Reduced enterobacterial and increased staphylococcal colonization of the infantile bowel: an effect of hygienic lifestyle?

Bloodstream infections in very low birth weight infants with intestinal failure

OBJECTIVE

To examine pathogens and other characteristics associated with late-onset bloodstream infections (BSIs) in infants with intestinal failure (IF) as a consequence of necrotizing enterocolitis (NEC).

STUDY DESIGN

Infants weighing 401-1500 g at birth who survived for >72 hours and received care at Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network centers were studied. The frequency of culture-positive BSI and pathogens were compared in infants with medically managed NEC, NEC managed surgically without IF, and surgical IF. Among infants with IF, the duration of parenteral nutrition (PN) and other outcomes were evaluated.

RESULTS

A total of 932 infants were studied (IF, n = 78; surgical NEC without IF, n = 452; medical NEC, n = 402). The proportion with BSI after diagnosis of NEC was higher in the infants with IF than in those with surgical NEC (P = .007) or medical NEC (P < .001). Gram-positive pathogens were most frequent. Among infants with IF, an increased number of infections was associated with longer hospitalization and duration of PN (median stay: 172 for those with 0 infections, 188 days for those with 1 infection, and 260 days for those with ≥2 infections [P = .06]; median duration of PN: 90, 112, and 115 days, respectively [P = .003]) and decreased achievement of full feeds during hospitalization (87%, 67%, and 50%, respectively; P = .03).

CONCLUSION

Recurrent BSIs are common in very low birth weight infants with IF. Gram-positive bacteria were the most commonly identified organisms in these infants.

Establishment of the bacterial fecal community during the first month of life in Brazilian newborns

OBJECTIVE

The establishment of the intestinal microbiota in newborns is a critical period with possible long-term consequences for human health. In this research, the development of the fecal microbiota of a group of exclusively breastfed neonates living in low socio-economic conditions in the city of São Paulo, Brazil, during the first month of life, was studied.

METHODS

Fecal samples were collected from ten neonates on the second, seventh, and 30(th) days after birth. One of the neonates underwent antibiotic therapy. Molecular techniques were used for analysis; DNA was extracted from the samples, and 16S rRNA libraries were sequenced and phylogenetically analyzed after construction. A real-time polymerase chain reaction (PCR) was performed on the samples taken from the 30(th) day to amplify DNA from Bifidobacterium sp.

RESULTS

The primary phylogenetic groups identified in the samples were Escherichia and Clostridium. Staphylococcus was identified at a low rate. Bifidobacterium sp. was detected in all of the samples collected on the 30(th) day. In the child who received antibiotics, a reduction in anaerobes and Escherichia, which was associated with an overgrowth of Klebsiella, was observed throughout the experimental period.

CONCLUSION

The observed pattern of Escherichia predominance and reduced Staphylococcus colonization is in contrast with the patterns observed in neonates living in developed countries.

Current technology in the diagnosis of developmentally related lung disorders

Respiratory disorders that present in the newborn period may result from structural, functional, or acquired mechanisms that limit gas exchange between the airspace and vascular bed. Exciting new imaging, gene sequencing, mass spectrometry, and molecular and cell-based techniques are enhancing our understanding of mechanisms of disease; highlighting the complexity of interactions between genes, development, and environment in the manifestation of health and disease; and becoming part of the clinical armamentarium for the care of patients. Some of these technologies and their clinical potential are briefly reviewed in this paper.

Caesarean section: impact on mother and child

Maternal/foetal morbidity/mortality consequent to uterine rupture, placenta previa/increta and stillbirth may occur in repeat caesarean section (CS). Elective CS before 39 weeks increases respiratory complications, hypoglycaemia, sepsis and intensive care unit admissions. Different gut colonization in neonates born by CS accounts for increased incidence of food allergy, asthma and possibly type 1 diabetes. Epigenetic changes might be responsible - among others - for childhood malignancies.

CONCLUSION

Decision for primary CS should take into consideration possible maternal/neonatal complications.

Probiotics in the treatment and prevention of allergies in children

Several studies on the pathogenesis of allergy both in man and experimental animals continue to show the importance of commensal bacteria in the gastrointestinal tract in stimulating and directing the immune system. The interest in modulating commensal bacteria flora with pre- and probiotics to prevent and treat food allergy has multiplied in recent years. We recently studied 230 infants with atopic dermatitis and suspected cow’s milk allergy. The infants were randomly allocated to groups which received Lactobacillus GG (LGG), a mixture of four probiotic strains (MIX) or placebo for 4 weeks. We inferred that probiotics induce systemically detectable low-grade inflammation, which may explain the clinical effects and the secretion pattern of cytokines induced by PBMC. To study the ability of probiotics to prevent allergy in children, we recruited 1223 pregnant women carrying fetuses at increased risk of allergy for a double-blind placebo-controlled trial. Mothers used a mixture of four probiotic bacteria or a placebo from the 36th week of gestation. Their infants received the same probiotics plus prebiotic galacto-oligosaccharides for 6 months. At the 2-year follow-up, a total of 925 infants participated. The cumulative incidence of allergic disease did not differ significantly between the synbiotic and the placebo group. However, synbiotics significantly reduced eczema. The preventive effect of synbiotics was more pronounced against IgE-associated diseases. At the 5 year follow-up, 891(88%) of the 1018 intention-to-treat infants attended. In the probiotic and placebo groups, frequencies of allergic symptoms and IgE-associated allergic disease and sensitization were similar, and the frequencies of eczema did not differ between the groups. Atopic eczema, allergic rhinitis and asthma appeared equal frequency in the groups. However, less IgE-associated allergic disease occurred in the cesarean-delivered infants given probiotics. In cesarean-delivered childen, we noticed a delayed rise in bifidobacteria recovery in placebo-treated children which was corrected by pro- and prebiotic supplementation. Indications from studies of feces and blood at the age 6 months suggest that probiotics may enhance both inflammation and immune defence of the gut. The probiotic treatment further stimulated maturation of the immune system since the infants given probiotics showed increased resistance to respiratory infections and improved vaccine antibody responses.

Perinatal programming of asthma: the role of gut microbiota

Perinatal programming, a dominant theory for the origins of cardiovascular disease, proposes that environmental stimuli influence developmental pathways during critical periods of prenatal and postnatal development, inducing permanent changes in metabolism. In this paper, we present evidence for the perinatal programming of asthma via the intestinal microbiome. While epigenetic mechanisms continue to provide new explanations for the programming hypothesis of asthma development, it is increasingly apparent that the intestinal microbiota plays an independent and potentially interactive role. Commensal gut bacteria are essential to immune system development, and exposures disrupting the infant gut microbiota have been linked to asthma. This paper summarizes the recent findings that implicate caesarean delivery, breastfeeding, perinatal stress, probiotics, and antibiotics as modifiers of infant gut microbiota in the development of asthma.

The association of mode of delivery and common childhood illnesses

Participants enrolled in a randomized control trial (RCT) were eligible for this cross-sectional study to determine if children born via cesarean (C)-section had higher rates of common infectious diseases and change in normal daily activities due to illness than children born vaginally. The RCT collected parent-reported health information and mode of delivery was assessed during follow-up calls. Parent-reported rates of infectious sequelae and changes in daily activities were compared between C-section and vaginally delivered children. In total, 72.4% of the 522 children were delivered vaginally. After accounting for age, siblings, breast-feeding as an infant, and clustering within families, C-section delivered children had significantly higher rates of cumulative infectious diseases, lower respiratory tract infections, and cough than vaginally born children. Mode of delivery appears to have some lasting effect on child health 3 to 6 years after birth, specifically respiratory health. Further research is imperative to elucidate the causative effect of mode of delivery on child health.

Early colonization with a group of Lactobacilli decreases the risk for allergy at five years of age despite allergic heredity

Background

Microbial deprivation early in life can potentially influence immune mediated disease development such as allergy. The aims of this study were to investigate the influence of parental allergy on the infant gut colonization and associations between infant gut microbiota and allergic disease at five years of age.

Methods and Findings

Fecal samples were collected from 58 infants, with allergic or non-allergic parents respectively, at one and two weeks as well as at one, two and twelve months of life. DNA was extracted from the fecal samples and Real time PCR, using species-specific primers, was used for detection of Bifidobacterium (B.) adolescentis, B. breve, B. bifidum, Clostridium (C.) difficile, a group of Lactobacilli (Lactobacillus (L.) casei, L. paracasei and L. rhamnosus) as well as Staphylococcus (S.) aureus. Infants with non-allergic parents were more frequently colonized by Lactobacilli compared to infants with allergic parents (p = 0.014). However, non-allergic five-year olds acquired Lactobacilli more frequently during their first weeks of life, than their allergic counterparts, irrespectively of parental allergy (p = 0.009, p = 0.028). Further the non-allergic children were colonized with Lactobacilli on more occasions during the first two months of life (p = 0.038). Also, significantly more non-allergic children were colonized with B. bifidum at one week of age than the children allergic at five years (p = 0.048).

Conclusion

In this study we show that heredity for allergy has an impact on the gut microbiota in infants but also that early Lactobacilli (L. casei, L. paracasei, L. rhamnosus) colonization seems to decrease the risk for allergy at five years of age despite allergic heredity.

Oligosaccharides in 4 different milk groups, Bifidobacteria, and Ruminococcus obeum

OBJECTIVES

The aim of this study was to identify a link between the total amount of breast milk oligosaccharides and faecal microbiota composition of newborns at the end of the first month of life, with special attention paid to bifidobacteria, and establish the role, if any, of the different oligosaccharides in determining the gut microbiota composition.

SUBJECTS AND METHODS

Milk oligosaccharide groups were identified by high-performance anion exchange chromatography analysis. DPCRNA from newborns' faecal samples at 30 days of life was isolated and processed by polymerase chain reaction analyses that allow the identification of 6 species of bifidobacteria (adolescentis, bifidum, breve, catenulatum, longum, infantis) and Ruminococcus spp; denaturing gradient gel electrophoresis analysis was also performed.

RESULTS

No substantial differences in bifidobacteria species composition within milk groups 1, 2, and 3 were observed; however, infants fed with group 4 milk show a microbiota characterised by a greater frequency of Bifidobacteria adolescentis and the absence of Bifidobacteria catenulatum. For the first time, a high percentage of the Ruminococcus genus in infants fed with all milk groups was found.

CONCLUSIONS

Our data show that milk groups 1, 2, and 3, containing an amount of oligosaccharides ranging within 10 to 15 g/L, share a substantially identical composition of the intestinal microbiota in breast-fed infants, despite quali-quantitative difference in oligosaccharides content. Newborns taking milk with only 5 g/L of oligosaccharides (group 4) harbour a different intestinal microbiota.

Cesarean delivery is associated with an increased risk of obesity in adulthood in a Brazilian birth cohort study

BACKGROUND

Obesity is epidemic worldwide, and increases in cesarean delivery rates have occurred in parallel.

OBJECTIVE

This study aimed to determine whether cesarean delivery is a risk factor for obesity in adulthood in a birth cohort of Brazilian subjects.

DESIGN

We initiated a birth cohort study in Ribeirão Preto, southeastern Brazil, in 1978. A randomly selected sample of 2057 subjects from the original cohort was reassessed in 2002-2004. Type of delivery, birth weight, maternal smoking, and schooling were obtained after birth. The following data from subjects were collected at 23-25 y of age: body mass index (BMI; in kg/m(2)), physical activity, smoking, and income. Obesity was defined as a BMI ≥30. A Poisson multivariable model was performed to determine the association between cesarean delivery and BMI.

RESULTS

The obesity rate in adults born by cesarean delivery was 15.2% and in those born by vaginal delivery was 10.4% (P = 0.002). Adults born by cesarean delivery had an increased risk (prevalence ratio: 1.58; 95% CI: 1.23, 2.02) of obesity at adulthood after adjustments.

CONCLUSION

We hypothesize that increasing rates of cesarean delivery may play a role in the obesity epidemic worldwide.

The role of microbes in developmental immunologic programming

The role of microorganisms in the gastrointestinal tract has undergone significant modification in the past few decades with new observations from clinical, epidemiologic, and basic science research. We now know that the perception of these gut microbes as pathogens or even as commensals is somewhat outdated. It is becoming increasingly clear that the gut microbiome plays an important role in a host of activities including digestion, protection from potentially pathogenic organisms, and the regulation and development of the host immune system. The complex interactions between microbes and host combined with recent clinical observations and epidemiologic trends may point to the convergence of two well-supported (though imperfect) hypotheses: the "hygiene hypothesis" and the "fetal programming hypothesis." We are beginning to understand that exposure to microbes before conception, during gestation, and in the neonatal period have profound effects on the developing immune system. Recent observations from a variety of fields help support the expansion of the "fetal programming hypothesis" to a host-microbe corollary that microbe-host interactions at critical windows influence the future immune phenotype, the maintenance of immune health, and the development of immune-mediated disease.

Intestinal microflora and body mass index during the first three years of life: an observational study

Background

Recent research on obesity has demonstrated that the intestinal microflora can have an important influence on host energy balance. The aim of the study was to investigate the relationship between the intestinal microflora and the body mass index in the first 3 years of life.

Results

In a prospective study, a faecal sample from 138 infants was taken at the age of 3, 26 and 52 weeks and cultured on selective media for 6 bacterial genera. Between the age of 1 and 3 years the Body Mass Index Standard Deviation Score (BMI SDS) of these children was determined. The association between the intestinal flora and BMI SDS was assessed for each bacterial genus. A positive correlation was found between the Bacteroides fragilis concentration and the BMI SDS at the age of 3 and 26 weeks. The Staphylococcus concentration showed a negative correlation with the BMI SDS at the age of 3 and 52 weeks. A low intestinal ratio of Staphylococcus/Bacteroides fragilis at the age of 3 weeks, corresponding to a low Staphylococcus and a high Bacteroides fragilis concentration, was associated with a higher BMI SDS during the first three years of life.

Conclusion

High intestinal Bacteroides fragilis and low Staphylococcus concentrations in infants between the age of 3 weeks and 1 year were associated with a higher risk of obesity later in life. This study could provide new targets for a better and more effective modulation of the intestinal microflora in infants.

Pathogenicity island markers, virulence determinants malX and usp, and the capacity of Escherichia coli to persist in infants' commensal microbiotas

Virulence-associated genes in bacteria are often located on chromosomal regions, termed pathogenicity islands (PAIs). Several PAIs are found in Escherichia coli strains that cause extraintestinal infections, but their role in commensal bowel colonization is unknown. Resident strains are enriched in adhesins (P fimbriae and type 1 fimbriae), capsular antigens (K1 and K5), hemolysin, and aerobactin and mostly belong to phylogenetic group B2. Here, we investigated whether six pathogenicity islands and the virulence determinants malX and usp are associated with fitness of E. coli in the infant bowel microbiota. E. coli strains isolated from stools of 130 Swedish infants during the first year of life were examined for their carriage of PAI markers, malX, and usp by PCR. Carriage was related to strain persistence: long-term colonizers (≥12 months) carried significantly more of PAI II from strain CFT703 (II(CFT703)), IV(536,) and II(J96) and malX and usp than intermediate colonizers (1 to 11 months) and transient strains (<3 weeks). The accumulation of PAI markers in each individual strain correlated positively with its time of persistence in the colon. Phylogenetic group B2 accounted for 69% of long-term colonizers, 46% of intermediate colonizers and 14% of transient strains. These results support the hypothesis that some bacterial traits contributing to extraintestinal infections have in fact evolved primarily because they increase the fitness of E. coli in its natural niche, the colon; accordingly, they may be regarded as fitness islands in the gut.

Contribution of the intestinal microbiota to human health: from birth to 100 years of age

Our intestinal tract is colonized since birth by multiple microbial species that show a characteristic succession in time. Notably the establishment of the microbiota in early life is important as it appears to impact later health. While apparently stable in healthy adults, the intestinal microbiota is changing significantly during aging. After 100 years of symbiosis marked changes have been observed that may relate to an increased level of intestinal inflammation. There is considerable interest in the microbiota in health and disease as it may provide functional biomarkers, the possibility to differentiate subjects, and avenues for interventions. This chapter reviews the present state of the art on the research to investigate the contribution of the intestinal microbiota to human health. Specific attention will be given to the healthy microbiota and aberrations due to disturbances such as celiac disease, irritable bowel syndrome, inflammatory bowel disease, obesity and diabetes, and non-alcoholic fatty liver disease.

Effect of lifestyle factors on Staphylococcus aureus gut colonization in Swedish and Italian infants

In recent years, Staphylococcus aureus has become a common bowel colonizer in Swedish infants. We aimed to identify host factors that determine such colonization. Stool samples from 100 Italian and 100 Swedish infants were obtained on seven occasions during the first year of life and cultured quantitatively for S. aureus. In a subgroup of infants in each cohort, individual strains were identified by random amplified polymorphic DNA analysis. Colonization at each time-point was related to delivery mode, siblings in family and antibiotic treatment. In total, 66% of the Italian and 78% of the Swedish infants had S. aureus in their stools on at least one time-point (p 0.08) and 4% of Italian and 27% of Swedish infants were positive on at least six of the seven time-points investigated (p 0.0001). Most infants analysed regarding strain carriage harboured a single strain in their microbiota for several months. The S. aureus stool populations in colonized infants decreased from 10(7) to 10(4) colony-forming units/g between 1 week and 1 year of age in both cohorts. In multivariate analysis, the strongest predictor for S. aureus colonization was being born in Sweden (OR 3.4 at 1 week of age, p 0.002). Having (an) elder sibling(s) increased colonization at peak phase (OR 1.8 at 6 months, p 0.047). Antibiotic treatment was more prevalent among Italian infants and correlated negatively with S. aureus colonization at 6 months of age (OR 0.3, p 0.01). To conclude, S. aureus is a more common gut colonizer in Swedish than Italian infants, a fact that could not be attributed to feeding or delivery mode.

Mucosal immune system in neonatal period and early infancy

The major mechanisms of mucosal defense in the neonate consist of a variety of nonspecific barriers, and innate and specific adaptive immune responses. The functions of innate immunity in the mucosal surfaces are mediated by host-specific microbial–pathogen recognition receptors, designed to recognize unique microbial-associated molecular patterns integral to the structure of most microorganisms. Other mechanisms include many antimicrobial peptides, macrophages, dendritic cells, complement components and host-derived cellular and soluble products. The important elements of neonatal mucosal adaptive immunity include the inductive sites, such as the Peyer’s patches and other lymphoid structures in the respiratory and gastrointestinal tracts, the nasopharyngeal and sublingual tissues, the subepithelial and intraepithelial sites in most external mucosal surfaces, including the genital tract and the mammary glands. These sites contain lymphoid cells derived by the homing of antigen-activated cells from the inductive sites. Activated B cells, mostly IgA (up to 80%) are detected in the mucosal tissues shortly after birth. However, IgA-producing plasma cells are generally detected in the mucosa approximately 7–10 days of age. With progressive environmental antigenic stimulation, the number of circulating IgA cells increase significantly by 1 month of age. The postnatal development of mucosal immunity is critically influenced by the acquisition and nature of mucosal microflora, and the temporal nature and qualitative and quantitative aspects of dietary antigens and other environmental agents introduced in the neonatal period. Mucosal immune responses are generally protective against disease-producing organisms and environmental macromolecules. The mucosal immune responses may also be pathologic and foster the induction of immunologically mediated disease states and autoimmunity. The development of secretory IgA and other antimicrobial mucosal responses as well as the induction of tolerance in the neonatal period and early infancy are essential for the maintenance of mucosal homeostasis in early childhood and prevention of disease later in life.

New concepts of microbial translocation in the neonatal intestine: mechanisms and prevention

Bacterial translocation from the gastrointestinal tract is an important pathway initiating late-onset sepsis and necrotizing enterocolitis in very low-birth-weight infants. The emerging intestinal microbiota, nascent intestinal epithelia, naive immunity, and suboptimal nutrition (lack of breast milk) have roles in facilitating bacterial translocation. Feeding lactoferrin, probiotics, or prebiotics has presented exciting possibilities to prevent bacterial translocation in preterm infants, and clinical trials will identify the most safe and efficacious prevention and treatment strategies.

Microbiote et probiotiques : impact en santé humaine

All accessible mucous membranes of the human body are colonized by an abundant and diversified microbial flora called microbiota. Recent studies have shown that these microorganisms, long regarded as purely commensal, have essential beneficial effects on human health. Thus, numerous human ailments are linked to dysbiosis; that is, imbalances in the microflora composition. The administration of probiotic microorganisms could, in some situations, provide substantial relief from such disorders. These live microorganisms, which, according to the definition, confer a health benefit to the host when administered in adequate amounts, are often derived from human flora and belong mostly to lactic acid bacteria, in particular to the genus Lactobacillus . The constant improvement of knowledge of the role of human microbiota and the growing popularity of probiotics are now opening the door to new prophylactic and therapeutic strategies in human health.

Role of the gut microbiota in defining human health

The human superorganism is a conglomerate of mammalian and microbial cells, with the latter estimated to outnumber the former by ten to one and the microbial genetic repertoire (microbiome) to be approximately 100-times greater than that of the human host. Given the ability of the immune response to rapidly counter infectious agents, it is striking that such a large density of microbes can exist in a state of synergy within the human host. This is particularly true of the distal gastrointestinal (GI) tract, which houses up to 1000 distinct bacterial species and an estimated excess of 1 x 10(14) microorganisms. An ever-increasing body of evidence implicates the GI microbiota in defining states of health and disease. Here, we review the literature in adult and pediatric GI microbiome studies, the emerging links between microbial community structure, function, infection and disease, and the approaches to manipulate this crucial ecosystem to improve host health.

Delivery mode shapes the acquisition and structure of the initial microbiota across multiple body habitats in newborns

Upon delivery, the neonate is exposed for the first time to a wide array of microbes from a variety of sources, including maternal bacteria. Although prior studies have suggested that delivery mode shapes the microbiota's establishment and, subsequently, its role in child health, most researchers have focused on specific bacterial taxa or on a single body habitat, the gut. Thus, the initiation stage of human microbiome development remains obscure. The goal of the present study was to obtain a community-wide perspective on the influence of delivery mode and body habitat on the neonate's first microbiota. We used multiplexed 16S rRNA gene pyrosequencing to characterize bacterial communities from mothers and their newborn babies, four born vaginally and six born via Cesarean section. Mothers' skin, oral mucosa, and vagina were sampled 1 h before delivery, and neonates' skin, oral mucosa, and nasopharyngeal aspirate were sampled <5 min, and meconium <24 h, after delivery. We found that in direct contrast to the highly differentiated communities of their mothers, neonates harbored bacterial communities that were undifferentiated across multiple body habitats, regardless of delivery mode. Our results also show that vaginally delivered infants acquired bacterial communities resembling their own mother's vaginal microbiota, dominated by Lactobacillus, Prevotella, or Sneathia spp., and C-section infants harbored bacterial communities similar to those found on the skin surface, dominated by Staphylococcus, Corynebacterium, and Propionibacterium spp. These findings establish an important baseline for studies tracking the human microbiome's successional development in different body habitats following different delivery modes, and their associated effects on infant health.

Mucosal control of the intestinal microbial community

Although the knowledge of the effects of bacterial colonization on the immune system is rapidly expanding, surprisingly little is known about the immunological mechanisms that shape the intestinal microbial community. Specifically, the complexity of the intestinal microbiota and what constitutes a "healthy" microbial composition has only recently been addressed, facilitated by large-scale metagenomic screens. Containment of such a vast number of different microbes requires tight regulation at the mucosal surface. While beneficial relationships must not be compromised, invading pathogenic bacteria must be dealt with in order to maintain homeostasis. In this review, we will address the latest insights into the role of the mucosal immune system in the control of the microbiota.

Impact of empiric antibiotic regimen on bowel colonization in neonates with suspected early onset sepsis

The purpose of this study was to compare the impact of ampicillin and penicillin used for empiric treatment of early onset sepsis (EOS) on initial gut colonization by aerobic and facultative anaerobic microorganisms. A cluster-randomized, two-center, switch-over study was conducted in two paediatric intensive care units in Estonia and included 276 neonates. Rectal swabs were collected twice a week until discharge or day 60. Colonizing microbes were identified on species level and tested for ampicillin resistance (AR). The number of patients colonized with Gram negative microorganisms and Candida spp was similar in both treatment arms but ampicillin resulted in longer colonization duration (CD) of K. pneumonia (p = 0.012), AR Serratia spp (p = 0.012) and Candida spp (p = 0.02) and penicillin in that of AR Acinetobacter spp (p = 0.001). As for Gram positive microorganisms penicillin treatment was associated with a greater number of colonized patients and higher CD of Enterococcus spp and S. aureus but lower ones of S. haemolyticus and S. hominis. Influence of ampicillin and penicillin on initial gut colonization is somewhat different but these differences are of low clinical relevance and should not be a limiting step when choosing between these two antibiotics for the empiric treatment of EOS.

Gut health: predictive biomarkers for preventive medicine and development of functional foods

There is an urgent need to develop and validate a series of biomarkers, which accurately measure and inform on how the human gut microbiota can affect human health. The human gut hosts a complex community of micro-organisms, with unique features in each individual. The functional role of this gut microbiota in health and disease is increasingly evident, but poorly understood. Comprehension of this ecosystem implies a significant challenge in the elucidation of interactions between all of its components, but promises a paradigm shift in preventive nutrition and medicine. ‘Omics’ technologies for the first time offer tools of sufficient subtlety to tackle this challenge. However, these techniques must be allied with traditional skills of the microbial physiologist, which are in danger of being lost. Targeting these efforts at the identification of biomarkers associated with gut health will require access to a ‘biobank’ from a pan-European or worldwide observation study, which would include samples taken with appropriate frequency from healthy individuals of different ages. This offers a pragmatic opportunity for a unique food and pharmaceutical industry collaboration.

Ageing and its possible impact on mucosal immune responses

The development, structural diversification, and functional maturation of mammalian immunologic repertoire at mucosal surfaces and the systemic lymphoid tissue is a remarkably dynamic and continuous process, which begins in early fetal life and eventually culminates in variable degree of senescence or cellular death with advancing age. This brief overview will highlight the status of our current understanding of the ontogeny of mucosal immunologic response. The role of mucosal microflora and other environmental macromolecules in the regulation of mucosal immunity relative to the process of ageing will also be reviewed.

Comparative metagenomics and population dynamics of the gut microbiota in mother and infant

Colonization of the gastrointestinal tract (GIT) of human infants with a suitable microbial community is essential for numerous aspects of health, but the progression of events by which this microbiota becomes established is poorly understood. Here, we investigate two previously unexplored areas of microbiota development in infants: the deployment of functional capabilities at the community level and the population genetics of its most abundant genera. To assess the progression of the infant microbiota toward an adult-like state and to evaluate the contribution of maternal GIT bacteria to the infant gut, we compare the infant’s microbiota with that of the mother at 1 and 11 months after delivery. These comparisons reveal that the infant’s microbiota rapidly acquires and maintains the range of gene functions present in the mother, without replicating the phylogenetic composition of her microbiota. Microdiversity analyses for Bacteroides and Bifidobacterium, two of the main microbiota constituents, reveal that by 11 months, the phylotypes detected in the infant are distinct from those in the mother, although the maternal Bacteroides phylotypes were transiently present at 1 month of age. The configuration of genetic variants within these genera reveals populations far from equilibrium and likely to be undergoing rapid growth, consistent with recent population turnovers. Such compositional turnovers and the associated loss of maternal phylotypes should limit the potential for long-term coadaptation between specific bacterial and host genotypes.

Superantigenic Staphylococcus aureus stimulates production of interleukin-17 from memory but not naive T cells

T-helper 17 (Th17) cells are characterized by their production of interleukin-17 (IL-17) and have a role in the protection against infections and in certain inflammatory diseases. Humans who lack Th17 cells are more susceptible to Staphylococcus aureus infections compared to individuals having Th17 cells. S. aureus is part of the commensal skin microflora and also colonize the infant gut. To investigate whether UV-killed S. aureus would be more capable of inducing IL-17 than other commensal bacteria, we stimulated mononuclear cells from adults, infants, and newborns with various gram-positive and gram-negative commensal bacteria. IL-17 was produced from adult memory Th17 cells after stimulation with superantigen-producing S. aureus but not nonsuperantigenic S. aureus or other common commensal gut bacteria. Cells from newborns were poor IL-17 producers after stimulation with S. aureus, whereas in some cases IL-17 was secreted from cells isolated from infants at the age of 4 and 18 months. These results suggest that superantigenic S. aureus are particularly efficient in stimulating IL-17 production and that the cytokine is produced from memory T cells.

The long-term health effects of neonatal microbial flora

PURPOSE OF REVIEW

Colonization of the newborn intestine is a complex process evolving over the first year of life. It is partly responsible for guiding immunologic development within the infant. Given the sharp escalation in immunologic diseases such as allergy and inflammatory bowel disease (IBD), this microbial-host interaction has become the focus of intense interest. DNA-based detection techniques have allowed increased identification of specific microbes involved in this symbiosis.

RECENT FINDINGS

Epidemiologic studies have demonstrated a link between allergic diseases and alterations in the colonizing flora of infants. Concurrently, other work has demonstrated that interactions between gut flora and the intestinal epithelium seem to be central to the pathogenesis of IBD. In both allergy and IBD, certain bacteria seem to provide beneficial, protective effects via immune modulation.

SUMMARY

There is a complex interaction between the bacteria within the developing gut and the immune system of the host. Colonization of the neonatal gut represents a critical window in this process. It appears clear that disruption within this flora has long-term health consequences as diverse as eczema, allergic rhinitis, and IBD. Guided establishment of specific species within the flora may reduce the incidence of these diseases.

Association between early-life factors and risk of child-onset Crohn's disease among Victorian children born 1983-1998: a birth cohort study

BACKGROUND

The incidence of Crohn's disease (CD) with onset before age 16 has increased. Several perinatal characteristics have been associated with CD. Our objective was to examine the temporal change in CD incidence by period of birth and the extent that this could be attributed to perinatal characteristics associated with higher CD risk.

METHODS

A record linkage study was conducted utilizing the perinatal records of Victorian births 1983-1998 inclusive and a state-based CD registry. Proportional hazards models were used to investigate the perinatal factors in relation to the onset of CD by age 16. Further, a nested case control study was conducted to examine the association between sibling exposure and CD risk.

RESULTS

The CD incidence rate for births 1983-1998 was 2.01 (95% confidence interval [CI] 1.79, 2.27) per 100,000 child-years. A birth cohort effect was demonstrated, with higher CD risk for 1992-1998 versus 1983-1991 births (hazard ratio [HR] 1.56; 95% CI 1.18, 2.06). Perinatal characteristics associated with higher CD risk included urban location, higher socioeconomic status, married mother, a congenital abnormality and delivery by elective cesarean section. Sibling exposure during the first 6 years of life was not associated with CD risk. The increased CD incidence among more recent births was not accounted for by changes in these measured perinatal factors.

CONCLUSIONS

The temporal increase in CD incidence documented for births up to 1990 has continued for children born after 1991 and was not accounted for by temporal changes in the measured perinatal factors.

The impact of caesarean delivery and type of feeding on cow's milk allergy in infants and subsequent development of allergic march in childhood

BACKGROUND

The incidence of IgE-mediated cow's milk allergy (CMA) has increased over the last few years. There are several genetic and environmental risk factors that may be related to this allergy and the subsequent allergic march (AM).

METHODS

A prospective, cohort study was conducted in patients recruited into the study between 1998 and 2002. Information on clinical variables and complementary tests, perinatal and obstetric factors and the type of hydrolysed formula used was recorded. A cross sectional study on the prevalence of allergic diseases in this cohort was performed in 2004.

RESULTS

We compared IgE-mediated CMA patients with non-IgE-mediated CMA patients and found that IgE-mediated CMA is associated with caesarean delivery (OR = 2.14 95% CI: 1.02-4.49), duration of breast feeding (>2 months, OR = 4.14; 95% CI: 2.17-7.89) and the use of supplementary artificial formula whilst breast feeding (OR = 2.86; 95% CI: 1.33-6.13). The factors associated with AM in IgE-mediated CMA patients were caesarean delivery (OR = 0.42; 95% CI: 0.19-0.92) and the use of more extensively hydrolysed high grade hydrolysates (+EH/HGH) (OR = 0.44; 95% CI: 0.20-0.98), both as protective factors.

CONCLUSIONS

Caesarean delivery is demonstrated as being a risk factor for IgE-mediated CMA, but it does not increase the risk of AM in these infants. The use of +EH/HGH appears to protect IgE-mediated CMA patients from eventually developing AM.

Enterocin C, a class IIb bacteriocin produced by E. faecalis C901, a strain isolated from human colostrum

Enterocin C (EntC), a class IIb bacteriocin was purified from culture supernatants of Enterococcus faecalis C901, a strain isolated from human colostrum. Enterocin C consists of two distinct peptides, named EntC1 and EntC2, whose complementary action is required for full antimicrobial activity. The structural genes entC1 and entC2 encoding enterocins EntC1 and EntC2, respectively, and that encoding the putative immunity protein (EntCI) are located in the 9-kb plasmid pEntC, harboured by E. faecalis C901. The N-terminal sequence of both antimicrobial peptides revealed that EntC1 (4284 Da) is identical to Ent1071A, one of the two peptides that form enterocin 1071 (Ent1071), a bacteriocin produced by E. faecalis BFE 1071. In contrast, EntC2 (3867 Da) presents the non-polar alanine residue at position 17 (Ala(17)) instead of the polar threonine residue (Thr(17)) in Ent1071B, the second peptide constituting Ent1071. In spite of peptide similarities, EntC differs from Ent1071 in major aspects, including the complementary activity among its constitutive peptides and its wider inhibitory spectrum of activity. Different amphiphilic alpha-helical conformations between EntC2 and Ent1071B could explain both, acquired complementary activity and increased antimicrobial spectrum.

Intrauterine bacterial growth at birth and risk of asthma and allergic sensitization among offspring at the age of 15 to 17 years

BACKGROUND

Microbial colonization of the airways and intestine during birth might have an effect on the risk of asthma and allergic diseases later in life.

OBJECTIVE

We sought to evaluate the association between intrauterine microbial growth at the time of delivery and the development of asthma and allergic sensitization among offspring.

METHODS

Intrauterine bacterial culture results were recorded at the time of cesarean delivery of 460 children who were born at Kuopio University Hospital during 1990-1992. When the children reached the age of 15 to 17 years, self-administered questionnaires were sent to the mothers, and 382 of the children were also examined by using skin prick tests.

RESULTS

Intrauterine growth of potential pathogenic anaerobic bacteria and Streptococcus species at birth was associated with an increased risk of doctor-diagnosed asthma ever (odds ratio [OR], 4.51 [95% CI, 1.56-13.0]; OR, 2.53 [95% CI, 1.19-5.38]) and doctor-diagnosed current asthma (OR, 7.34 [95% CI, 2.44-22.03]; OR, 3.37 [95% CI, 1.46-7.76]) at the age of 15 to 17 years compared with the risk seen in subjects with negative microbial cultures. These findings remained significant also after applying the Bonferroni correction. No significant association after the Bonferroni correction was detected between intrauterine microbial growth and allergic sensitization among offspring.

CONCLUSION

The results of this study indicated that specific intrauterine microbial growth at the time of birth might increase the risk of asthma among offspring through inflammatory mechanisms. These results indicate new potential targets for future studies on the effects of maternal vaginal microflora and intrauterine infection in the development of asthma among children.

Faecal short chain fatty acid pattern and allergy in early childhood

AIM

To investigate whether functional changes of the gut flora over time were related to sensitization and allergic symptoms at four years of age.

METHODS

The levels of short chain fatty acids (SCFAs) in faecal samples at one (n = 139) and four (n = 53) years of age were related to the development of positive skin prick tests (SPT) and allergic symptoms during the first four years of life.

RESULTS

Faecal acetic (p < 0.01) and propionic (p < 0.01) acids decreased from one to four years of age, while valeric acid (p < 0.001) increased. Low levels of i-butyric (p = 0.01), i-valeric (p = 0.03) and valeric acids (p = 0.02) at one year were associated with questionnaire-reported symptoms of food allergy at four years. Positive SPTs and allergic symptoms at four years were associated with low faecal levels of i-butyric, i-valeric and valeric acids. At one year of age, infants with, as compared to without older siblings had higher median levels of valeric acid.

CONCLUSION

A slow functional maturation of the gut microflora, as measured by faecal levels of SCFAs is associated with allergy both at one and four years. The findings lend further support to an association between allergy and the development of microbial diversity.

Altered early infant gut microbiota in children developing allergy up to 5 years of age

BACKGROUND

Early colonization with bifidobacteria and lactobacilli is postulated to protect children from allergy, while Clostridium (C.) difficile colonization might be associated with allergic disease. Previous studies of infant gut microbiota in relation to subsequent allergy development have mostly employed culture-dependent techniques, studied genera of bacteria and the follow-up period was limited to 2 years.

OBJECTIVE

To relate gut microbiota in early infancy, notably bifidobacteria and lactobacilli at species level, to allergy development during the first 5 years of life and study if environmental factors influence the early infant gut microbiota.

METHODS

Fecal samples were collected at 1 week, 1 month and 2 months after birth from 47 Swedish infants, followed prospectively to 5 years of age. Bacterial DNA was analysed with real-time PCR and related to allergy development, family size as well as endotoxin and Fel d 1 levels in house dust samples. Primers binding to C. difficile, four species of bifidobacteria, two lactobacilli groups and Bacteroides fragilis were used. Children regarded as allergic manifested allergic symptoms and were skin prick test positive during their first 5 years while non-allergic children were neither.

RESULTS

Children who developed allergy were significantly less often colonized with lactobacilli group I (Lactobacillus (L.) rhamnosus, L. casei, L. paracasei), Bifidobacterium adolescentis and C. difficile during their first 2 months. Infants colonized with several Bifidobacterium species had been exposed to higher amounts of endotoxin and grew up in larger families than infants harbouring few species.

CONCLUSION

A more diverse gut microbiota early in life might prevent allergy development and may be related to the previously suggested inverse relationship between allergy, family size and endotoxin exposure.

Establishment of the gut microbiota in Western infants

In adult individuals, the intestinal microbiota comprises several hundred, mostly anaerobic, bacterial species. This complex ecosystem is formed through the successive establishment of different bacteria in infancy and early childhood. Facultative and aerotolerant bacteria establish first, followed by more and more strict anaerobes. The bacteria derive from different sources and the colonization pattern is influenced by delivery mode and environmental factors. Commensal microbes provide the major drive for maturation of the immune system. Increased hygiene appears to have changed the gut flora of Western infants, which may affect the risk of developing immune mediated diseases.

CONCLUSION

It is clear that the process of infant colonization needs to be studied further, since composition of the microbiota may impact on child health.

Is caesarean delivery associated with sensitization to food allergens and IgE-mediated food allergy: a systematic review

Several studies have shown differences in the composition of the gastrointestinal flora of children who develop sensitization to food allergens compared with non-allergic children. It has been hypothesized that changes in the gut microbiota resulting from caesarean section delivery could increase a child's risk of developing food allergy; however, studies examining the relationship between mode of delivery and food allergy have produced conflicting results. The objective of this review was to determine whether there is sufficient evidence to support an association between delivery by caesarean section and the development of sensitization to food allergens and immunoglobulin E (IgE) mediated food allergy. Using predefined inclusion and exclusion criteria, MEDLINE and PubMed were searched for studies investigating the relationship between caesarean section delivery and food allergy. The information on the quality of the studies and results were extracted and analysed systematically. The search identified four relevant studies as per our protocol. Symptomatic food allergy was used as the outcome in two studies and was found to occur more frequently in children born by caesarean section in one study while the second study found no association between food allergy diagnoses and mode of delivery. The other two studies measured levels of food antigen-specific IgE, with both studies showing an increase in sensitization to food allergens among children born by caesarean section. Overall, there is evidence that the risk of developing IgE-mediated sensitization to food allergens is increased among children delivered by caesarean section, however further studies using objectively diagnosed food allergy as the outcome are needed to verify whether this equates to an increase in confirmed food allergy. Future birth cohort studies should control for the effects of mode of delivery when investigating environmental modifiers of food allergy.

Assessment of the bacterial diversity of human colostrum and screening of staphylococcal and enterococcal populations for potential virulence factors

In contrast to breast milk, little is known about the bacterial composition of human colostrum. The objective of this work was to analyze the bacterial diversity of colostrum obtained from healthy women and to characterize the dominant bacterial species for the presence of possible virulence factors. Samples of colostrum obtained from 36 healthy women were inoculated into different culture media. Several isolates from each medium were selected and identified. Staphylococcal and enterococcal isolates were submitted to genetic profiling. One representative of each profile was included in a genetic and phenotypic characterization scheme, including detection of potential virulence traits/genes and sensitivity to antibiotics. Staphylococcus epidermidis and Enterococcus faecalis were the dominant species, followed by Streptococcus mitis, Propionibacterium acnes and Staphylococcus lugdunensis. Among the 48 S. epidermidis isolates selected on the basis of their genetic profiles, the biofilm-related icaD gene and the mecA gene were detected in only 11 and six isolates, respectively. In parallel, 10 enterococcal isolates were also characterized and none of them contained the cylA, vanA, vanB, vanD, vanE and vanG genes. All of them were sensitive to vancomycin. There were no indications that the colostrum samples contained harmful bacteria.

Staphylococcus epidermidis: a differential trait of the fecal microbiota of breast-fed infants

Background

Breast milk is an important source of staphylococci and other bacterial groups to the infant gut. The objective of this work was to analyse the bacterial diversity in feces of breast-fed infants and to compare it with that of formula-fed ones. A total of 23 women and their respective infants (16 breast-fed and 7 formula-fed) participated in the study. The 16 women and their infants provided a sample of breast milk and feces, respectively, at days 7, 14, and 35. The samples were plated onto different culture media. Staphylococcal and enterococcal isolates were submitted to genetic profiling and to a characterization scheme, including detection of potential virulence traits and sensitivity to antibiotics.

Results

The feeding practice had a significant effect on bacterial counts. A total of 1,210 isolates (489 from milk, 531 from breast-fed and 190 from formula-fed infants) were identified. Staphylococcus epidermidis was the predominant species in milk and feces of breast-fed infants while it was less prevalent in those of formula fed-infants. Enterococcus faecalis was the second predominant bacterial species among the fecal samples provided by the breast-fed infants but it was also present in all the samples from the formula-fed ones. The biofilm-related icaD gene and the mecA gene were only detected in a low number of the S. epidermidis strains. Several enterococcal isolates were also characterized and none of them contained the cylA or the vanABDEG antibiotic-resistance genes. All were sensitive to vancomycin.

Conclusion

The presence of S. epidermidis is a differential trait of the fecal microbiota of breast-fed infants. Globally, the staphyloccal isolates obtained from milk and feces of breast-fed infants contain a low number of virulence determinants and are sensitive to most of the antibiotics tested.

Postnatal development of intestinal microflora as influenced by infant nutrition

The postnatal period of a new human being is characterized, from the microbiological point of view, by the formation of a new ecosystem: the microflora of the human gut. In adulthood a number of barriers exert a potent selective action on bacteria arriving from the mouth, but in the very first stage of our life, these barriers are kept at a very low level, temporarily allowing penetration into the gut of bacteria that are not really believed to be "gut related." Moreover, type of delivery (natural vs. cesarean) and feeding (breast vs. bottle feeding) play dramatic roles in determining the microflora composition. In the last decade a number of articles have reported results on neonates' microflora obtained by means of culture-independent analysis. Data obtained by means of these techniques are in agreement with those produced by selective media, but they also provide some new insights about the presence of anaerobic bacteria. The focus of this article is to update knowledge on infants' microflora during the first 6 mo of life.

Antibiotics and allergic disorders in childhood

AIM

This paper explores the possible association between antibiotics prescribed in infancy and allergic disorders, mainly eczema and asthma, in childhood.

BACKGROUND

No-one fully understands why childhood asthma and eczema have become so common. Some authorities suggest that there may be an association between eczema and asthma and antibiotics prescribed in childhood; however, others disagree. METHOD/EVALUATION: The available literature was reviewed to examine the links between prescribed antibiotics and childhood eczema and asthma. FINDINGS/KEY ISSUE: Some, but not all, research indicates that antibiotic administration in pregnancy, childbirth or infancy may be linked to childhood asthma and eczema, but much uncertainty remains. None of the papers identified stated the doses of antibiotics prescribed. In addition, we were unable to locate studies reporting the interactions between antibiotics and the developing immune system.

CONCLUSION

Health care professionals should be selective when prescribing antibiotics. Further prospective work is needed to guide the prescribing of antibiotics in childbirth and infancy.

Gut microbiota of children living in rural south Thailand and urban Singapore

BACKGROUND

An imbalanced prevalence of allergic diseases occurs in the region of South East Asia. It has been suggested that a change in lifestyle associated with improved hygiene and modernization has altered the composition of human gastrointestinal microbiota, and hence susceptibility to allergy.

METHODS

This cross-sectional study was designed to investigate the differences between fecal microbiota in children living in areas with contrasting socioeconomic development. Fecal samples from 73 young children (age 3.0 +/- 0.5) from rural Thailand and 69 age-matched children from urban Singapore were collected and studied using selective culture. Clinical data were also collected using modified ISAAC questionnaires, aiming to identify the key differences in the demographic as well as clinical features between the two study groups.

RESULTS

The two contrasting populations studied differed significantly in multiple lifestyle factors such as family size, antibiotic use and sources of drinking water in the households. Rural children harbored significantly higher counts of lactic acid bacteria (LAB) [7.1 (6.4, 8.3) vs 6.0 (5.3, 7.0) logCFU/g, p < 0.001)], coliforms [8.9 (7.3, 10.2) vs 6.9 (5.7, 7.7) logCFU/g, p < 0.001)] as well as staphylococci [5.3 (4.8, 6.3) vs 4.3 (3.6, 5.0) logCFU/g, p < 0.001)] than their urban counterparts. However, enterococcal counts did not differ between the two groups. No single lifestyle factor could be identified to have caused such differences.

CONCLUSIONS

Certain fecal microbial counts were higher in rural children compared with urban children in South East Asia. Several contrasting home environmental conditions and practices were also identified. These may serve as a basis for future investigation of lifestyle factors underlying the global gradient of the increasing trends of allergic diseases.

Early differences in fecal microbiota composition in children may predict overweight

BACKGROUND

Experimental studies suggest that gut microbiota deviations predispose toward energy storage and obesity.

OBJECTIVE

We wanted to establish whether early gut microbiota composition can guide weight development throughout early childhood.

DESIGN

Overweight and obese children (n = 25) were selected from a prospective follow-up study at the age of 7 y and identified according to the International Obesity Task Force criteria. Normal-weight children (n = 24) were selected from the same cohort and matched for gestational age and body mass index at birth, mode of delivery, probiotic supplementation, duration of breastfeeding, use of antibiotics during infancy, and frequencies of atopic diseases and atopic sensitization. Early fecal microbiota composition was analyzed by fluorescent in situ hybridization (FISH) with microscopic and flow cytometry detection and by quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

The bifidobacterial numbers in fecal samples during infancy, as assessed by the FISH with flow cytometry, were higher in children remaining normal weight, [median: 2.19 x 10(9) cells/g (interquartile range: 1.10-5.28 x 10(9) cells/g)] than in children becoming overweight [1.20 x 10(9) cells/g (0.48-1.59x 10(9) cells/g); P = 0.02]. A similar tendency was found by FISH with microscopic detection and qRT-PCR. The microbiota aberrancy during infancy in children becoming overweight was also associated with a greater number of Staphylococcus aureus [0.64 x 10(6) cells/g (0.33-1.00 x 10(6) cells/g)] than in children remaining normal weight [0.27 x 10(6) cells/g (0.17-0.50 x 10(6) cells/g); P = 0.013].

CONCLUSION

Aberrant compositional development of the gut microbiota precedes overweight, offering new possibilities for preventive and therapeutic applications in weight management.

Caesarean delivery and risk of atopy and allergic disease: meta-analyses

BACKGROUND

Studies of delivery by caesarean section (c-section) and the offspring's risk of allergic diseases are of current interest due to concerns about the increased use of c-section in many countries. However, previous studies have reported inconsistent findings.

OBJECTIVE

We investigated whether delivery by c-section is associated with an increased risk of atopy and allergic disease by reviewing the literature, performing a meta-analysis, and assessing publication bias.

METHODS

We used a systematic literature search of MEDLINE (1966 to May 2007). Six common allergic outcomes were included: food allergy/food atopy, inhalant atopy, eczema/atopic dermatitis, allergic rhinitis, asthma, and hospitalization for asthma. For each outcome a meta-analysis was performed, where a summary odds ratio (OR) was calculated taking into account heterogeneity between the study-specific relative risks. Publication bias was assessed using the funnel plot method.

RESULTS

We identified 26 studies on delivery by c-section and one or more of the six allergic outcomes. C-section was associated with an increased summary OR of food allergy/food atopy (OR 1.32, 95% CI 1.12-1.55; six studies), allergic rhinitis (OR 1.23, 95% CI 1.12-1.35; seven studies), asthma (OR 1.18, 95% CI 1.05-1.32; 13 studies), and hospitalization for asthma (OR 1.21, 95% CI 1.12-1.31; seven studies), whereas there was no association with inhalant atopy (OR 1.06, 95% CI 0.82-1.38; four studies) and eczema/atopic dermatitis (OR 1.03, 95% CI 0.98-1.09; six studies). Funnel plots indicated that the association with food allergy/food atopy could be difficult to interpret due to publication bias. For each significant association with an allergic outcome, only 1-4% of cases were attributable to c-section.

CONCLUSION

Delivery by c-section is associated with a moderate risk increase for allergic rhinitis, asthma, hospitalization for asthma, and perhaps food allergy/food atopy, but not with inhalant atopy or atopic dermatitis. The increased use of c-section during the last decades is unlikely to have contributed much to the allergy epidemic observed during the same period.

Is meconium from healthy newborns actually sterile?

In a previous study, bacteria were able to be isolated from umbilical cord blood of healthy neonates and from murine amniotic fluid obtained by caesarean section. This suggested that term fetuses are not completely sterile and that a prenatal mother-to-child efflux of commensal bacteria may exist. Therefore, the presence of such bacteria in meconium of 21 healthy neonates was investigated. The identified isolates belonged predominantly to the genuses Enterococcus and Staphylococcus. Later, a group of pregnant mice were orally inoculated with a genetically labelled E. fecium strain previously isolated from breast milk of a healthy woman. The labelled strain could be isolated and PCR-detected from meconium of the inoculated animals obtained by caesarean section one day before the predicted date of labor. In contrast, it could not be detected in samples obtained from a non-inoculated control group.

Development of mucosal immune function in the intrauterine and early postnatal environment

PURPOSE OF REVIEW

There is recent evidence that immunological priming can start prenatally or in the very early life phase. This review summarizes recent progress in the field of early gut immunology with special attention to factors contributing to the intrauterine and early postnatal development of mucosal immune responses in the gut.

RECENT FINDINGS

Development and maturation of the fetal gut immune system occurs under close control of the maternal environment. Examples include maternal antibodies, cytokines, sCD14 molecules and bacterial antigens. Mouse experiments reveal that activated T cells can be detected already at birth in the fetal gut, which are supposed to be activated by signals from the maternal microbial gut flora. Human milk sCD14 is involved in the immunological priming of the developing gut immune system to Gram-negative bacteria and modulates the microbial recognition system of the gut. The development of food allergies is associated with consumption of food components like polyunsaturated fatty acids acting prenatally or in the early postnatal life span as immunomodulators.

SUMMARY

The new findings highlight the importance of very early life factors for the development of the mucosal immune functions of the gut. Therefore, the gut might be a new target to establish preventive strategies with regard to different immunologic disorders.