Influence of maternal bifidobacteria on the establishment of bifidobacteria colonizing the gut in infants

Transmission and Persistence of Infant Gut-Associated Bifidobacteria

Bifidobacterium infantis are the primary colonizers of the infant gut, yet scientific research addressing the transmission of the genus Bifidobacterium to infants remains incomplete. This review examines microbial reservoirs of infant-type Bifidobacterium that potentially contribute to infant gut colonization. Accordingly, strain inheritance from mother to infant via the fecal-oral route is likely contingent on the bifidobacterial strain and phenotype, whereas transmission via the vaginal microbiota may be restricted to Bifidobacterium breve. Additional reservoirs include breastmilk, horizontal transfer from the environment, and potentially in utero transfer. Given that diet is a strong predictor of Bifidobacterium colonization in early life and the absence of Bifidobacterium is observed regardless of breastfeeding, it is likely that additional factors are responsible for bifidobacterial colonization early in life.

Genomic and ecological approaches to identify the Bifidobacterium breve prototype of the healthy human gut microbiota

Members of the genus Bifidobacterium are among the first microorganisms colonizing the human gut. Among these species, strains of Bifidobacterium breve are known to be commonly transmitted from mother to her newborn, while this species has also been linked with activities supporting human wellbeing. In the current study, an in silico approach, guided by ecology- and phylogenome-based analyses, was employed to identify a representative strain of B. breve to be exploited as a novel health-promoting candidate. The selected strain, i.e., B. breve PRL2012, was found to well represent the genetic content and functional genomic features of the B. breve taxon. We evaluated the ability of PRL2012 to survive in the gastrointestinal tract and to interact with other human gut commensal microbes. When co-cultivated with various human gut commensals, B. breve PRL2012 revealed an enhancement of its metabolic activity coupled with the activation of cellular defense mechanisms to apparently improve its survivability in a simulated ecosystem resembling the human microbiome.

Impact of Gut Microbiota on Host Aggression: Potential Applications for Therapeutic Interventions Early in Development

Aggression in the animal kingdom is a necessary component of life; however, certain forms of aggression, especially in humans, are pathological behaviors that are detrimental to society. Animal models have been used to study a number of factors, including brain morphology, neuropeptides, alcohol consumption, and early life circumstances, to unravel the mechanisms underlying aggression. These animal models have shown validity as experimental models. Moreover, recent studies using mouse, dog, hamster, and drosophila models have indicated that aggression may be affected by the "microbiota-gut-brain axis." Disturbing the gut microbiota of pregnant animals increases aggression in their offspring. In addition, behavioral analyses using germ-free mice have shown that manipulating the intestinal microbiota during early development suppresses aggression. These studies suggest that treating the host gut microbiota during early development is critical. However, few clinical studies have investigated gut-microbiota-targeted treatments with aggression as a primary endpoint. This review aims to clarify the effects of gut microbiota on aggression and discusses the therapeutic potential of regulating human aggression by intervening in gut microbiota.

Evaluation of the factors affecting lung function in pediatric patients with asthma

PURPOSE

This study aimed to analyze the risk factors affecting lung function in children with asthma based on clinical data to advice on clinical treatment and prognosis.

METHODS

This study included newly diagnosed patients with asthma admitted to the Respiratory Department of Chengdu Women's and Children's Central Hospital in Sichuan from July 2020 to June 2021. The factors associated with lung function were analyzed using univariate and multivariate linear regression with the forward method, while factors affecting lung ventilation function were analyzed using multivariate logistic regression.

RESULTS

Sixty percent of the patients had normal lung function. Age was significantly negatively correlated with forced vital capacity (FVC)/FVC_predicted (B = -1.385, p = 0.001), FEV₁/FEV_1predicted (B = -2.092, p < 0.001), and FEV₁%/FEV₁%_predicted (B = -0.834, p = 0.001). Body mass index (BMI) for age Z score (B = 1.661, p = 0.045) and cesarean delivery (B = 4.471, p = 0.013) were significantly positively correlated with FVC/FVC_predicted. Birth weight was significantly positively correlated with FEV₁/FEV_1predicted (B = 4.593, p = 0.027). Multivariate logistic regression analysis revealed that age ≥6 years and cough variant asthma (CVA) were risk factors for abnormal lung function.

CONCLUSIONS

Age, BMI for age Z score, mode of delivery, and birth weight were significantly correlated with lung function in children with asthma. Furthermore, children with asthma and normal lung function were more likely to be overlooked. More attention should be given to children with asthma and normal lung function, and CVA.

In Vitro Infant Fecal Fermentation Characteristics of Human Milk Oligosaccharides Were Controlled by Initial Microbiota Composition More than Chemical Structure

SCOPE

Human milk oligosaccharides (HMOs), multifunctional glycans naturally present in human milk, are known to contribute to the infant's microbiota and immune system development. However, the molecular specificity of HMOs on microbiota and associated fermentation is not yet fully understood, and is important for the development of infant formula optimum functionality.

METHODS AND RESULTS

In vitro fermentation is carried out on structurally different HMOs with infant fecal inocula dominated by Bifidobacterium longum, Bifidobacterium breve, and Bacteroides. The gas, metabolite (SCFA, lactate, and succinate) profiles, and microbiota responses differ between individual microbiota inocula patterns regardless of HMO structure. In terms of HMO pairs with same sugar composition but different glycosidic bonds, gas and metabolite profiles are similar with the B. longum- and B. breve-dominated inocula. However, large individual variations are observed with the Bacteroides-dominated inocula. The microbial communities at the end of fermentation are closely related to the initial microbiota composition.

CONCLUSION

The findings demonstrate that short-term in vitro fermentation outcomes largely depend on the initial gut microbiota composition more than the impact of HMO molecular specificity. These results advance the current understanding for the design of personalized infant nutritional solutions and therapies in future.

Role of Bifidobacteria on Infant Health

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

Role of Maternal Infections and Inflammatory Responses on Craniofacial Development

Pregnancy is a tightly regulated immunological state. Mild environmental perturbations can affect the developing fetus significantly. Infections can elicit severe immunological cascades in the mother's body as well as the developing fetus. Maternal infections and resulting inflammatory responses can mediate epigenetic changes in the fetal genome, depending on the developmental stage. The craniofacial development begins at the early stages of embryogenesis. In this review, we will discuss the immunology of pregnancy and its responsive mechanisms on maternal infections. Further, we will also discuss the epigenetic effects of pathogens, their metabolites and resulting inflammatory responses on the fetus with a special focus on craniofacial development. Understanding the pathophysiological mechanisms of infections and dysregulated inflammatory responses during prenatal development could provide better insights into the origins of craniofacial birth defects.

A synbiotic intervention modulates meta-omics signatures of gut redox potential and acidity in elective caesarean born infants

BACKGROUND

The compromised gut microbiome that results from C-section birth has been hypothesized as a risk factor for the development of non-communicable diseases (NCD). In a double-blind randomized controlled study, 153 infants born by elective C-section received an infant formula supplemented with either synbiotic, prebiotics, or unsupplemented from birth until 4 months old. Vaginally born infants were included as a reference group. Stool samples were collected from day 3 till week 22. Multi-omics were deployed to investigate the impact of mode of delivery and nutrition on the development of the infant gut microbiome, and uncover putative biological mechanisms underlying the role of a compromised microbiome as a risk factor for NCD.

RESULTS

As early as day 3, infants born vaginally presented a hypoxic and acidic gut environment characterized by an enrichment of strict anaerobes (Bifidobacteriaceae). Infants born by C-section presented the hallmark of a compromised microbiome driven by an enrichment of Enterobacteriaceae. This was associated with meta-omics signatures characteristic of a microbiome adapted to a more oxygen-rich gut environment, enriched with genes associated with reactive oxygen species metabolism and lipopolysaccharide biosynthesis, and depleted in genes involved in the metabolism of milk carbohydrates. The synbiotic formula modulated expression of microbial genes involved in (oligo)saccharide metabolism, which emulates the eco-physiological gut environment observed in vaginally born infants. The resulting hypoxic and acidic milieu prevented the establishment of a compromised microbiome.

CONCLUSIONS

This study deciphers the putative functional hallmarks of a compromised microbiome acquired during C-section birth, and the impact of nutrition that may counteract disturbed microbiome development.

TRIAL REGISTRATION

The study was registered in the Dutch Trial Register (Number: 2838 ) on 4th April 2011.

Administration of β-lactam antibiotics and delivery method correlate with intestinal abundances of Bifidobacteria and Bacteroides in early infancy, in Japan

The intestinal microbiome changes dynamically in early infancy. Colonisation by Bifidobacterium and Bacteroides and development of intestinal immunity is interconnected. We performed a prospective observational cohort study to determine the influence of antibiotics taken by the mother immediately before delivery on the intestinal microbiome of 130 healthy Japanese infants. Faecal samples (383) were collected at 1, 3, and 6 months and analysed using next-generation sequencing. Cefazolin was administered before caesarean sections, whereas ampicillin was administered in cases with premature rupture of the membranes and in Group B Streptococcus-positive cases. Bifidobacterium and Bacteroides were dominant (60–70% mean combined occupancy) at all ages. A low abundance of Bifidobacterium was observed in infants exposed to antibiotics at delivery and at 1 and 3 months, with no difference between delivery methods. A lower abundance of Bacteroides was observed after caesarean section than vaginal delivery, irrespective of antibiotic exposure. Additionally, occupancy by Bifidobacterium at 1 and 3 months and by Bacteroides at 3 months differed between infants with and without siblings. All these differences disappeared at 6 months. Infants exposed to intrapartum antibiotics displayed altered Bifidobacterium abundance, whereas abundance of Bacteroides was largely associated with the delivery method. Existence of siblings also significantly influenced the microbiota composition of infants.

Butyrate Levels in the Transition from an Infant- to an Adult-Like Gut Microbiota Correlate with Bacterial Networks Associated with Eubacterium Rectale and Ruminococcus Gnavus

Relatively little is known about the ecological forces shaping the gut microbiota composition during infancy. Therefore, the objective of the present study was to identify the nutrient utilization- and short-chain fatty acid (SCFA) production potential of gut microbes in infants during the first year of life. Stool samples were obtained from mothers at 18 weeks of pregnancy and from infants at birth (first stool) at 3, 6, and 12-months of age from the general population-based PreventADALL cohort. We identified the taxonomic and SCFA composition in 100 mother-child pairs. The SCFA production and substrate utilization potential of gut microbes were observed by multiomics (shotgun sequencing and proteomics) on six infants. We found a four-fold increase in relative butyrate levels from 6 to 12 months of infant age. The increase was correlated to Eubacterium rectale and its bacterial network, and Faecalibacterium prausnitzii relative abundance, while low butyrate at 12 months was correlated to Ruminococcus gnavus and its associated network of bacteria. Both E. rectale and F. prausnitzii expressed enzymes needed for butyrate production and enzymes related to dietary fiber degradation, while R. gnavus expressed mucus-, fucose, and human milk oligosaccharides (HMO)-related degradation enzymes. Therefore, we believe that the presence of E. rectale, its network, and F. prausnitzii are key bacteria in the transition from an infant- to an adult-like gut microbiota with respect to butyrate production. Our results indicate that the transition from an infant- to an adult-like gut microbiota with respect to butyrate producing bacteria, occurs between 6 and 12 months of infant age. The bacteria associated with the increased butyrate ratio/levels were E. rectale and F. prausnitzii, which potentially utilize a variety of dietary fibers based on the glycoside hydrolases (GHs) expressed. R. gnavus with a negative association to butyrate potentially utilizes mucin, fucose, and HMO components. This knowledge could have future importance in understanding how microbial metabolites can impact infant health and development.

Meta-analysis found that studies may have overestimated Caesarean section risks for attention-deficit hyperactivity disorder by ignoring confounding factors

AIM

Epidemiological studies on associations between Caesarean sections (C-sections) and attention-deficit hyperactivity disorder (ADHD) have been inconsistent, and we performed a meta-analysis.

METHODS

We systematically searched PubMed and Embase to December 2018 and included nine hospital-based and population registry studies published in 2011-2018. These covered a total study cohort of more than 2.5 million people in eight countries: Australia, Brazil, Denmark, Finland, Germany, Sweden, Turkey and the UK. The analysis provided summary odds ratios (ORs) and 95% confidence intervals (CI) while taking heterogeneity into account.

RESULTS

We found that that C-sections were associated with a small increase in the risk of ADHD (OR 1.14, 95% CI 1.11, 1.17, I² 0%) in offspring. In subgroup analyses, the association remained for both infants born after elective C-sections (OR, 1.15, 1.11, 1.19, I² 0%) and emergency C-sections (OR, 1.13, 1.1, 1.17, I² 45.4%). However, these were only marginally significant when we pooled data from siblings from other pregnancies (OR, 1.06, 1.00-1.13, I² 0%), implying that the association was due to confounding.

CONCLUSION

The statistically significant association between C-sections and ADHD in children can be partially explained by unmeasured confounding. Further research controlling for important confounders is required before firm conclusions can be drawn.

Prospects for primary prevention of type 1 diabetes by restoring a disappearing microbe

Prevention of childhood-onset type 1 diabetes has become more urgent with its marked increased incidence in recent decades in the modern world. Temporally associated with the rising incidence of type 1 diabetes, as well as other autoimmune and allergic diseases in childhood in modern times, is the disappearance of Bifidobacterium and specifically Bifidobacterium longum subsp. infantis (B. infantis) predominance in the intestinal microbiota of breastfed, vaginally-delivered infants. B. infantis efficiently metabolizes human milk oligosaccharides (HMOs) without cross-feeding free sugar monomers to other commensals or pathogens and thereby dominates the intestinal microbiota of breastfed infants. Increased levels of short-chain fatty acids (SCFA), which stimulate both immunoregulation and healthy intestinal and pancreatic β-cell function, are generated by B. infantis. Based on recent observations of the intestinal microbiota in early life in young children who develop type 1 diabetes and demonstration of the robust preventive effects of SCFA in animal models of autoimmune diabetes, we hypothesize that restoring a B. infantis-dominant microbiota early in infancy will prevent islet autoimmunity and childhood-onset type 1 diabetes.

Bifidobacterial strains in the intestines of newborns originate from their mothers

The gastrointestinal tract is believed to be colonized rapidly with bacteria immediately from birth. The source of these intestinal microbes is an ongoing topic of interest because increasing evidence suggests that the composition of the initial intestinal bacterial colonization strongly affects health. In particular, the source of bifidobacteria has received marked attention because these bacteria are suggested to play a crucial role in protecting against susceptibility to diverse diseases later in life. However, the source of these microbes has remained unclear. Recently, it was confirmed that mothers transmit their unique bifidobacterial strains to their children shortly after birth. The transmitted strains predominate during early infancy, suggesting that maternal intestinal bifidobacteria are an important source of the infant gut microbiota. Accordingly, maintenance of a healthy, balanced gut microbiota during pregnancy has an important positive influence on the newborn gut microbiota.

Potential Impact of Metabolic and Gut Microbial Response to Pregnancy and Lactation in Lean and Diet-Induced Obese Rats on Offspring Obesity Risk

SCOPE

Maternal obesity programs metabolic dysfunction in offspring, increasing their susceptibility to obesity and metabolic diseases in later life. Moreover, pregnancy and lactation are associated with many metabolic adaptations, yet it is unclear how diet-induced maternal obesity may interrupt these processes.

METHODS AND RESULTS

¹ H NMR serum metabolomics analysis was performed on samples collected pre-pregnancy and in pregnant and lactating lean and high fat/sucrose (HFS) diet-induced obese Sprague-Dawley rats to identify maternal metabolic pathways associated with developmental programming of offspring obesity. Gut microbial composition was assessed using qPCR. Offspring of HFS dams had nearly 40% higher adiposity at weaning compared to offspring of lean dams. While pregnancy and lactation were associated with distinct maternal metabolic changes common to both lean and obese dams, we identified several metabolic differences, potentially implicating dysregulated one-carbon and mammary gland metabolism in the metabolic programming of obesity. Gut microbial composition was significantly altered with obesity, and both gestation and lactation were accompanied by changes in gut microbiota.

CONCLUSION

Diet-induced maternal obesity and consumption of an obesogenic maternal diet results in differential metabolic and gut microbial adaptations to pregnancy and lactation; these maladaptations may be directly involved in maternal programming of offspring susceptibility to obesity.

Genomic diversity and distribution of Bifidobacterium longum subsp. longum across the human lifespan

Bifidobacterium longum subsp. longum represents one of the most prevalent bifidobacterial species in the infant, adult and elderly (human) gut. In the current study, we performed a comparative genome analysis involving 145 B. longum representatives, including 113 B. longum subsp. longum strains obtained from healthy Japanese subjects aged between 0 and 98 years. Although MCL clustering did not reveal any correlation between isolated strains and subject age, certain characteristics appear to be more prevalent among strains corresponding to specific host ages, such as genes involved in carbohydrate metabolism and environmental response. Remarkably, a substantial number of strains appeared to have been transmitted across family members, a phenomenon that was shown not to be confined to mother-infant pairs. This suggests that the ubiquitous distribution of B. longum subsp. longum across the human lifespan is at least partly due to extensive transmission between relatives. Our findings form a foundation for future research aimed at unraveling the mechanisms that allow B. longum strains to successfully transfer between human hosts, where they then colonize and persist in the gut environment throughout the host's lifespan.

Maternal antimicrobial use at delivery has a stronger impact than mode of delivery on bifidobacterial colonization in infants: a pilot study

OBJECTIVE

To investigate factors related to bifidobacterial colonization in early infancy, with a focus on maternal antimicrobial use at delivery.

STUDY DESIGN

A cross-sectional pilot study was performed. Feces samples of 33 Japanese healthy infants were collected over 10 months and analyzed by next-generation sequencing to examine the diversity and abundance of the gut microbiota.

RESULTS

The beta diversity index of the gut microbiota differed significantly based on maternal antimicrobial use at delivery (P < 0.05). The most dominant genus was bifidobacteria, and the relative abundance of bifidobacteria in infants exposed to maternal antibiotics was significantly lower than in those who were not exposed (P < 0.05). In contrast, the delivery mode showed no significant relationship with gut microbiota diversity.

CONCLUSIONS

Maternal antimicrobial use at delivery has a stronger effect than delivery mode on the gut microbiota, especially for colonization of bifidobacteria.

Evolution of gut Bifidobacterium population in healthy Japanese infants over the first three years of life: a quantitative assessment

Bifidobacteria are important members of human gut microbiota; however, quantitative data on their early-life dynamics is limited. Here, using a sensitive reverse transcription-qPCR approach, we demonstrate the carriage of eight signature infant-associated Bifidobacterium species (B. longum, B. breve, B. bifidum, B. catenulatum group, B. infantis, B. adolescentis, B. angulatum and B. dentium) in 76 healthy full-term vaginally-born infants from first day to three years of life. About 21% babies carry bifidobacteria at first day of life (6.2 ± 1.9 log₁₀ cells/g feces); and this carriage increases to 64% (8.0 ± 2.2), 79% (8.5 ± 2.1), 97% (9.3 ± 1.8), 99% (9.6 ± 1.6), and 100% (9.7 ± 0.9) at age 7 days, 1, 3 and 6 months, and 3 years, respectively. B. longum, B. breve, B. catenulatum group and B. bifidum are among the earliest and abundant bifidobacterial clades. Interestingly, infants starting formula-feed as early as first week of life have higher bifidobacterial carriage compared to exclusively breast-fed counterparts. Bifidobacteria demonstrate an antagonistic correlation with enterobacteria and enterococci. Further analyses also reveal a relatively lower/ delayed bifidobacterial carriage in cesarean-born babies. The study presents a quantitative perspective of the early-life gut Bifidobacterium colonization and shows how factors such as birth and feeding modes could influence this acquisition even in healthy infants.

The influence of maternal vaginal flora on the intestinal colonization in newborns and 3-month-old infants

AIM

The role of maternal vaginal bacteria on the colonization of neonatal gut is still a matter of discussion. Our aim was to estimate the role of maternal vaginal flora on the development of intestinal flora in neonates and 3-month-old infants.

METHODS

Seventy-nine maternal-neonatal pairs were included in the study. Vaginal swabs were taken before the rupture of membranes after admission to the delivery ward. First neonatal stool (meconium) and stool at 3-month-old infants were collected and cultured. All samples were subjected to microbiological analysis for Streptococcus, Staphylococcus, Bifidobacterium, Clostridium (including C. difficile), Lactobacillus, Escherichia coli, Klebsiella pneumoniae, and Candida.

RESULTS

Maternal vagina was colonized mainly by streptococci (67%) followed by lactobacilli (58%) and Candida spp. (39%). Vaginal streptococci influenced the intestinal colonization in infants with staphylococci, C. difficile, and candida.

CONCLUSION

Vaginal lactobacilli influenced colonization with C. difficile, and Candida. Vaginal flora is a potent factor influencing the development of bacterial flora in the neonatal and infantile gut. The extension of the observation period until 3 months of life allow to discover the potential changes in the intestinal flora of children.

Maternal Prebiotic Ingestion Increased the Number of Fecal Bifidobacteria in Pregnant Women but Not in Their Neonates Aged One Month

Fructooligosaccharides (FOS) can selectively stimulate the growth of bifidobacteria. Here, we investigated the effect of maternal FOS ingestion on maternal and neonatal gut bifidobacteria. In a randomized, double-blind, placebo-controlled study, we administered 8 g/day of FOS or sucrose to 84 women from the 26th week of gestation to one month after delivery. The bifidobacteria count was detected using quantitative PCR in maternal (26 and 36 weeks of gestation) and neonatal (one month after delivery) stools. Maternal stool frequency was recorded from 24 to 36 weeks of gestation. The number of fecal Bifidobacterium spp. and Bifidobacterium longum in the FOS group was significantly higher than that in the placebo group at 36 weeks of gestation (2.7 × 10¹⁰/g vs. 1.1 × 10¹⁰/g and 2.3 × 10¹⁰/g vs. 9.7 × 10⁹/g). In their neonates, these numbers did not differ between the groups. Also, stool frequency in the FOS group was slightly higher than that in the placebo group two weeks after the intervention (1.0 vs. 0.8 times/day), suggesting a potential constipation alleviation effect. In conclusion, the maternal FOS ingestion showed a bifidogenic effect in pregnant women but not in their neonates.

Early gut colonization by Bifidobacterium breve and B. catenulatum differentially modulates eczema risk in children at high risk of developing allergic disease

BACKGROUND

An altered compositional signature and reduced diversity of early gut microbiota are linked to development of allergic disease. We investigated the relationship between dominant Bifidobacterium species during the early post-natal period and subsequent development of allergic disease in the first year of life.

METHODS

Faecal samples were collected at age 1 week, 1 month and 3 months from 117 infants at high risk of allergic disease. Bifidobacterium species were analysed by quantitative PCR and terminal restriction fragment length polymorphism. Infants were examined at 3, 6 and 12 months, and skin prick test was performed at 12 months. Eczema was diagnosed according to the UK Working Party criteria.

RESULTS

The presence of B. catenulatum at 3 months was associated with a higher risk of developing eczema (OR_adj = 4.5; 95% CI: 1.56-13.05, p_adj = 0.005). Infants colonized with B. breve at 1 week (OR_adj = 0.29; 95% CI: 0.09-0.95, p_adj = 0.04) and 3 months (OR_adj = 0.15; 95% CI: 0.05-0.44, p_adj = 0.00001) had a reduced risk of developing eczema. Furthermore, the presence of B. breve at 3 months was associated with a lower risk of atopic sensitization at 12 months (OR_adj = 0.38; 95% CI: 0.15-0.98, p_adj = 0.05). B. breve colonization patterns were influenced by maternal allergic status, household pets and number of siblings.

CONCLUSIONS

Temporal variations in Bifidobacterium colonization patterns early in life are associated with later development of eczema and/or atopic sensitization in infants at high risk of allergic disease. Modulation of the early microbiota may provide a means to prevent eczema in high-risk infants.

Can Probiotics Reduce Diarrhea and Infant Mortality in Africa?: The Project of a Pilot Study

BACKGROUND

Diarrhea accounts for 9% of the mortality among children under 5 years of age worldwide, and it is significantly associated with malnutrition. Each year, diarrhea kills around 760,000 children under 5 years of age and most of these are in sub-Saharan Africa.In Uganda, the infant mortality rate of 58 per 1000 is unacceptably high, and the major contributors include malnutrition, diarrhea, pneumonia, malaria, prematurity, sepsis, and newborn illnesses.There is an urgent need for intervention to prevent and control diarrheal diseases.

STUDY DESIGN

Our open-label, randomized controlled study has the primary endpoint of reducing diarrhea and infectious diseases (number of episodes/severity) and the secondary endpoint of decreasing infant mortality. The trial is currently conducted in Luzira, a suburb of Kampala, the capital of Uganda, and in Gulu and Lira, in the north of Uganda.The study is projected to enroll 4000 babies (control=2000 and treatment=2000) who will be followed till 1 year of life. As controls, 2000 babies of the same community are planned to be considered.The probiotic product selected for the trial is composed of 3 designated microorganisms, namely Bifidobacterium breve BR03 (DSM 16604), B. breve B632 (DSM 24706), and Lactobacillus delbrueckii subsp. delbrueckii LDD01 (DSM 22106). The concentration of the 3 bacteria is 10 viable cells/strain/daily dose (5 drops).

PERSPECTIVES

For a total sample of 4000 babies, the study has an 80% power at a 5% significance level.

Gut Bifidobacteria Populations in Human Health and Aging

The intestinal microbiota has increasingly been shown to have a vital role in various aspects of human health. Indeed, several studies have linked alterations in the gut microbiota with the development of different diseases. Among the vast gut bacterial community, Bifidobacterium is a genus which dominates the intestine of healthy breast-fed infants whereas in adulthood the levels are lower but relatively stable. The presence of different species of bifidobacteria changes with age, from childhood to old age. Bifidobacterium longum, B. breve, and B. bifidum are generally dominant in infants, whereas B. catenulatum, B. adolescentis and, as well as B. longum are more prevalent in adults. Increasingly, evidence is accumulating which shows beneficial effects of supplementation with bifidobacteria for the improvement of human health conditions ranging from protection against infection to different extra- and intra-intestinal positive effects. Moreover, bifidobacteria have been associated with the production of a number of potentially health promoting metabolites including short chain fatty acids, conjugated linoleic acid and bacteriocins. The aim of this mini-review is to describe the bifidobacteria compositional changes associated with different stages in life, highlighting their beneficial role, as well as their presence or absence in many disease states.

Fecal Microbiota and Diet of Children with Chronic Constipation

Many factors explain dysbiosis in chronic constipation (CC), such as a low-fiber diet. The objective of this study was to compare the fecal microbiota of constipated and nonconstipated children and their intake frequencies of food. Methods. This observational study included 79 children (M/F 43/36) aged six to 36 months divided into two groups: cases (39 constipated children) and controls (40 nonconstipated children). We used a structured form to collect demographic variables, conducted anthropometric assessment, and collected food intake frequency data. The fecal microbiota of the stool samples was analyzed by real-time polymerase chain reaction (PCR) using the fluorophore SYBR® Green. Results. Constipated children had a smaller concentration of Lactobacillus per milligram of stool (p = 0.015) than nonconstipated children, but the concentration of Bifidobacterium per milligram of stool (p = 0.323) and the intake of fruits, vegetables (p = 0.563), and junk food (p = 0.093) of the two groups did not differ. Constipated children consumed more dairy products (0.45 ± 0.8; p > 0.001), were more frequently delivered via caesarean section (69.2%), were weaned earlier (median: 120; 60Q₁–240Q₃), and had a family history of constipation (71.8%). Conclusions. Children with CC have a smaller concentration of Lactobacillus in their stools and consume more dairy products.

Diet-induced changes in maternal gut microbiota and metabolomic profiles influence programming of offspring obesity risk in rats

Maternal obesity and overnutrition during pregnancy and lactation can program an increased risk of obesity in offspring. In this context, improving maternal metabolism may help reduce the intergenerational transmission of obesity. Here we show that, in Sprague-Dawley rats, selectively altering obese maternal gut microbial composition with prebiotic treatment reduces maternal energy intake, decreases gestational weight gain, and prevents increased adiposity in dams and their offspring. Maternal serum metabolomics analysis, along with satiety hormone and gut microbiota analysis, identified maternal metabolic signatures that could be implicated in programming offspring obesity risk and highlighted the potential influence of maternal gut microbiota on maternal and offspring metabolism. In particular, the metabolomic signature of insulin resistance in obese rats normalized when dams consumed the prebiotic. In summary, prebiotic intake during pregnancy and lactation improves maternal metabolism in diet-induced obese rats in a manner that attenuates the detrimental nutritional programming of offspring associated with maternal obesity. Overall, these findings contribute to our understanding of the maternal mechanisms influencing the developmental programming of offspring obesity and provide compelling pre-clinical evidence for a potential strategy to improve maternal and offspring metabolic outcomes in human pregnancy.

The neonatal gut harbours distinct bifidobacterial strains

BACKGROUND

Recent studies have described the bifidobacterial composition of neonates at a species level; however, with advancing technologies we can gain insight into the diversity of the bifidobacterial microbiota residing within the infant gut.

OBJECTIVE

To compare species and strain diversity of culturable bifidobacterial populations in faecal samples obtained from healthy term infants on three different feeding regimes.

STUDY DESIGN

In total, 51 healthy term infants were recruited for this study and divided equally into three different groups (n=17) based on their feeding regime during the first 4 weeks of life. Culturable bifidobacterial populations were analysed at week 1, week 4 and 6 months of age. Isolates were characterised to species level by 16s rRNA-internally transcribed spacer (ITS) gene sequence analysis and to strain level by pulsed field gel electrophoresis (PFGE).

RESULTS

In total,173 bifidobacterial strains were detected across all three groups from 2295 isolates, 42% (72 of 173) of which were detected in the prebiotic-fed group, followed by 30% (52 of 173) and 28% (49 of 173) in the breastfed and non-prebiotic-fed groups, respectively. Surprisingly, only two of the 51 infants harboured an identical bifidobacterial strain which was not present in the other 49 infants. Prebiotic supplementation in the early neonatal period increased the prevalence of Bifidobacterium longum in infants, in addition to promoting strain diversity. B. longum was the dominant species recovered from all three groups during the first 6 months of life, followed by Bifidobacterium breve and Bifidobacterium bifidum.

CONCLUSIONS

This study reveals a hitherto unknown level of diversity at the strain level among bifidobacteria isolated from different infants and the influence prebiotic formula feeding has on the bifidobacterial population.

Impact of maternal bifidobacteria and the mode of delivery on Bifidobacterium microbiota in infants

The aim of this study is to examine the influence of maternal intestinal and vaginal bifidobacteria on the colonisation of bifidobacteria in the gut of infants. Faecal samples from 120 healthy pregnant mothers within 1 month of delivery and from their infants at 1 month of age and 98 vaginal swabs from the mothers at the time of delivery were collected at a maternity hospital in Chiang Mai, Thailand. The faecal and vaginal samples were assayed by real-time PCR assays to detect Bifidobacterium species and to estimate the bifidobacterial copy numbers. After adjusting for the numbers of each Bifidobacterium species, delivery mode, and antibiotic use in infants by the age of 1 month, total counts of bifidobacteria in the mothers' faeces were associated with increased copy numbers of bifidobacteria in the faeces of breastfed infants. A caesarean section was also significantly associated with a decrease in the copy numbers of bifidobacteria in the faeces of infants. No significant correlation was found between the bifidobacterial copies of the vaginal swabs and those of the infants' faeces. The intestinal bifidobacterial status of exclusively breastfed infants was significantly positive affected by vaginal delivery and high bifidobacterial copy numbers in their mothers' gut.

Exploring Vertical Transmission of Bifidobacteria from Mother to Child

Passage through the birth canal and consequent exposure to the mother's microbiota is considered to represent the initiating event for microbial colonization of the gastrointestinal tract of the newborn. However, a precise evaluation of such suspected vertical microbiota transmission has yet to be performed. Here, we evaluated the microbiomes of four sample sets, each consisting of a mother's fecal and milk samples and the corresponding infant's fecal sample, by means of amplicon-based profiling supported by shotgun metagenomics data for two key samples. Notably, targeted genome reconstruction from microbiome data revealed vertical transmission of a Bifidobacterium breve strain and a Bifidobacterium longum subsp. longum strain from mother to infant, a notion confirmed by strain isolation and genome sequencing. Furthermore, PCR analyses targeting unique genes from these two strains highlighted their persistence in the infant gut at 6 months. Thus, this study demonstrates the existence of specific bifidobacterial strains that are common to mother and child and thus indicative of vertical transmission and that are maintained in the infant for at least relatively short time spans.

Gut Catalase-Positive Bacteria Cross-Protect Adjacent Bifidobacteria from Oxidative Stress

Bifidobacteria isolated from infant gut and breast milk exhibited different abilities to grow under microaerobic conditions, alone or in the presence of added catalase. In the present study, we demonstrated that some Bifidobacterium strains unable to grow under microaerobic conditions were cross-protected on solid media from oxidative stress by adjacent colonies of gut catalase-positive Staphylococcus epidermidis or Escherichia coli, but not by a catalase-deficient E. coli. The results of this study support the possible contribution of catalase-positive bacteria to the establishment of certain bifidobacteria in non-anaerobic human niches of the infant gastrointestinal tract or mammary gland.

Bacterial community structure associated with elective cesarean section versus vaginal delivery in Chinese newborns

OBJECTIVES

Increasing attention is being paid to the potential for cesarean birth to influence the taxa of the bacteria that compose the infant intestinal microbiota. The present study characterized the diversity of the intestinal microbiota in newborn infants delivered vaginally (VD) or by cesarean section (CD).

METHODS

A cross-sectional study was performed using fecal specimens collected on days 2 and 4 of postnatal life from 25 VD infants and 16 CD infants. Profiles of the fecal microbiota were analyzed using polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis in combination with 16S ribosomal RNA (rRNA) gene sequencing of the clones corresponding to the degenerating gradient gel electrophoresis (DGGE) bands.

RESULTS

On days 2 and 4 of postnatal life, VD and CD infants did not differ in the richness and evenness of the fecal bacterial community; however, the taxa of the fecal microbiota were significantly different between the 2 groups. In VD infants, Escherichia coli, Bacteroides sp, and Bifidobacterium longum were the dominant microbes. In CD infants, Staphylococcus sp, Clostridium sp, Enterobacter sp, and Streptococcus sp were more common.

CONCLUSIONS

These results demonstrate that delivery method has a profound influence on the structure of the intestinal microbiota in Chinese newborn infants. This is in accordance with data reported in other regions.

Amino acid metabolism in intestinal bacteria and its potential implications for mammalian reproduction

Reproduction is vital for producing offspring and preserving genetic resources. However, incidences of many reproductive disorders (e.g. miscarriage, intrauterine growth restriction, premature delivery and lower sperm quality) have either increased dramatically or remained at high rates over the last decades. Mounting evidence shows a strong correlation between enteral protein nutrition and reproduction. Besides serving as major nutrients in the diet, amino acids (AA) are signaling molecules in the regulation of diverse physiological processes, ranging from spermatogenesis to oocyte fertilization and to embryo implantation. Notably, the numbers of bacteria in the intestine exceed the numbers of host cells by 10 times. Microbes in the small-intestinal lumen actively metabolize large amounts of dietary AA and, therefore, affect the entry of AA into the portal circulation for whole-body utilization. Changes in the composition and abundance of AA-metabolizing bacteria in the gut during pregnancy, as well as their translocation to the uterus, may alter uterine function and epigenetic modifications of maternal physiology and metabolism, which are crucial for pregnancy recognition and fetal development. Thus, the presence of the maternal gut microbiota and AA metabolites in the intrauterine environments (e.g. endometrium and placenta) and breast milk is likely a unique signature for the programming of the whole-body microbiome and metabolism in both the fetus and infant. Dietary intervention with functional AA, probiotics and prebiotics to alter the abundance and activity of intestinal bacteria may ameliorate or prevent the development of metabolic syndrome, while improving reproductive performance in both males and females as well as their offspring.

Maternal fucosyltransferase 2 status affects the gut bifidobacterial communities of breastfed infants

BACKGROUND

Individuals with inactive alleles of the fucosyltransferase 2 gene (FUT2; termed the 'secretor' gene) are common in many populations. Some members of the genus Bifidobacterium, common infant gut commensals, are known to consume 2'-fucosylated glycans found in the breast milk of secretor mothers. We investigated the effects of maternal secretor status on the developing infant microbiota with a special emphasis on bifidobacterial species abundance.

RESULTS

On average, bifidobacteria were established earlier and more often in infants fed by secretor mothers than in infants fed by non-secretor mothers. In secretor-fed infants, the relative abundance of the Bifidobacterium longum group was most strongly correlated with high percentages of the order Bifidobacteriales. Conversely, in non-secretor-fed infants, Bifidobacterium breve was positively correlated with Bifidobacteriales, while the B. longum group was negatively correlated. A higher percentage of bifidobacteria isolated from secretor-fed infants consumed 2'-fucosyllactose. Infant feces with high levels of bifidobacteria had lower milk oligosaccharide levels in the feces and higher amounts of lactate. Furthermore, feces containing different bifidobacterial species possessed differing amounts of oligosaccharides, suggesting differential consumption in situ.

CONCLUSIONS

Infants fed by non-secretor mothers are delayed in the establishment of a bifidobacteria-laden microbiota. This delay may be due to difficulties in the infant acquiring a species of bifidobacteria able to consume the specific milk oligosaccharides delivered by the mother. This work provides mechanistic insight into how milk glycans enrich specific beneficial bacterial populations in infants and reveals clues for enhancing enrichment of bifidobacterial populations in at risk populations - such as premature infants.

Mother-to-infant transmission of intestinal bifidobacterial strains has an impact on the early development of vaginally delivered infant's microbiota

Objectives

Bifidobacterium species are one of the major components of the infant's intestine microbiota. Colonization with bifidobacteria in early infancy is suggested to be important for health in later life. However, information remains limited regarding the source of these microbes. Here, we investigated whether specific strains of bifidobacteria in the maternal intestinal flora are transmitted to their infant's intestine.

Materials and Methods

Fecal samples were collected from healthy 17 mother and infant pairs (Vaginal delivery: 12; Cesarean section delivery: 5). Mother's feces were collected twice before delivery. Infant's feces were collected at 0 (meconium), 3, 7, 30, 90 days after birth. Bifidobacteria isolated from feces were genotyped by multilocus sequencing typing, and the transitions of bifidobacteria counts in infant's feces were analyzed by quantitative real-time PCR.

Results

Stains belonging to Bifidobacterium adolescentis, Bifidobacterium bifidum, Bifidobacterium catenulatum, Bifidobacterium longum subsp. longum, and Bifidobacterium pseudocatenulatum, were identified to be monophyletic between mother's and infant's intestine. Eleven out of 12 vaginal delivered infants carried at least one monophyletic strain. The bifidobacterial counts of the species to which the monophyletic strains belong, increased predominantly in the infant's intestine within 3 days after birth. Among infants delivered by C-section, monophyletic strains were not observed. Moreover, the bifidobacterial counts were significantly lower than the vaginal delivered infants until 7 days of age.

Conclusions

Among infants born vaginally, several Bifidobacterium strains transmit from the mother and colonize the infant's intestine shortly after birth. Our data suggest that the mother's intestine is an important source for the vaginal delivered infant's intestinal microbiota.

Functional profiling of the gut microbiome in disease-associated inflammation

The microbial residents of the human gut are a major factor in the development and lifelong maintenance of health. The gut microbiota differs to a large degree from person to person and has an important influence on health and disease due to its interaction with the human immune system. Its overall composition and microbial ecology have been implicated in many autoimmune diseases, and it represents a particularly important area for translational research as a new target for diagnostics and therapeutics in complex inflammatory conditions. Determining the biomolecular mechanisms by which altered microbial communities contribute to human disease will be an important outcome of current functional studies of the human microbiome. In this review, we discuss functional profiling of the human microbiome using metagenomic and metatranscriptomic approaches, focusing on the implications for inflammatory conditions such as inflammatory bowel disease and rheumatoid arthritis. Common themes in gut microbial ecology have emerged among these diverse diseases, but they have not yet been linked to targetable mechanisms such as microbial gene and genome composition, pathway and transcript activity, and metabolism. Combining these microbial activities with host gene, transcript and metabolic information will be necessary to understand how and why these complex interacting systems are altered in disease-associated inflammation.

Variation in consumption of human milk oligosaccharides by infant gut-associated strains of Bifidobacterium breve

Human milk contains a high concentration of complex oligosaccharides that influence the composition of the intestinal microbiota in breast-fed infants. Previous studies have indicated that select species such as Bifidobacterium longum subsp. infantis and Bifidobacterium bifidum can utilize human milk oligosaccharides (HMO) in vitro as the sole carbon source, while the relatively few B. longum subsp. longum and Bifidobacterium breve isolates tested appear less adapted to these substrates. Considering the high frequency at which B. breve is isolated from breast-fed infant feces, we postulated that some B. breve strains can more vigorously consume HMO and thus are enriched in the breast-fed infant gastrointestinal tract. To examine this, a number of B. breve isolates from breast-fed infant feces were characterized for the presence of different glycosyl hydrolases that participate in HMO utilization, as well as by their ability to grow on HMO or specific HMO species such as lacto-N-tetraose (LNT) and fucosyllactose. All B. breve strains showed high levels of growth on LNT and lacto-N-neotetraose (LNnT), and, in general, growth on total HMO was moderate for most of the strains, with several strain differences. Growth and consumption of fucosylated HMO were strain dependent, mostly in isolates possessing a glycosyl hydrolase family 29 α-fucosidase. Glycoprofiling of the spent supernatant after HMO fermentation by select strains revealed that all B. breve strains can utilize sialylated HMO to a certain extent, especially sialyl-lacto-N-tetraose. Interestingly, this specific oligosaccharide was depleted before neutral LNT by strain SC95. In aggregate, this work indicates that the HMO consumption phenotype in B. breve is variable; however, some strains display specific adaptations to these substrates, enabling more vigorous consumption of fucosylated and sialylated HMO. These results provide a rationale for the predominance of this species in breast-fed infant feces and contribute to a more accurate picture of the ecology of the developing infant intestinal microbiota.

Commensal microbiota modulate murine behaviors in a strictly contamination-free environment confirmed by culture-based methods

BACKGROUND

There is increasing evidence suggesting the existence of an interaction between commensal microbiota, the gut and the brain. The aim of this study was to examine the influence of commensal microbiota on the host behaviors in a contamination-free environment, which was verified by culture-based methods.

METHODS

Open-field and marble-burying tests were used to analyze anxiety-like behaviors and locomotor activity in gnotobiotic BALB/c mice with a common genetic background in a sterile isolator. The monoamine levels in several regions of the brain were measured in germfree (GF) mice and commensal fecal microbiota-associated mice (EX-GF).

KEY RESULTS

A 24-h exposure to the environment outside the sterile isolators rendered GF mice less anxious than those not contaminated, while there was no change in the locomotion. EX-GF mice, the gnotobiotic mice with normal specific pathogen-free microbiota, were less anxious and active than GF mice using open-field and marble-burying tests. The norepinephrine, dopamine, and serotonin turnover rates were higher in the EX-GF mice than in the GF mice in most regions of the brain, suggesting that monoaminergic neurotransmission might increase in the EX-GF mice comparing the GF mice. Monoassociation with Brautia coccoides reduced the anxiety level, but it did not affect the locomotor activity. In contrast, colonization with Bifidobacterium infantis decreased the locomotor activity, while having little effect on the anxiety level.

CONCLUSIONS & INFERENCES

These results strongly support the current view that gut microorganisms modulate brain development and behavior.

Ecology and characteristics of methanogenic archaea in animals and humans

In this review, the molecular techniques used in animal-based-methanogen studies will be discussed along with how methanogens interact not only with other microorganisms but with their animal hosts as well. These methods not only indicate the diversity and levels of methanogens, but also provide insight on their ecological functions. Most molecular techniques have been based on either 16S rRNA genes or methyl-coenzyme M reductase, a ubiquitous enzyme in methanogens. The most predominant methanogens in animals belong to the genus Methanobrevibacter. Besides methanogens contributing to overall H2 balance, methanogens also have mutual interactions with other bacteria. In addition to shared metabolic synergism, the host animal retrieves additional energy from the diet when methanogens are co-colonized with other normal flora. By comparing genes in methanogens with other bacteria, possible gene transfer between methanogens and other bacteria in the same environments appears to occur. Finally, diets in conjunction with the genetics of methanogens and hosts may represent the biological framework that dictate the extent of methanogen prevalence in these ecosystems. In addition, host evolution including the immune system could serve as an additional selective pressure for methanogen colonization.

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

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

Maternal intestinal flora and wheeze in early childhood

BACKGROUND

Increasing evidence links altered intestinal flora in infancy to eczema and asthma. No studies have investigated the influence of maternal intestinal flora on wheezing and eczema in early childhood.

OBJECTIVE

To investigate the link between maternal intestinal flora during pregnancy and development of wheeze and eczema in infancy.

METHODS

A total of 60 pregnant women from the Boston area gave stool samples during the third trimester of their pregnancy and answered questions during pregnancy about their own health, and about their children's health when the child was 2 and 6 months of age. Quantitative culture was performed on stool samples and measured in log(10)colony-forming units (CFU)/gram stool. Primary outcomes included infant wheeze and eczema in the first 6 months of life. Atopic wheeze, defined as wheeze and eczema, was analysed as a secondary outcome.

RESULTS

In multivariate models adjusted for breastfeeding, day care attendance and maternal atopy, higher counts of maternal total aerobes (TA) and enterococci (E) were associated with increased risk of infant wheeze (TA: OR 2.32 for 1 log increase in CFU/g stool [95% CI 1.22, 4.42]; E: OR 1.57 [95% CI 1.06, 2.31]). No organisms were associated with either eczema or atopic wheeze.

CONCLUSIONS AND CLINICAL RELEVANCE

In our cohort, higher maternal total aerobes and enterococci were related to increased risk of infant wheeze. Maternal intestinal flora may be an important environmental exposure in early immune system development.

Can nutritional modulation of maternal intestinal microbiota influence the development of the infant gastrointestinal tract?

The gastrointestinal microbiota plays an important role in maintaining host health by preventing the colonization of pathogens, fermenting dietary compounds, and maintaining normal mucosal immunity. Particularly in early life, the composition of the microbiota profoundly influences the development and maturation of the gastrointestinal tract (GIT) mucosa, which may affect health in later life. Therefore, strategies to manipulate the microbiota during infancy may prevent the development of some diseases later in adult life. Earlier research suggested that term fetuses are sterile and that the initial bacterial colonization of the newborn GIT occurs only after the baby transits through the birth canal. However, recent studies have demonstrated that the colonization and/or contact of the fetus with the maternal GIT microbiota may start in utero. After vaginal birth, the colonization of the neonate GIT continues through contact with maternal feces and vaginal bacteria, leading to a relatively simple microbial community that is influenced by feeding type (breast vs. formula feeding). Maternal GIT microbiota, vaginal microbiota, and breast milk composition are influenced by maternal diet. Alterations of the maternal GIT microbiota composition via supplementation with probiotics and prebiotics have been shown; however, transfer of these benefits to the offspring remains to be demonstrated. This review focuses on the influence of maternal GIT microbiota during the pre- and postpartum periods on the colonization of the infant GIT. In particular, it examines the manipulation of the maternal GIT microbiota composition through the use of probiotics and/or prebiotics and subsequent consequences for the health of the offspring.

Influence of maternal bifidobacteria on the development of gut bifidobacteria in infants

Intestinal microbiota plays an important role in human health by influencing metabolic activities that result in the creation of energy and absorbable nutrients, a barrier to the colonization of pathogens, and stimulation of the immune system. The development of fecal microbiota in neonates is crucial because those bacteria are the first to colonize the sterile intestine of the neonates and, thus, have a significant effect on the host. Initial colonization is also relevant to the final composition of the permanent microbiota in adults. Bifidobacteria are predominant in the fecal microbiota of infants, and, therefore, they are important to an understanding of how commensal bifidobacteria is established in the intestine of infants. While the mother's bifidobacteria are considered to significantly influence the infant's bifidobacteria, it is not clear whether a specific bifidobacterial strain transmits vertically from mother to infant and what factors of the mother before delivery influence the establishment of intestinal bifidobacteria in infants. This review focuses on the impact of maternal bifidobacteria on the development of gut bifidobacteria in the infant and suggests that there is cumulative evidence regarding bifidobacterial transfer from the maternal gut or breast milk to the infant gut.

Bacterial colonization and gut development in preterm neonates

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

Transmission of intestinal Bifidobacterium longum subsp. longum strains from mother to infant, determined by multilocus sequencing typing and amplified fragment length polymorphism

The gastrointestinal tracts of neonates are colonized by bacteria immediately after birth. It has been discussed that the intestinal microbiota of neonates includes strains transferred from the mothers. Although some studies have indicated possible bacterial transfer from the mother to the newborn, this is the first report confirming the transfer of bifidobacteria at the strain level. Here, we investigated the mother-to-infant transmission of Bifidobacterium longum subsp. longum by genotyping bacterial isolates from the feces of mothers before delivery and of their infants after delivery. Two hundred seven isolates from 8 pairs of mothers and infants were discriminated by multilocus sequencing typing (MLST) and amplified fragment length polymorphism (AFLP) analysis. By both methods, 11 strains of B. longum subsp. longum were found to be monophyletic for the feces of the mother and her infant. This finding confirms that these strains were transferred from the intestine of the mother to that of the infant. These strains were found in the first feces (meconium) of the infant and in the feces at days 3, 7, 30, and 90 after birth, indicating that they stably colonize the infant's intestine immediately after birth. The strains isolated from each family did not belong to clusters derived from any of the other families, suggesting that each mother-infant pair might have unique family-specific strains.

Role of indigenous lactobacilli in gastrin-mediated acid production in the mouse stomach

It is known that the stomach is colonized by indigenous lactobacilli in mice. The aim of this study was to examine the role of such lactobacilli in the development of the stomach. For a DNA microarray analysis, germ-free BALB/c mice were orally inoculated with 10(9) CFU lactobacilli, and their stomachs were excised after 10 days to extract RNA. As a result, lactobacillus-associated gnotobiotic mice showed dramatically decreased expression of the gastrin gene in comparison to germ-free mice. The mean of the log(2) fold change in the gastrin gene was -4.3. Immunohistochemistry also demonstrated the number of gastrin-positive (gastrin(+)) cells to be significantly lower in the lactobacillus-associated gnotobiotic mice than in the germ-free mice. However, there was no significant difference in the number of somatostatin(+) cells in these groups of mice. Consequently, gastric acid secretion also decreased in the mice colonized by lactobacilli. In addition, an increase in the expression of the genes related to muscle system development, such as nebulin and troponin genes, was observed in lactobacillus-associated mice. Moreover, infection of germ-free mice with Helicobacter pylori also showed the down- and upregulation of gastrin and muscle genes, respectively, in the stomach. These results thus suggested that indigenous lactobacilli in the stomach significantly affect the regulation of gastrin-mediated gastric acid secretion without affecting somatostatin secretion in mice, while H. pylori also exerts such an effect on the stomach.

Comparative analysis of the properties of bifidobacterial isolates from fecal samples of mother-infant pairs

OBJECTIVES

The aim of the study was to evaluate the possibility of Bifidobacterium breve transfer from the mother to her infant during the perinatal period.

MATERIALS AND METHODS

Hundred isolates of B breve and 80 isolates of Bifidobacterium longum were collected from paired fecal samples of mothers and their infants. Bacterial DNA from the samples was comparatively analyzed by random amplification of polymorphic DNA. The growth of the bacteria was examined in vitro.

RESULTS

The analysis of diversity in B breve population showed that infant-derived isolates had significantly less diversity than mother-derived isolates. The analysis of the similarity between these samples revealed that the number of shared type isolates tended to be higher in infants than in their mothers. In the isolates of B longum, however, no such difference was found in the diversity between mother- and infant-derived isolates. Examination of the growth of B breve strains revealed that the shared type strains have a significantly higher growth than nonshared strains both in the presence of galactooligosaccharides and at a higher redox potential.

CONCLUSIONS

These results suggested that subpopulations of B breve strains in the mothers may be transferred to their infants. Such populations may become dominant in the gut of infants at an early time after birth, during which time the transmission of the bifidobacteria of environmental origin is not yet established. B breve strain possessing a higher growth advantage in these conditions may be advantageous for colonization in the infant gut.

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.