULTS

Sixteen eligible trials randomizing 2842 infants were included. Included trials were highly variable with regard to enrollment criteria (i.e. birth weight and gestational age), baseline risk of NEC in the control groups, timing, dose, formulation of the probiotics, and feeding regimens. Data regarding extremely low birth weight infants (ELBW) could not be extrapolated. In a meta-analysis of trial data, enteral probiotics supplementation significantly reduced the incidence of severe NEC (stage II or more) (typical RR 0.35, 95% CI 0.24 to 0.52) and mortality (typical RR 0.40, 95% CI 0.27 to 0.60). There was no evidence of significant reduction of nosocomial sepsis (typical RR 0.90, 95% CI 0.76 to 1.07). The included trials reported no systemic infection with the probiotics supplemental organism. The statistical test of heterogeneity for NEC, mortality and sepsis was insignificant.

AUTHORS' CONCLUSIONS

Enteral supplementation of probiotics prevents severe NEC and all cause mortality in preterm infants. Our updated review of available evidence supports a change in practice. More studies are needed to assess efficacy in ELBW infants and assess the most effective formulation and dose to be utilized.

Dynamics and clinical evolution of bacterial gut microflora in extremely premature patients

OBJECTIVE

To determine baseline clinical characteristics that influence bacterial gut flora dynamics in very preterm infants and the relationship between gut flora dynamics and clinical evolution.

STUDY DESIGN

Prospective, monocentric study enrolling 29 consecutive very preterm infants. We collected data about growth, digestive tolerance, nutrition, and antibiotic use. Microflora in stool samples, collected between 3 and 56 days of life, was identified with direct molecular fingerprinting.

RESULTS

Median (interquartile range) body weight and gestational age at birth were 950 g (760-1060 g) and 27 weeks (27-29 weeks), respectively. The diversity score (number of operational taxonomic units) increased 0.45 units/week (P < .0001), with staphylococci as the major group. Bifidobacterium was poorly represented. Gestational age (≥ 28 weeks) and caesarean delivery independently correlated with better diversity scores during follow-up (P < .05). The 6-week diversity score inversely correlated with the duration of antibiotherapy (P = .0184) and parenteral feeding (P = .013). The microflora dynamics was associated with the digestive tolerance profile. Weight gain increased with increasing diversity score (P = .0428).

CONCLUSION

Microflora diversity settled progressively in very preterm infants. Staphylococci were the major group, and few infants were colonized with Bifidobacterium spp. Measures that may improve microflora could have beneficial effects on digestive tolerance and growth.

Strain-resolved community genomic analysis of gut microbial colonization in a premature infant

The intestinal microbiome is a critical determinant of human health. Alterations in its composition have been correlated with chronic disorders, such as obesity and inflammatory bowel disease in adults, and may be associated with neonatal necrotizing enterocolitis in premature infants. Increasing evidence suggests that strain-level genomic variation may underpin distinct ecological trajectories within mixed populations, yet there have been few strain-resolved analyses of genotype-phenotype connections in the context of the human ecosystem. Here, we document strain-level genomic divergence during the first 3 wk of life within the fecal microbiota of an infant born at 28-wk gestation. We observed three compositional phases during colonization, and reconstructed and intensively curated population genomic datasets from the third phase. The relative abundance of two Citrobacter strains sharing ~99% nucleotide identity changed significantly over time within a community dominated by a nearly clonal Serratia population and harboring a lower abundance Enterococcus population and multiple plasmids and bacteriophage. Modeling of Citrobacter strain abundance suggests differences in growth rates and host colonization patterns. We identified genotypic variation potentially responsible for divergent strain ecologies, including hotspots of sequence variation in regulatory genes and intergenic regions, and in genes involved in transport, flagellar biosynthesis, substrate metabolism, and host colonization, as well as differences in the complements of these genes. Our results demonstrate that a community genomic approach can elucidate gut microbial colonization at the resolution required to discern medically relevant strain and species population dynamics, and hence improve our ability to diagnose and treat microbial community-mediated disorders.

Role of probiotics in the prevention of the enteric colonization by Candida in preterm newborns: incidence of late-onset sepsis and neurological outcome

OBJECTIVE

To evaluate the efficacy of probiotics in the prevention of gastrointestinal colonization by Candida species, of late-onset sepsis and neurological outcome in preterm newborns.

STUDY DESIGN

A prospective study was conducted in 249 preterms who were subdivided into three groups: one group (n=83) was supplemented with Lactobacillus (L.) reuteri, one group with L. rhamnosus (n=83) and the other with no supplementation (n=83). The fungal colonization in the gastrointestinal tract, the late onset of sepsis and clinical parameters were recorded. A neurological structured assessment was further performed at 1 year of age.

RESULT

Candida stool colonization was significantly higher (P<0.01) in the control group than in the groups treated with probiotics. The L. reuteri group presented a significantly higher reduction in gastrointestinal symptoms than did the L. rhamnosus and control groups. Infants treated with probiotics showed a statistically significant lower incidence of abnormal neurological outcome than did the control group.

CONCLUSION

The use of both probiotics seems to be effective in the prevention of gastrointestinal colonization by Candida, in the protection from late-onset sepis and in reducing abnormal neurological outcomes in preterms.

Nutritional modulation of the gut microbiota and immune system in preterm neonates susceptible to necrotizing enterocolitis

The gastrointestinal inflammatory disorder, necrotizing enterocolitis (NEC), is among the most serious diseases for preterm neonates. Nutritional, microbiological and immunological dysfunctions all play a role in disease progression but the relationship among these determinants is not understood. The preterm gut is very sensitive to enteral feeding which may either promote gut adaptation and health, or induce gut dysfunction, bacterial overgrowth and inflammation. Uncontrolled inflammatory reactions may be initiated by maldigestion and impaired mucosal protection, leading to bacterial overgrowth and excessive nutrient fermentation. Tumor necrosis factor alpha, toll-like receptors and heat-shock proteins are identified among the immunological components of the early mucosal dysfunction. It remains difficult, however, to distinguish the early initiators of NEC from the later consequences of the disease pathology. To elucidate the mechanisms and identify clinical interventions, animal models showing spontaneous NEC development after preterm birth coupled with different forms of feeding may help. In this review, we summarize the literature and some recent results from studies on preterm pigs on the nutritional, microbial and immunological interactions during the early feeding-induced mucosal dysfunction and later NEC development. We show that introduction of suboptimal enteral formula diets, coupled with parenteral nutrition, predispose to disease, while advancing amounts of mother's milk from birth (particularly colostrum) protects against disease. Hence, the transition from parenteral to enteral nutrition shortly after birth plays a pivotal role to secure gut growth, digestive maturation and an appropriate response to bacterial colonization in the sensitive gut of preterm neonates.

Probiotics and prebiotics in pediatrics

This clinical report reviews the currently known health benefits of probiotic and prebiotic products, including those added to commercially available infant formula and other food products for use in children. Probiotics are supplements or foods that contain viable microorganisms that cause alterations of the microflora of the host. Use of probiotics has been shown to be modestly effective in randomized clinical trials (RCTs) in (1) treating acute viral gastroenteritis in healthy children; and (2) preventing antibiotic-associated diarrhea in healthy children. There is some evidence that probiotics prevent necrotizing enterocolitis in very low birth weight infants (birth weight between 1000 and 1500 g), but more studies are needed. The results of RCTs in which probiotics were used to treat childhood Helicobacter pylori gastritis, irritable bowel syndrome, chronic ulcerative colitis, and infantile colic, as well as in preventing childhood atopy, although encouraging, are preliminary and require further confirmation. Probiotics have not been proven to be beneficial in treating or preventing human cancers or in treating children with Crohn disease. There are also safety concerns with the use of probiotics in infants and children who are immunocompromised, chronically debilitated, or seriously ill with indwelling medical devices. Prebiotics are supplements or foods that contain a nondigestible food ingredient that selectively stimulates the favorable growth and/or activity of indigenous probiotic bacteria. Human milk contains substantial quantities of prebiotics. There is a paucity of RCTs examining prebiotics in children, although there may be some long-term benefit of prebiotics for the prevention of atopic eczema and common infections in healthy infants. Confirmatory well-designed clinical research studies are necessary.

Bifidobacterium bifidum reduces apoptosis in the intestinal epithelium in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating intestinal disease of neonates, and clinical studies suggest the beneficial effect of probiotics in NEC prevention. Recently, we have shown that administration of Bifidobacterium bifidum protects against NEC in a rat model. Intestinal apoptosis can be suppressed by activation of cyclooxygenase-2 (COX-2) and increased production of prostaglandin E(2) (PGE(2)). The present study investigates the effect of B. bifidum on intestinal apoptosis in the rat NEC model and in an intestinal epithelial cell line (IEC-6), as a mechanism of protection against mucosal injury. Premature rats were divided into the following three groups: dam fed, hand fed with formula (NEC), or hand fed with formula supplemented with B. bifidum (NEC + B. bifidum). Intestinal Toll-like receptor-2 (TLR-2), COX-2, PGE(2), and apoptotic regulators were measured. The effect of B. bifidum was verified in IEC-6 cells using a model of cytokine-induced apoptosis. Administration of B. bifidum increased expression of TLR-2, COX-2, and PGE(2) and significantly reduced apoptosis in the intestinal epithelium of both in vivo and in vitro models. The Bax-to-Bcl-w ratio was shifted toward cell survival, and the number of cleaved caspase-3 positive cells was markedly decreased in B. bifidum-treated rats. Experiments in IEC-6 cells showed anti-apoptotic effect of B. bifidum. Inhibition of COX-2 signaling blocked the protective effect of B. bifidum treatment in both in vivo and in vitro models. In conclusion, oral administration of B. bifidum activates TLR-2 in the intestinal epithelium. B. bifidum increases expression of COX-2, which leads to higher production of PGE(2) in the ileum and protects against intestinal apoptosis associated with NEC. This study indicates the ability of B. bifidum to downregulate apoptosis in the rat NEC model and in IEC-6 cells by a COX-2-dependent matter and suggests a molecular mechanism by which this probiotic reduces mucosal injury and preserves intestinal integrity.

Parenteral antibiotics reduce bifidobacteria colonization and diversity in neonates

We investigated the impact of parenteral antibiotic treatment in the early neonatal period on the evolution of bifidobacteria in the newborn. Nine babies treated with intravenous ampicillin/gentamicin in the first week of life and nine controls (no antibiotic treatment) were studied. Denaturing gradient gel electrophoresis was used to investigate the composition of Bifidobacterium in stool samples taken at four and eight weeks. Bifidobacteria were detected in all control infants at both four and eight weeks, while only six of nine antibiotic-treated infants had detectable bifidobacteria at four weeks and eight of nine at eight weeks. Moreover, stool samples of controls showed greater diversity of Bifidobacterium spp. compared with antibiotic-treated infants. In conclusion, short-term parenteral antibiotic treatment of neonates causes a disturbance in the expected colonization pattern of bifidobacteria in the first months of life. Further studies are required to probiotic determine if supplementation is necessary in this patient group.