Antibiotic use during infancy promotes a shift in the T(H)1/T(H)2 balance toward T(H)2-dominant immunity in mice

Antibiotic exposure during pregnancy increases risk for childhood atopic diseases: a nationwide cohort study

PURPOSE

The prevalence of atopic diseases has increased in recent decades. A possible link between antibiotic use during pregnancy and childhood atopic disease has been proposed. The aim of this study is to explore the association of antibiotic exposure during pregnancy with childhood atopic diseases from a nationwide, population-based perspective.

METHODS

This was a nationwide population-based cohort study. Taiwan's National Health Insurance Research Database was the main source of data. The pairing of mothers and children was achieved by linking the NHIRD with the Taiwan Maternal and Child Health Database. This study enrolled the first-time pregnancies from 2004 to 2010. Infants of multiple delivery, preterm delivery, and death before 5 years old were excluded. All participants were followed up at least for 5 years. Antenatal antibiotics prescribed to mothers during the pregnancy period were reviewed. Children with more than two outpatient visits, or one admission, with a main diagnosis of asthma, allergic rhinitis, or atopic dermatitis were regarded as having an atopic disease.

RESULTS

A total of 900,584 children were enrolled in this study. The adjusted hazard ratios of antibiotic exposure during pregnancy to childhood atopic diseases were 1.12 for atopic dermatitis, 1.06 for asthma, and 1.08 for allergic rhinitis, all of which reached statistical significance. The trimester effect was not significant. There was a trend showing the higher the number of times a child was prenatally exposed to antibiotics, the higher the hazard ratio was for childhood atopic diseases.

CONCLUSIONS

Prenatal antibiotic exposure might increase the risk of childhood atopic diseases in a dose-dependent manner.

Cesarean section induced dysbiosis promotes type 2 immunity but not oxazolone-induced dermatitis in mice

Delivery by cesarean section (CS) is associated with an altered gut microbiota (GM) colonization and a higher risk of later chronic inflammatory diseases. Studies investigating the association between CS and atopic dermatitis (AD) are contradictive and often biased by confounding factors. The aim of this study was therefore to provide experimental evidence for the association between CS and AD in a mouse model and clarify the role of the GM changes associated with CS. It was hypothesized that CS-delivered mice, and human CS-GM transplanted mice develop severe dermatitis due to early dysbiosis. BALB/c mice delivered by CS or vaginally (VD) as well as BALB/c mice transplanted with GM from CS or VD human donors were challenged with oxazolone on the ear. The severity of dermatitis was evaluated by ear thickness and clinical and histopathological assessment which were similar between all groups. The immune response was assessed by serum IgE concentration, local cytokine response, and presence of immune cells in the draining lymph node. Both CS-delivered mice and mice inoculated with human CS-GM had a higher IgE concentration. A higher proportion of Th2 cells were also found in the CS-GM inoculated mice, but no differences were seen in the cytokine levels in the affected ears. In support of the experimental findings, a human cohort analysis from where the GM samples were obtained found that delivery mode did not affect the children's risk of developing AD. In conclusion, CS-GM enhanced a Th2 biased immune response, but had no effect on oxazolone-induced dermatitis in mice.

Maternal antibiotic exposure and childhood allergies: The Japan Environment and Children's Study

Background

The association of maternal antibiotic exposure during pregnancy with childhood allergic diseases remains unclear.

Objective

We aimed to evaluate the association of maternal exposure to antibiotic use during pregnancy with childhood allergic diseases up to the age of 3 years by using data from a large Japanese birth cohort.

Methods

We analyzed data on 78,678 pregnant women and their offspring aged 0 to 3 years. Prenatal antibiotic exposure was defined as the use of any antimicrobial agent during pregnancy. Information was collected from maternal interviews and medical record transcripts. The outcome variables in this study included preschool asthma, wheezing, food allergy, atopic dermatitis, eczema, allergic rhinoconjunctivitis, and any allergic disease. We used logistic regression analysis to evaluate the association of antibiotic exposure during pregnancy with childhood allergic diseases.

Results

Among the participating mothers, 28.5% used antibiotics during pregnancy. Antibiotic exposure during pregnancy was associated with preschool asthma (adjusted odds ratio [aOR] = 1.12 [95% CI = 1.06-1.19]), wheezing (aOR = 1.11 [95% CI = 1.07-1.15]), allergic rhinoconjunctivitis (aOR = 1.10 [95% CI = 1.03-1.17]) and any allergic disease (aOR = 1.09 [95% CI = 1.05-1.14]) in offspring up to age 3 years. In contrast, maternal antibiotic use was not associated with food allergies, atopic dermatitis, or eczema. Additionally, the significant associations were not influenced by the timing of antibiotic exposure, sex of the infants, or maternal history of allergies.

Conclusion

Maternal antibiotic exposure during pregnancy is associated with an increased risk of childhood respiratory allergies.

Aflatoxin B1 can aggravate BALB/c mice allergy to ovalbumin through changing their Th2 cells immune responses

Foods contaminated by Aflatoxin B₁ (AFB₁) frequently happen in the world and can cause a lot healthy damages to human beings, meanwhile, some of these foods are easily irritate food allergy. To investigate the effect of AFB₁ exposure on food allergy, three doses of AFB₁ were set, including 0.3 μg/kg · bw (LDAF), 7.5 μg/kg · bw (MDAF), and 100.0 μg/kg · bw (HDAF), respectively; food allergy model was constructed by the BALB/c mice allergy to ovalbumin (OVA). The changes of titer in OVA-specific immunoglobulin E (IgE), IgG, IgG1, IgG2a, as well as level of the mMCP-1 in sera were determined by enzyme linked immunosorbent assay (ELISA), respectively; the levels of interleukin (IL-4, IL-5, IL-13) and interferon (IFN)-γ in spleen were separately assessed using ELISA kits, and their relative genes expression were verified by Real-time fluorescence quantitative PCR (Q-PCR); the population of Th1/Th2/Treg cells were analyzed by flow cytometry. Results showed that when OVA-allergic mice were exposed to AFB₁, the production of OVA-specific IgE, IL-4, IL-5 and IL-13, and mMCP-1 were all increased, whereas the level of IFN-γ was decreased; the Th1/Th2 balance was disrupted and the development of Th cells tilted to the Th2 phenotype. The study would contribute to further understand the risk of fungal toxins in food allergy.

Crosstalk between Gut Microbiota and Host Immunity: Impact on Inflammation and Immunotherapy

Gut microbes and their metabolites are actively involved in the development and regulation of host immunity, which can influence disease susceptibility. Herein, we review the most recent research advancements in the gut microbiota-immune axis. We discuss in detail how the gut microbiota is a tipping point for neonatal immune development as indicated by newly uncovered phenomenon, such as maternal imprinting, in utero intestinal metabolome, and weaning reaction. We describe how the gut microbiota shapes both innate and adaptive immunity with emphasis on the metabolites short-chain fatty acids and secondary bile acids. We also comprehensively delineate how disruption in the microbiota-immune axis results in immune-mediated diseases, such as gastrointestinal infections, inflammatory bowel diseases, cardiometabolic disorders (e.g., cardiovascular diseases, diabetes, and hypertension), autoimmunity (e.g., rheumatoid arthritis), hypersensitivity (e.g., asthma and allergies), psychological disorders (e.g., anxiety), and cancer (e.g., colorectal and hepatic). We further encompass the role of fecal microbiota transplantation, probiotics, prebiotics, and dietary polyphenols in reshaping the gut microbiota and their therapeutic potential. Continuing, we examine how the gut microbiota modulates immune therapies, including immune checkpoint inhibitors, JAK inhibitors, and anti-TNF therapies. We lastly mention the current challenges in metagenomics, germ-free models, and microbiota recapitulation to a achieve fundamental understanding for how gut microbiota regulates immunity. Altogether, this review proposes improving immunotherapy efficacy from the perspective of microbiome-targeted interventions.

Azithromycin to Prevent Recurrent Wheeze Following Severe Respiratory Syncytial Virus Bronchiolitis

BACKGROUND

Early-life severe respiratory syncytial virus (RSV) bronchiolitis is a risk factor for childhood asthma. Because azithromycin may attenuate airway inflammation during RSV bronchiolitis, we evaluated whether it would reduce the occurrence of post-RSV recurrent wheeze.

METHODS

We prospectively enrolled 200 otherwise healthy 1- to 18-month-old children hospitalized with RSV bronchiolitis in this single-center, double-blind, placebo-controlled study and randomly assigned them to receive oral azithromycin (10 mg/kg daily for 7 days, followed by 5 mg/kg daily for 7 days) or placebo. Randomization was stratified by recent open-label antibiotic use. The primary outcome was the occurrence of recurrent wheeze, defined as a third episode of post-RSV wheeze over the following 2 to 4 years.

RESULTS

As an indication of the biologic activity of azithromycin, nasal wash interleukin-8 levels, at day 14 after randomization, were lower among azithromycin-treated participants (P<0.01). Despite evidence of biologic activity, azithromycin did not reduce the risk of post-RSV recurrent wheeze (47% in the azithromycin group vs. 36% in the placebo group; adjusted hazard ratio, 1.45; 95% confidence interval [CI], 0.92 to 2.29; P=0.11). Azithromycin also did not modify the risk of recurrent wheeze among participants already receiving other antibiotic treatment at the time of enrollment (hazard ratio, 0.94; 95% CI, 0.43 to 2.07). There was a potential signal among antibiotic-naïve participants who received azithromycin to have an increased risk of recurrent wheeze (hazard ratio, 1.79; 95% CI, 1.03 to 3.1).

CONCLUSIONS

Azithromycin therapy for 14 days during acute severe RSV bronchiolitis did not reduce recurrent wheeze occurrence over the following 2 to 4 years. Our data suggest no benefit of azithromycin administration with the goal of preventing recurrent wheeze in later life. (Funded by the National Heart, Lung, and Blood Institute; ClinicalTrials.gov number, NCT02911935.).

Gut microbiota and allergic diseases in children

The gut microbiota resides in the human gastrointestinal tract, where it plays an important role in maintaining host health. The human gut microbiota is established by the age of 3 years. Studies have revealed that an imbalance in the gut microbiota, termed dysbiosis, occurs due to factors such as cesarean delivery and antibiotic use before the age of 3 years and that dysbiosis is associated with a higher risk of future onset of allergic diseases. Recent advancements in next-generation sequencing methods have revealed the presence of dysbiosis in patients with allergic diseases, which increases attention on the relationship between dysbiosis and the development of allergic diseases. However, there is no unified perspective on the characteristics on dysbiosis or the mechanistic link between dysbiosis and the onset of allergic diseases. Here, we introduce the latest studies on the gut microbiota in children with allergic diseases and present the hypothesis that dysbiosis characterized by fewer butyric acid-producing bacteria leads to fewer regulatory T cells, resulting in allergic disease. Further studies on correcting dysbiosis for the prevention and treatment of allergic diseases are warranted.

Impact of antibiotics on the human microbiome and consequences for host health

It is well established that the gut microbiota plays an important role in host health and is perturbed by several factors including antibiotics. Antibiotic-induced changes in microbial composition can have a negative impact on host health including reduced microbial diversity, changes in functional attributes of the microbiota, formation, and selection of antibiotic-resistant strains making hosts more susceptible to infection with pathogens such as Clostridioides difficile. Antibiotic resistance is a global crisis and the increased use of antibiotics over time warrants investigation into its effects on microbiota and health. In this review, we discuss the adverse effects of antibiotics on the gut microbiota and thus host health, and suggest alternative approaches to antibiotic use.

Dermatan sulfate and chondroitin sulfate from Lophius litulon alleviate the allergy sensitized by major royal jelly protein 1

The objective of the present study was to explore the desensitization effect of dermatan sulfate (DS) and chondroitin sulfate (CS) from Lophius litulon (Ll) on mice sensitized by major royal jelly protein 1 (MRJP1). First, the affinity between six glycosaminoglycans and the MRJP1 polyclonal antibody was measured by the ELISA method. Lophius litulon dermatan sulfate (Ll DS) and Lophius litulon chondroitin sulfate (Ll CS) were selected due to their highest binding affinity. Second, the molecular docking method was used to explore the interaction between Ll DS and MRJP1 and Ll CS and MRJP1. The results showed that Ll DS and Ll CS combined with MRJP1 successfully, which meant a potential function of relieving the MRJP1-caused allergy. Finally, the MRJP1-sensitized mice model was established and confirmed that Ll DS and Ll CS had the desensitization ability to relieve MRJP1-induced allergic symptoms. To validate the conclusion, the relief of allergic symptoms in mice was observed. The production of total IgE, MRJP1-specific IgE and histamine was measured. The desensitization mechanism was further studied by measuring cytokines (IL-4 and IFN-γ) from splenocytes stimulated with MRJP1 in vitro. Based on in vivo and in vitro experiments, it was confirmed that Ll DS and Ll CS have the ability to alleviate MRJP1-induced allergic symptoms, which proposes a potential candidate material against IgE-mediated food allergy.

Intrapartum Group B Streptococcal Prophylaxis and Childhood Allergic Disorders

OBJECTIVES

To determine if maternal intrapartum group B Streptococcus (GBS) antibiotic prophylaxis is associated with increased risk of childhood asthma, eczema, food allergy, or allergic rhinitis.

METHODS

Retrospective cohort study of 14 046 children. GBS prophylaxis was defined as administration of intravenous penicillin, ampicillin, cefazolin, clindamycin, or vancomycin to the mother, ≥4 hours before delivery. Composite primary outcome was asthma, eczema, or food allergy diagnosis within 5 years of age, identified by diagnosis codes and appropriate medication prescription. Allergic rhinitis was defined by using diagnostic codes only and analyzed as a separate outcome. Analysis was a priori stratified by delivery mode and conducted by using Cox proportional hazards model adjusted for multiple confounders and covariates. Secondary analyses, restricted to children retained in cohort at 5 years' age, were conducted by using multivariate logistic regression.

RESULTS

GBS prophylaxis was not associated with increased incidence of composite outcome among infants delivered vaginally (hazard ratio: 1.13, 95% confidence interval [CI]: 0.95-1.33) or by cesarean delivery (hazard ratio: 1.08, 95% CI: 0.88-1.32). At 5 years of age, among 10 404 children retained in the study, GBS prophylaxis was not associated with the composite outcome in vaginal (odds ratio: 1.21, 95% CI: 0.96-1.52) or cesarean delivery (odds ratio: 1.17, 95% CI: 0.88-1.56) cohorts. Outcomes of asthma, eczema, food allergy, separately, and allergic rhinitis were also not associated with GBS prophylaxis.

CONCLUSIONS

Intrapartum GBS prophylaxis was not associated with subsequent diagnosis of asthma, eczema, food allergy, or allergic rhinitis in the first 5 years of age.

Maternal antibiotic exposure during pregnancy and the risk of allergic diseases in childhood: A meta-analysis

BACKGROUND

Increasing studies suggest that antibiotic exposure during pregnancy may increase the risk of childhood allergic diseases; however, controversy still exists. Thus, we conducted this meta-analysis to evaluate the association between antibiotic use during pregnancy and childhood asthma/wheeze, eczema/atopic dermatitis, and food allergy.

METHODS

CENTRAL, EMBASE, and PubMed were searched for studies up to July 20, 2020. Cohort studies and case-control studies that estimated the association of antibiotic exposure in pregnancy with the risk of childhood asthma/wheeze, eczema/atopic dermatitis, and food allergy were included. A random-effects model or fixed-effects model was used to calculate the pooled estimates. The quality of the included studies was assessed by the Newcastle-Ottawa Scale (NOS). Stata12.0 software was used to analyze the association through a meta-analysis.

RESULTS

A total of 26 studies were included in the meta-analysis. The results showed that maternal antibiotic exposure in pregnancy and the summary OR for the risk of childhood asthma/wheeze was 1.29 (95% CI = 1.16-1.43), the summary OR for eczema/atopic dermatitis was 1.62 (95% CI = 1.16-2.27), and the pooled OR for food allergy was 1.36 (95% CI = 0.94-1.96).

CONCLUSIONS

Our results indicated that maternal antibiotic use during pregnancy might increase the risk of asthma/wheeze and eczema/atopic dermatitis but not food allergy in children. Further studies with larger sample size and robust multivariable adjustment are needed to confirm our findings. Nevertheless, the appropriate use of antibiotics during pregnancy is incredibly important, and healthcare professionals should be selective when prescribing antibiotics for pregnant women.

Dirty mice join the immunologist's toolkit

The microbiota is a driving force that influences host physiological functions. In this review, we discuss some of the methods that have been used in the pursuit of relevant host-microbiota interactions that control immune fitness and disease susceptibility, with a focus on dirty mice which have been recently incorporated in the immunologist's toolkit.

Vaccine Interactions With the Infant Microbiome: Do They Define Health and Disease?

Over the past decade, there has been a growing awareness of the vital role of the microbiome in the function of the immune system. Recently, several studies have demonstrated a relationship between the composition of the microbiome and the vaccine-specific immune response. As a result of these findings, the administration of probiotics has been proposed as a means of boosting vaccine-specific immunity. Early results have so far been highly inconsistent, with little evidence of sustained benefit. To date, a precise determination of the aspects of the microbiome that impact immunity is still lacking, and the mechanisms of action are also unknown. Further investigations into these questions are necessary to effectively manipulate the microbiome for the purpose of boosting immunity and enhancing vaccine-specific responses in infants. In this review, we summarize recent studies aimed at altering the neonatal gut microbiome to enhance vaccine responses and highlight gaps in knowledge and understanding. We also discuss research strategies aimed at filling these gaps and developing potential therapeutic interventions.

Antibiotic-induced gut dysbiosis and barrier disruption and the potential protective strategies

The oral antibiotic therapies administered widely to people and animals can cause gut dysbiosis and barrier disruption inevitably. Increasing attention has been directed toward antibiotic-induced gut dysbiosis, which involves a loss of diversity, changes in the abundances of certain taxa and consequent effects on their metabolic capacity, and the spread of antibiotic-resistant bacterial strains. Treatment with beta-lactam, glycopeptide, and macrolide antibiotics is associated with the depletion of beneficial commensal bacteria in the genera Bifidobacterium and Lactobacillus. The gut microbiota is a reservoir for antibiotic resistance genes, the prevalence of which increases sharply after antibiotic ingestion. The intestinal barrier, which comprises secretory, physical, and immunological barriers, is also a target of antibiotics. Antibiotic induced changes in the gut microbiota composition could induce weakening of the gut barrier through changes in mucin, cytokine, and antimicrobial peptide production by intestinal epithelial cells. Reports have indicated that dietary interventions involving prebiotics, probiotics, omega-3 fatty acids, and butyrate supplementation, as well as fecal microbiota transplantation, can alleviate antibiotic-induced gut dysbiosis and barrier injuries. This review summarizes the characteristics of antibiotic-associated gut dysbiosis and barrier disruption, as well as the strategies for alleviating this condition. This information is intended to provide a foundation for the exploration of safer, more efficient, and affordable strategies to prevent or relieve antibiotic-induced gut injuries.

Antibiotics in early life associate with specific gut microbiota signatures in a prospective longitudinal infant cohort

BACKGROUND

The effects of antibiotics on infant gut microbiota are unclear. We hypothesized that the use of common antibiotics results in long-term aberration in gut microbiota.

METHODS

Antibiotic-naive infants were prospectively recruited when hospitalized because of a respiratory syncytial virus infection. Composition of fecal microbiota was compared between those receiving antibiotics during follow-up (prescribed at clinicians' discretion because of complications such as otitis media) and those with no antibiotic exposure. Fecal sampling started on day 1, then continued at 2-day intervals during the hospital stay, and at 1, 3 and 6 months at home.

RESULTS

One hundred and sixty-three fecal samples from 40 patients (median age 2.3 months at baseline; 22 exposed to antibiotics) were available for microbiota analyses. A single course of amoxicillin or macrolide resulted in aberration of infant microbiota characterized by variation in the abundance of bifidobacteria, enterobacteria and clostridia, lasting for several months. Recovery from the antibiotics was associated with an increase in clostridia. Occasionally, antibiotic use resulted in microbiota profiles associated with inflammatory conditions.

CONCLUSIONS

Antibiotic use in infants modifies especially bifidobacterial levels. Further studies are warranted whether administration of bifidobacteria will provide health benefits by normalizing the microbiota in infants receiving antibiotics.

Infant wheezing and prenatal antibiotic exposure and mode of delivery: a prospective birth cohort study

Introduction: Assessments on whether prenatal antibiotic exposure and mode of delivery increase the risk of wheezing in infants and toddlers are inconsistent. Our goal is to evaluate the association between prenatal antibiotic use and Cesarean section with three subtypes of wheezing in infancy.Methods: An ongoing prospective three generations cohort study provides data on prenatal antibiotic use and mode of delivery. Respective questionnaire data was used to distinguish three subtypes of wheezing: any wheezing, infectious wheezing, and noninfectious wheezing. Repeated measurements of wheezing at 3, 6, and 12 months were analyzed using generalized estimation equations. Latent transition analysis assessed patterns of infant wheezing development in the first year of life.Results: The prevalence of any wheezing was highest at 12 months (40.1%). The prevalence of infectious wheezing was higher (3 months 23.8%, 6 months 33.5%, 12 months 38.5%) than of noninfectious wheezing (3 months 13.0%, 6 months 14.0%, 12 months 11.1%). About 11-13% of children had both infectious and noninfectious wheezing at 3, 6, and 12 months (3 months 10.7%, 6 months 13.9%, 12 months 13.1%). Children born via Cesarean section have approximately a 70-80% increase in the risk of any wheezing (RR = 1.83, 95% CI 1.29-2.60) and of infectious wheezing (RR = 1.72, 95% CI 1.18-2.50).Conclusions: Analyses of infectious and noninfectious wheezing subtypes suggests that children born by Cesarean sections may be more susceptible to infectious wheezing, warranting investigations into microbial factors of infectious wheezing. No significant associations were found between prenatal antibiotic exposure and wheezing types.

Early life microbiome perturbation alters pulmonary responses to ozone in male mice

Early life changes in the microbiome contribute to the development of allergic asthma, but little is known about the importance of the microbiome for other forms of asthma. Ozone is a nonatopic asthma trigger that causes airway hyperresponsiveness and neutrophil recruitment to the lungs. The purpose of this study was to test the hypothesis that early life perturbations in the gut microbiome influence subsequent responses to ozone. To that end, we placed weanling mouse pups from The Jackson Laboratories or from Taconic Farms in sex-specific cages either with other mice from the same vendor (same-housed) or with mice from the opposite vendor (cohoused). Mice were maintained with these cagemates until use. The gut microbial community differs in mice from Jackson Labs and Taconic Farms, and cohousing mice transfers fecal microbiota from one mouse to another. Indeed, 16S rRNA sequencing of fecal DNA indicated that differences in the gut microbiomes of Jackson and Taconic same-housed mice were largely abolished when the mice were cohoused. At 10-12 weeks of age, mice were exposed to room air or ozone (2 ppm for 3 hr). Compared to same-housed mice, cohoused male but not female mice had reduced ozone-induced airway hyperresponsiveness and reduced ozone-induced increases in bronchoalveolar lavage neutrophils. Ozone-induced airway hyperresponsiveness was greater in male than in female mice and the sex difference was largely abolished in cohoused mice. The data indicate a role for early life microbial perturbations in pulmonary responses to a nonallergic asthma trigger.

Role of early life immune regulation in asthma development

Development of childhood asthma is complex with a strong interaction of genetic, epigenetic, and environmental factors. Ultimately, it is critical how the immune system of a child responds to these influences and whether effective strategies for a balanced and healthy immune maturation can be assured. Pregnancy and early childhood are particularly susceptible for exogenous influences due to the developing nature of a child’s immune system. While endogenous influences such as family history and the genetic background are immutable, epigenetic regulations can be modulated by both heredity and environmental exposures. Prenatal influences such as a mother’s nutrition, smoking, or infections influence the complex interplay of innate and adaptive immune regulation as well as peri- and postnatal influences including mode of delivery. Early in life, induction and continuous training of healthy maturation include balanced innate immunity (e.g., via innate lymphoid cells) and an equilibrium of T-cell subpopulations (e.g., via regulatory T cells) to counter-regulate potential pro-inflammatory or exuberant immune reactions. Later in childhood, rather compensatory immune mechanisms are required to modulate deviant regulation of a child’s already primed immune trajectory. The specific effects of exogenous and endogenous influences on a child’s maturing immune system are summarized in this review, and its importance and potential intervention for early prevention and treatment strategies are delineated.

A Collaborative Multicenter QI Initiative to Improve Antibiotic Stewardship in Newborns

OBJECTIVES

To determine if NICU teams participating in a multicenter quality improvement (QI) collaborative achieve increased compliance with the Centers for Disease Control and Prevention (CDC) core elements for antibiotic stewardship and demonstrate reductions in antibiotic use (AU) among newborns.

METHODS

From January 2016 to December 2017, multidisciplinary teams from 146 NICUs participated in Choosing Antibiotics Wisely, an Internet-based national QI collaborative conducted by the Vermont Oxford Network consisting of interactive Web sessions, a series of 4 point-prevalence audits, and expert coaching designed to help teams test and implement the CDC core elements of antibiotic stewardship. The audits assessed unit-level adherence to the CDC core elements and collected patient-level data about AU. The AU rate was defined as the percentage of infants in the NICU receiving 1 or more antibiotics on the day of the audit.

RESULTS

The percentage of NICUs implementing the CDC core elements increased in each of the 7 domains (leadership: 15.4%-68.8%; accountability: 54.5%-95%; drug expertise: 61.5%-85.1%; actions: 21.7%-72.3%; tracking: 14.7%-78%; reporting: 6.3%-17.7%; education: 32.9%-87.2%; P < .005 for all measures). The median AU rate decreased from 16.7% to 12.1% (P for trend < .0013), a 34% relative risk reduction.

CONCLUSIONS

NICU teams participating in this QI collaborative increased adherence to the CDC core elements of antibiotic stewardship and achieved significant reductions in AU.

Early-Life Exposure to Oral Antibiotics and Lung Function Into Early Adulthood

BACKGROUND

Although there is ongoing debate regarding the impact of early postnatal exposure to antibiotics on the development of asthma, the possibility that antibiotic exposure may impair lung function has not previously been examined. Furthermore, it is unclear if specific types of antibiotics may have a greater effect, or if children with genetic mutations in the oxidative stress response glutathione S-transferase (GST) superfamily may be at greater risk.

METHODS

Parent-reported data of childhood antibiotic use from birth to 2 years, including type and indication, were collected from a birth cohort of 620 infants with a family history of allergy. Spirometry was performed at age 12 and 18 years, and results are presented as z scores. Participants were genotyped for GST-P, GST-M, and GST-T polymorphisms. Linear regression models were used to investigate the associations while adjusting for confounding factors.

RESULTS

Neither increasing days of exposure nor earlier exposure to antibiotics was associated with reduced FEV₁ (at 18 years, per doubling of days of exposure = -0.03 z score units; 95% CI, -0.11 to 0.04) or FVC (< 0.01; 95% CI, -0.08 to 0.07). There was no evidence that GST-risk polymorphisms (M1, P1, and T1) increased susceptibility, and specific types of antibiotics also did not increase risk of lung function deficits.

CONCLUSIONS

Increasing exposure to oral antibiotics in early postnatal life was not associated with reduced lung function in children with a family history of allergic diseases. Although unwarranted use of antibiotics in children should be minimized, concerns regarding long-term lung health should not be a driving influence for this rationalization of use.

Specific class of intrapartum antibiotics relates to maturation of the infant gut microbiota: a prospective cohort study

OBJECTIVE

To evaluate the potential impact of intrapartum antibiotics, and their specific classes, on the infant gut microbiota in the first year of life.

DESIGN

Prospective study of infants in the New Hampshire Birth Cohort Study (NHBCS).

SETTINGS

Rural New Hampshire, USA.

POPULATION OR SAMPLE

Two hundred and sixty-six full-term infants from the NHBCS.

METHODS

Intrapartum antibiotic use during labour and delivery was abstracted from medical records. Faecal samples collected at 6 weeks and 1 year of age were characterised by 16S rRNA sequencing, and metagenomics analysis in a subset of samples.

EXPOSURES

Maternal exposure to antibiotics during labour and delivery.

MAIN OUTCOME MEASURE

Taxonomic and functional profiles of faecal samples.

RESULTS

Infant exposure to intrapartum antibiotics, particularly to two or more antibiotic classes, was independently associated with lower microbial diversity scores as well as a unique bacterial community at 6 weeks (GUnifrac, P = 0.02). At 1 year, infants in the penicillin-only group had significantly lower α diversity scores than infants not exposed to intrapartum antibiotics. Within the first year of life, intrapartum exposure to penicillins was related to a significantly lower increase in several taxa including Bacteroides, use of cephalosporins was associated with a significantly lower rise over time in Bifidobacterium and infants in the multi-class group experienced a significantly higher increase in Veillonella dispar.

CONCLUSIONS

Our findings suggest that intrapartum antibiotics alter the developmental trajectory of the infant gut microbiome, and specific antibiotic types may impact community composition, diversity and keystone immune training taxa.

TWEETABLE ABSTRACT

Class of intrapartum antibiotics administered during delivery relates to maturation of infant gut microbiota.

Association between extrauterine growth restriction and changes of intestinal flora in Chinese preterm infants

The aim of the study was to investigate any association between extrauterine growth restriction (EUGR) and intestinal flora of <30-week-old preterm infants. A total of 59 preterm infants were assigned to EUGR (n=23) and non-EUGR (n=36) groups. Intestinal bacteria were compared by using high-throughput sequencing of bacterial rRNA. The total abundance of bacteria in 344 genera (7568 v. 13,760; P<0.0001) and 456 species (10,032 v. 18,240; P<0.0001) was significantly decreased in the EUGR group compared with the non-EUGR group. After application of a multivariate logistic model and adjusting for potential confounding factors, as well as false-discovery rate corrections, we found four bacterial genera with higher and one bacterial genus with lower abundance in the EUGR group compared with the control group. In addition, the EUGR group showed significantly increased abundances of six species (Streptococcus parasanguinis, Bacterium RB5FF6, two Klebsiella species and Microbacterium), but decreased frequencies of three species (one Acinetobacter species, Endosymbiont_of_Sphenophorus_lev and one Enterobacter_species) compared with the non-EUGR group. Taken together, there were significant changes in the intestinal microflora of preterm infants with EUGR compared to preterm infants without EUGR.

Antibiotics and autoimmune and allergy diseases: Causative factor or treatment?

The newborn infant emerges from an almost sterile environment into a world of bacteria. Bacteria colonize the infant's skin, lungs, and, of most importance, the gut. The process of bacterial colonization is coordinated, and each body niche acquires a unique composition of bacteria. In the gut, most bacteria belong to the Firmicutes and Bacteroidetes phyla, while Actinobacteria and Proteobacteria are far less abundant. Some of these bacteria possess strong immunoregulatory properties. Bacterial colonization is essential to skew the newborn's immune response away from the allergy-favoring Type-2 response towards a Type-1 immune response, which is essential for pathogen elimination. Imbalance between Type 1 and Type 2 responses, however, can promote autoimmunity. In addition, the microbiota shapes immune responses in adults. Autoimmune and allergic diseases are commonly associated with an altered composition of resident bacteria, which is known as dysbiosis. Perhaps the most common cause of disruption and alteration of the bacterial colonization of newborns is the use of antibiotics. It is not known whether the dysbiosis precedes or is the consequence of allergic and autoimmune disorders, and whether antibiotics can be a trigger for these disorders, depending on the type of antibiotic used and the maturity of immune system. In this review, we discuss the development of the microbiota in different body niches and their immunomodulatory potential. We evaluate the impact of antibiotics, both in mice and in humans, on microbial communities and how that may impact the development and manifestation of diseases through all stages of life: the prenatal period, childhood, and adulthood.

Postnatal Administration of Lactobacillus rhamnosus HN001 Ameliorates Perinatal Broad-Spectrum Antibiotic-Induced Reduction in Myelopoiesis and T Cell Activation in Mouse Pups

SCOPE

This study addresses whether administration of Lactobacillus rhamnosus HN001 could mitigate the effects of a compromised gut microbiota on the composition of mature leukocytes and granulocyte-macrophage progenitor cells (GMPs) in newborn mice.

METHODS AND RESULTS

Pregnant dams receive oral broad-spectrum antibiotics, which dramatically decrease the gut microbial composition analyzed by 16S rRNA sequencing. Perinatal antibiotic treatment decreases the proportions of bone marrow (BM) GMPs (postnatal day (PND2): 0.5% vs 0.8%, PND4: 0.2% to 0.6%) and mature granulocytes (33% vs 24% at PND2), and spleen granulocytes (7% vs 17% at PND2) and B cells (PND2:18% vs 28%, PND4:11% vs 22%). At PND35, T helper (Th) cells (20% vs 14%) and cytotoxic T (Tc) cells (10% vs 8%) decrease in the spleen. Oral administration of L. rhamnosus HN001 to neonatal pups (PND1-7) restores the antibiotic-induced changes of GMPs and granulocytes in BM and spleen, and further increases splenic granulocytes in control pups. At PND35, splenic proportions of B and Th but not Tc cells are restored.

CONCLUSION

Postnatal administration of a single bacterial strain efficiently restores granulopoiesis and most T cell activation in neonatal mice that suffer from a perinatal antibiotic-induced compromised gut microbiota at birth.

Wheezing and infantile colic are associated with neonatal antibiotic treatment

BACKGROUND

Cohort studies have suggested that early-life antibiotic treatment is associated with increased risk of atopy. We determined whether antibiotic treatment already in the first week of life increases the risk of atopic and non-atopic disorders.

METHODS

The INCA study is a prospective observational birth cohort study of 436 term infants, with follow-up of 1 year; 151 neonates received broad-spectrum antibiotics for suspected neonatal infection (AB+), vs a healthy untreated control group (N = 285; AB-). In the first year, parents recorded daily (non-) allergic symptoms. At 1 year, doctors' diagnoses were registered and a blood sample was taken (n = 205).

RESULTS

Incidence of wheezing in the first year was higher in AB+ than AB- (41.0% vs 30.5%, P = .026; aOR 1.56 [95%CI 0.99-2.46, P = .06]). Infantile colics were more prevalent in AB+ compared to AB- (21.9% and 14.4% P = .048), and antibiotic treatment was an independent risk factor for infantile colics (aOR 1.66 (95%CI 1.00-2.77) P = .05). Allergic sensitization (Phadiatop >0.70kUA/L) showed a trend toward a higher risk in AB+ (aOR 3.26 (95%CI 0.95-11.13) P = .06). Incidence of eczema, infections, and GP visits in the first year were similar in AB+ and AB-.

CONCLUSION

Antibiotic treatment in the first week of life is associated with an increased risk of wheezing and infantile colics. This study may provide a rationale for early cessation of antibiotics in neonates without proven or probable infection.

Influence of changes in the intestinal microflora on the immune function in mice

The composition of the intestinal microbiota is related to the health and immune function of the host. Administration of antibiotics affects the composition of the intestinal microbiota. However, the effects of immune function on the composition of the intestinal microbiota are still unclear. In this study, we investigated the lymphocyte composition and determined the relationships between lymphocyte function and the intestinal microbiota following antibiotic treatment in mice. To change the composition of the intestinal microbiota, mice were treated with or without antibiotics. Analysis of intestinal microbiota was performed by metagenomic analysis targeting 16S rRNA. Lymphocyte subsets of splenocytes were measured by flow cytometry. For functional analysis of T cells, splenocytes were stimulated with concanavalin (Con A), and cytokine gene expression was measured by real-time polymerase chain reaction. Firmicutes were predominant in the control group, whereas Bacteroidetes predominated in the antibiotic-treated group, as determined by metagenomic analysis. The diversity of the microbiota decreased in the antibiotic-treated group. Analysis of lymphocyte subsets showed that CD3⁺ cells decreased, whereas CD19⁺ cells increased in the antibiotic-treated group. All cytokine genes in splenocytes treated with Con A were downregulated in the antibiotic-treated group; in particular, genes encoding interferon-γ, interleukin (IL)-6, and IL-13 significantly decreased. Taken together, these results revealed that changes in the composition of the intestinal microbiota by antibiotic treatment influenced the population of lymphocytes in splenocytes and affected the immune response.

Murine models for mucosal tolerance in allergy

Immunity is established by a fine balance to discriminate between self and non-self. In addition, mucosal surfaces have the unique ability to establish and maintain a state of tolerance also against non-self constituents such as those represented by the large numbers of commensals populating mucosal surfaces and food-derived or air-borne antigens. Recent years have seen a dramatic expansion in our understanding of the basic mechanisms and the involved cellular and molecular players orchestrating mucosal tolerance. As a direct outgrowth, promising prophylactic and therapeutic models for mucosal tolerance induction against usually innocuous antigens (derived from food and aeroallergen sources) have been developed. A major theme in the past years was the introduction of improved formulations and novel adjuvants into such allergy vaccines. This review article describes basic mechanisms of mucosal tolerance induction and contrasts the peculiarities but also the interdependence of the gut and respiratory tract associated lymphoid tissues in that context. Particular emphasis is put on delineating the current prophylactic and therapeutic strategies to study and improve mucosal tolerance induction in allergy.

Influence of antibiotic use in early childhood on asthma and allergic diseases at age 5

BACKGROUND

In the past few decades, the prevalence of allergic diseases has increased rapidly worldwide. At the same time, the overuse of antibiotics has been observed, especially in Japan.

OBJECTIVE

To elucidate the association of early childhood antibiotic use with allergic diseases in later childhood at 5 years of age.

METHODS

Relevant data were extracted from the hospital-based birth cohort study, the Tokyo Children's Health, Illness and Development Study. To identify signs of asthma and allergic diseases in children, the International Study of Asthma and Allergies in Childhood questionnaire was used. Logistic regression models were applied to estimate the effect of antibiotic use on outcomes in later life.

RESULTS

Antibiotic exposure in children within the first 2 years of life was associated with current asthma (adjusted odds ratio [aOR] 1.72, 95% confidence interval [CI] 1.10-2.70), current atopic dermatitis (aOR 1.40, 95% CI 1.01-1.94), and current allergic rhinitis (aOR 1.65, 95% CI 1. 05-2.58) at 5 years of age. Analysis of the associations by type of antibiotics showed that cephem was associated with current asthma (aOR 1.97, 95% CI 1.23-3.16) and current rhinitis (aOR 1.82, 95% CI 1.12-2.93), and macrolide was associated with current atopic dermatitis (aOR 1.58, 95% CI 1.07-2.33).

CONCLUSION

Our findings suggest that antibiotic use within the first 2 years of life was a risk factor for current asthma, current atopic dermatitis, and current allergic rhinitis in 5-year-old children.

Microbiome and its impact on gastrointestinal atopy

The prevalence of allergic conditions has continuously increased in the last few decades in Westernized countries. A dysbiotic gut microbiome may play an important role in the development of allergic diseases. Genetic, environmental, and dietary factors may alter the commensal microbiota leading to inflammatory dysregulation of homeostasis. Murine and human studies have begun to elucidate the role of the microbiota in the pathogenesis of atopic diseases including asthma, atopic dermatitis, and food allergies. However, the role of the microbiome in most eosinophilic gastrointestinal diseases (EGIDs) is not yet known. This review provides an overview of what is currently known about the development of tolerance from both molecular and clinical standpoints. We also look at the gut-specific microbiome and its role in atopic conditions with the hope of applying this knowledge to the understanding, prevention, and treatment of EGIDs, particularly EoE.

Neonatal Gastrointestinal and Respiratory Microbiome in Cystic Fibrosis: Potential Interactions and Implications for Systemic Health

PURPOSE

The gastrointestinal microbiome plays a critical role in nutrition and metabolic and immune functions in infants and young children and has implications for lifelong health. Cystic fibrosis (CF) transmembrane conductance regulator (CFTR) mutations in CF result in viscous mucous production, frequent exposure to antibiotics, and atypical colonization patterns, resulting in an evolving dysbiosis of the gastrointestinal and respiratory microsystems; dysbiosis in CF results in systemic inflammation, chronic infection, and dysregulation of immune function. Dysbiosis in both the respiratory system and gut contributes to undernutrition, growth failure, and long-term respiratory and systemic morbidity in infants and children with CF. Understanding the role that the gut and respiratory microbiome plays in health or disease progression in CF will afford opportunities to better identify interventions to affect clinical changes.

METHODS

Summary was done of the pertinent literature in CF and the study of the microbiome and probiotics.

FINDINGS

New studies have identified bacteria in the respiratory tract in CF that are typically members of the intestinal microbiota, and enteral exposures to breast milk and probiotics are associated with prolonged periods of respiratory stability in CF.

IMPLICATIONS

Understanding the complex interactions between the CFTR mutations, microbial colonization, and mucosal and systemic immunity is of major importance to inform new treatment strategies (such as restoring a healthier microbiome with probiotics or dietary interventions) to improve nutritional status and immune competence and to decrease morbidity and mortality in CF.

Prenatal antibiotic use and risk of childhood wheeze/asthma: A meta-analysis

BACKGROUND

Existing body of knowledge suggests that antibiotic use during pregnancy was inconsistently associated with childhood wheeze/asthma. The aim of this study was to determine whether exposure to antibiotic during pregnancy could increase the risk for childhood wheeze/asthma using a comprehensive meta-analysis.

METHODS

PubMed, MEDLINE, and China National Knowledge Infrastructure (CNKI) were systematically searched for studies up to September 10, 2014, and additional studies were found by searching reference lists of relevant articles. For this meta-analysis, cohort studies and case-control studies assessing the association between antibiotic use during pregnancy and risk of childhood wheeze/asthma were included. Extracted data were mainly pooled using random-effects model. Study quality was assessed using the Newcastle-Ottawa Quality Assessment Scale (NOS).

RESULTS

Ten studies were identified in final analysis. Pooling analysis of these studies showed an OR of 1.20 (95% CI, 1.13-1.27) for wheeze/asthma. After excluding case-control studies and prospective studies without achieving high scores on the NOS, the pooled OR was 1.18 (95% CI, 1.11-1.26). We found the risk of antibiotic use and pooled ORs of wheeze/asthma were 1.09 (95% CI, 0.92-1.29) for the first trimester, 1.14 (95% CI, 1.01-1.29) for the second trimester, and 1.33 (95% CI, 1.11-1.60) for the third trimester, respectively.

CONCLUSIONS

This meta-analysis suggests that antibiotic exposure during pregnancy may increase the risk of wheeze/asthma in childhood. Besides, the risk of developing wheeze/asthma in childhood was marked during last two trimesters of pregnancy. Future studies of large-size and prospective cohorts which adequately address concerns for confounder bias are needed to examine the relationship between antibiotic use and risk of childhood asthma.

Airway microbiota and acute respiratory infection in children

Acute respiratory infections (ARIs), such as bronchiolitis and pneumonia, are the leading cause of hospitalization of infants in the US. While the incidence and severity of ARI can vary widely among children, the reasons for these differences are not fully explained by traditional risk factors (e.g., prematurity, viral pathogens). The recent advent of molecular diagnostic techniques has revealed the presence of highly functional communities of microbes inhabiting the human body (i.e., microbiota) that appear to influence development of local and systemic immune response. We propose a 'risk and resilience' model in which airway microbiota are associated with an increased (risk microbiota) or decreased (resilience microbiota) incidence and severity of ARI in children. We also propose that modulating airway microbiota (e.g., from risk to resilience microbiota) during early childhood will optimize airway immunity and, thereby, decrease ARI incidence and severity in children.

Association Between Antibiotic Exposure, Bronchiolitis, and TLR4 (rs1927911) Polymorphisms in Childhood Asthma

Purpose

The complex interplay between environmental and genetic factors plays an important role in the development of asthma. Several studies have yielded conflicting results regarding the 2 asthma-related risk factors: antibiotic usage during infancy and/or a history of bronchiolitis during early life and the development of asthma. In addition to these risk factors, we also explored the effects of Toll-like receptor 4 (TLR4) polymorphism on the development of childhood asthma.

Methods

This cross-sectional study involved 7,389 middle school students who were from 8 areas of Seoul, Korea, and completed the International Study of Asthma and Allergies in Childhood questionnaire. The TLR4 polymorphism rs1927911 was genotyped in 1,395 middle school students from two areas using the TaqMan assay.

Results

Bronchiolitis in the first 2 years of life, antibiotic exposure during the first year of life, and parental history of asthma were independent risk factors for the development of asthma. When combined, antibiotic use and a history of bronchiolitis increased the risk of asthma (adjusted odds ratio [aOR]: 4.64, 95% confidence interval [CI]: 3.09-6.97, P value for interaction=0.02). In subjects with CC genotype of TLR4, antibiotic exposure and a history of bronchiolitis during infancy, the risk of asthma was increased, compared to subjects without these risk factors (aOR: 5.72, 95% CI: 1.74-18.87).

Conclusions

Early-life antibiotic exposures and a history of bronchiolitis are risk factors for asthma in young adolescents. Polymorphisms of TLR4 modified the influence of these environmental factors. Reducing antibiotic exposure and preventing bronchiolitis during infancy may prevent the development of asthma, especially in genetically susceptible subjects.

Diet and host-microbial crosstalk in postnatal intestinal immune homeostasis

Neonates face unique challenges in the period following birth. The postnatal immune system is in the early stages of development and has a range of functional capabilities that are distinct from the mature adult immune system. Bidirectional immune-microbial interactions regulate the development of mucosal immunity and alter the composition of the microbiota, which contributes to overall host well-being. In the past few years, nutrition has been highlighted as a third element in this interaction that governs host health by modulating microbial composition and the function of the immune system. Dietary changes and imbalances can disturb the immune-microbiota homeostasis, which might alter susceptibility to several autoimmune and metabolic diseases. Major changes in cultural traditions, socioeconomic status and agriculture are affecting the nutritional status of humans worldwide, which is altering core intestinal microbial communities. This phenomenon is especially relevant to the neonatal and paediatric populations, in which the microbiota and immune system are extremely sensitive to dietary influences. In this Review, we discuss the current state of knowledge regarding early-life nutrition, its effects on the microbiota and the consequences of diet-induced perturbation of the structure of the microbial community on mucosal immunity and disease susceptibility.

The central role of the gut microbiota in chronic inflammatory diseases

The commensal microbiota is in constant interaction with the immune system, teaching immune cells to respond to antigens. Studies in mice have demonstrated that manipulation of the intestinal microbiota alters host immune cell homeostasis. Additionally, metagenomic-sequencing analysis has revealed alterations in intestinal microbiota in patients suffering from inflammatory bowel disease, asthma, and obesity. Perturbations in the microbiota composition result in a deficient immune response and impaired tolerance to commensal microorganisms. Due to altered microbiota composition which is associated to some inflammatory diseases, several strategies, such as the administration of probiotics, diet, and antibiotic usage, have been utilized to prevent or ameliorate chronic inflammatory diseases. The purpose of this review is to present and discuss recent evidence showing that the gut microbiota controls immune system function and onset, development, and resolution of some common inflammatory diseases.

The intestinal microbiome in early life: health and disease

Human microbial colonization begins at birth and continues to develop and modulate in species abundance for about 3 years, until the microbiota becomes adult-like. During the same time period, children experience significant developmental changes that influence their health status as well as their immune system. An ever-expanding number of articles associate several diseases with early-life imbalances of the gut microbiota, also referred to as gut microbial dysbiosis. Whether early-life dysbiosis precedes and plays a role in disease pathogenesis, or simply originates from the disease process itself is a question that is beginning to be answered in a few diseases, including IBD, obesity, and asthma. This review describes the gut microbiome structure and function during the formative first years of life, as well as the environmental factors that determine its composition. It also aims to discuss the recent advances in understanding the role of the early-life gut microbiota in the development of immune-mediated, metabolic, and neurological diseases. A greater understanding of how the early-life gut microbiota impacts our immune development could potentially lead to novel microbial-derived therapies that target disease prevention at an early age.

Effect of antibiotic use and mold exposure in infancy on allergic rhinitis in susceptible adolescents

BACKGROUND

Antibiotic use in infancy induces alteration in intestinal microbiota and is associated with the development of allergic diseases. Mold exposure is also associated with allergic diseases. Genetic susceptibility may interact with specific environmental factors in allergic disease development.

OBJECTIVE

To investigate independent and combined effects of antibiotic use and mold exposure in infancy on the risk of allergic rhinitis (AR) in adolescents.

METHODS

Data on AR and environmental factors were collected using the International Study of Asthma and Allergies in Childhood questionnaire from 7,389 adolescents from Seoul, Korea. TaqMan genotyping was performed for interleukin 13 (IL-13) (rs20541) and Toll-like receptor 4 (rs1927911) polymorphisms in 1,395 adolescents.

RESULTS

Age, parental history of AR, antibiotic use in infancy, and pet ownership during pregnancy or infancy were associated with an increased risk of current AR (diagnosis of AR and symptoms of AR within the preceding 12 months). Having older siblings was a protective effect. The adjusted odds ratio (aOR) for current AR for combined antibiotic use and mold exposure in infancy was 1.45 (95% confidence interval [CI], 1.01-2.09). For each factor separately, aORs were 1.25 (95% CI, 1.04-1.50) and 0.99 (95% CI, 0.75-1.31), respectively. Antibiotic and mold exposure in infancy, GA or AA genotypes of IL-13 (rs20541) (aOR 4.53; 95% CI, 1.66-12.38; P for interaction = .05), and CT+TT genotype of Toll-like receptor 4 (rs1927911) (aOR, 3.20; 95% CI, 1.24-8.26; P for interaction = .18) increased the risk of current AR.

CONCLUSION

Antibiotic use and mold exposure in infancy have additive effects on the risk of current AR in genetically susceptible adolescents. Gene-environment interactions between IL-13 (rs20541) and antibiotics or mold may play a role in AR.

Severe viral respiratory infections: are bugs bugging?

Viral respiratory tract infections (RTI) pose a high burden on the youngest members of our society. Several risk factors are known for severe viral respiratory disease. However, a large proportion of the severe RTI cannot be explained by these risk factors. A growing body of evidence shows that the composition of the microbiota has a major influence on the training of both the mucosal and the systemic immune response and can thus potentially determine susceptibility for severe viral infections. In this review, we discuss the current evidence regarding the influence of bacterial colonization on the severity of viral respiratory infections.

A fresh look at the hygiene hypothesis: how intestinal microbial exposure drives immune effector responses in atopic disease

There currently is no consensus on which immunological mechanisms can best explain the rise in atopic disease post industrialization. The hygiene hypothesis lays groundwork for our understanding of how altered microbial exposures can drive atopy; yet since its introduction increasing evidence suggests the exposure of our immune system to the intestinal microbiota plays a key role in development of atopic disease. As societal change shifts our microbial exposure, concordant shifts in the tolerant and effector functions of our immune systems give rise to more hypersensitive responses to external antigens. This is contrasted with the greater immune tolerant capabilities of individuals still living in regions with lifestyles more representative of our evolutionary history. Recent findings, buoyed by technological advances in the field, suggest a direct role for the intestinal microbiota-immune system interplay in the development of atopic disease mechanisms. Overall, harnessing current mechanistic studies for translational research into microbiota composition and function in relation to atopy have potential for the design of therapeutics that could moderate these diseases.

Early life exposure to antibiotics and the risk of childhood allergic diseases: an update from the perspective of the hygiene hypothesis

The prevalence of allergic diseases has been growing rapidly in industrial countries during recent decades. It is postulated that growing up with less microbial exposure may render the immune system susceptible to a T helper type 2 (Th2)-predominant allergic response-also known as the hygiene hypothesis. This review delineates recent epidemiological and experimental evidence for the hygiene hypothesis, and integrates this hypothesis into the association between early life exposure to antibiotics and the development of allergic diseases and asthma. Several retrospective or prospective epidemiological studies reveal that early exposure to antibiotics may be positively associated with the development of allergic diseases and asthma. However, the conclusion is inconsistent. Experimental studies show that antibiotics may induce the Th2-skewed response by suppressing the T helper type 1 (Th1) response through inhibition of Th1 cytokines and disruption of the natural course of infection, or by disturbing the microflora of the gastrointestinal (GI) tract and therefore jeopardizing the establishment of oral tolerance and regulatory T cell immune responses. The hygiene hypothesis may not be the only explanation for the rapid increase in the prevalence of allergic diseases and asthma. Further epidemiological and experimental studies addressing the issue of the impact of environmental factors on the development of allergic diseases and the underlying mechanisms may unveil novel strategies for the prevention and treatment of allergic diseases in the future.

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.

The impact of gut microbes in allergic diseases

PURPOSE OF REVIEW

The prevalence of allergic diseases continues to rise globally in developed countries. Since the initial proposal of the hygiene hypothesis, there has been increasing evidence to suggest that the intestinal microbiota, particularly during early infancy, plays a critical role in regulating immune responses associated with the development of atopy. This review evaluates the key epidemiologic and mechanistic data published to date.

RECENT FINDINGS

Epidemiological data have provided the framework for animal studies investigating the importance of gut commensals in allergy development. These studies provide new insights about the microbial regulation of mucosal immune responses inside and outside the gut, and how these effects may drive allergic inflammation in susceptible individuals. Specific immune cells have been identified as mediators of these microbiota-regulated allergic responses.

SUMMARY

In the last year, technological advances have provided us with a better understanding of the gut microbiome in healthy and allergic individuals. Recent studies have identified the associations between particular gut microbes and different disease phenotypes, as well as identified immune cells and their mediators involved in allergy development. This research has provided a number of host and microbe targets that may be used to develop novel therapies suitable for the treatment or prevention of allergic diseases.

Asthma: a chronic infectious disease?

There are increasing data to support the "hygiene" and "microbiota" hypotheses of a protective role of infections in modulating the risk of subsequent development of asthma. There is less evidence that respiratory infections can actually cause the development of asthma. There is some evidence that rhinovirus respiratory infections are associated with the development of asthma, particularly in childhood, whereas these infections in later life seem to have a weaker association with the development of asthma. The role of bacterial infections in chronic asthma remains unclear. This article reviews the available evidence indicating that asthma may be considered as a chronic infectious disease.

A microarray analysis of gnotobiotic mice indicating that microbial exposure during the neonatal period plays an essential role in immune system development

BACKGROUND

Epidemiological studies have suggested that the encounter with commensal microorganisms during the neonatal period is essential for normal development of the host immune system. Basic research involving gnotobiotic mice has demonstrated that colonization at the age of 5 weeks is too late to reconstitute normal immune function. In this study, we examined the transcriptome profiles of the large intestine (LI), small intestine (SI), liver (LIV), and spleen (SPL) of 3 bacterial colonization models-specific pathogen-free mice (SPF), ex-germ-free mice with bacterial reconstitution at the time of delivery (0WexGF), and ex-germ-free mice with bacterial reconstitution at 5 weeks of age (5WexGF)-and compared them with those of germ-free (GF) mice.

RESULTS

Hundreds of genes were affected in all tissues in each of the colonized models; however, a gene set enrichment analysis method, MetaGene Profiler (MGP), demonstrated that the specific changes of Gene Ontology (GO) categories occurred predominantly in 0WexGF LI, SPF SI, and 5WexGF SPL, respectively. MGP analysis on signal pathways revealed prominent changes in toll-like receptor (TLR)- and type 1 interferon (IFN)-signaling in LI of 0WexGF and SPF mice, but not 5WexGF mice, while 5WexGF mice showed specific changes in chemokine signaling. RT-PCR analysis of TLR-related genes showed that the expression of interferon regulatory factor 3 (Irf3), a crucial rate-limiting transcription factor in the induction of type 1 IFN, prominently decreased in 0WexGF and SPF mice but not in 5WexGF and GF mice.

CONCLUSION

The present study provides important new information regarding the molecular mechanisms of the so-called "hygiene hypothesis".

Early life antibiotic-driven changes in microbiota enhance susceptibility to allergic asthma

Allergic asthma rates have increased steadily in developed countries, arguing for an environmental aetiology. To assess the influence of gut microbiota on experimental murine allergic asthma, we treated neonatal mice with clinical doses of two widely used antibiotics--streptomycin and vancomycin--and evaluated resulting shifts in resident flora and subsequent susceptibility to allergic asthma. Streptomycin treatment had little effect on the microbiota and on disease, whereas vancomycin reduced microbial diversity, shifted the composition of the bacterial population and enhanced disease severity. Neither antibiotic had a significant effect when administered to adult mice. Consistent with the 'hygiene hypothesis', our data support a neonatal, microbiota-driven, specific increase in susceptibility to experimental murine allergic asthma.