Do patients with inflammatory bowel disease really know what other immune-mediated inflammatory diseases they are diagnosed with?

BACKGROUND AND AIMS: The association of inflammatory bowel disease (IBD) with other immune-mediated inflammatory diseases (IMIDs) in the same patient is well known. We aimed to evaluate the degree of knowledge that patients with IBD have regarding the coexistence of other IMIDs and to analyze the factors associated with the concordance between self-reported and confirmed medical information. METHODS: Patients with IBD at a tertiary hospital answered a questionnaire on the presence of 54 IMIDs (self-reported diagnosis), and their IMID diagnosis was confirmed in their medical records (reference diagnosis). Agreement between the self-reported IMID and the IMID according to medical records was evaluated. The association between concordance and different predictors was evaluated using logistic regression models. RESULTS: A total of 1,620 patients were included. Six hundred and twenty-six (39%) patients were diagnosed with at least one IMID, and 177 (11%) with two or more. Overall agreement between patients´ self-report and medical records was k:0.61. When we grouped IMIDs according to affected organs or systems, agreement on rheumatic IMIDs was moderate (k:0.58), whereas agreement on cutaneous (k:0.66), endocrine (k: 0.74) and ocular (k:0.73) IMIDs was substantial. Among patients who had IMIDs, the factor associated with greater concordance was female gender, while lower concordance was associated with a lower educational level and the fact that the IMID had been diagnosed at the same time or later than IBD. CONCLUSION: The knowledge that patients with IBD have regarding the coexistence of other IMIDs is poor, especially in rheumatic IMIDs.

Personalized Nutrition with Banked Human Milk for Early Gut Microbiota Development: In Pursuit of the Perfect Match.

The correct initial colonization and establishment of the gut microbiota during the early stages of life is a key step, with long-lasting consequences throughout the entire lifespan of the individual. This process is affected by several perinatal factors; among them, feeding mode is known to have a critical role. Breastfeeding is the optimal nutrition for neonates; however, it is not always possible, especially in cases of prematurity or early pathology. In such cases, most commonly babies are fed with infant formulas in spite of the official nutritional and health international organizations' recommendation on the use of donated human milk through milk banks for these cases. However, donated human milk still does not totally match maternal milk in terms of infant growth and gut microbiota development. The present review summarizes the practices of milk banks and hospitals regarding donated human milk, its safety and quality, and the health outcomes in infants fed with donated human milk. Additionally, we explore different alternatives to customize pasteurized donated human milk with the aim of finding the perfect match between each baby and banked milk for promoting the establishment of a beneficial gut microbiota from the early stages of life.

Combined Effects of Early Life Stress and Prolonged Exposure to Western Diet on Emotional Responses and Gut Microbiota.

BACKGROUND: Exposure to early life stress (ELS) and maternal consumption of a high-fat and high-sugar diet can have detrimental effects on adult emotional responses. The microbiota and gut-brain axis have been proposed as playing a mediating role in the regulation of stress and emotion. METHOD: Young male rats were exposed to maternal separation (MS) together with maternal and postnatal consumption of a HFS diet (45%kcal saturated fat, 17%kcal sucrose). Anxiety-like behaviour was evaluated using an elevated zero-maze, and depression-like behaviour using the forced-swim and sucrose preference tests. Microbiota composition and derived metabolites were also analysed in faecal samples using a gas chromatograph and mass spectrometry. RESULTS: Combined exposure to MS and lifelong consumption of a HFS diet partially reversed the abnormal anxiety-like and depression-like behaviours in early adulthood caused by each adverse factor alone. Diet composition had a greater negative impact than ELS exposure on the gut microbiota, and both environmental factors interacted with microbiota composition partially counteracting their negative effects. CONCLUSIONS: The effects of exposure to early life stress and a HFS diet independently are partially reversed after the combination of both factors. These results suggest that ELS and diet interact to modulate adult stress response and gut microbiota.

Probiotic-Induced Modulation of Microbiota Composition and Antibiotic Resistance Genes Load, an In Vitro Assessment.

The imbalance of the gut microbiota (GM) is known as dysbiosis and is associated with disorders such as obesity. The increasing prevalence of microorganisms harboring antibiotic resistance genes (ARG) in the GM has been reported as a potential risk for spreading multi-drug-resistant pathogens. The objective of this work was the evaluation, in a fecal culture model, of different probiotics for their ability to modulate GM composition and ARG levels on two population groups, extremely obese (OB) and normal-weight (NW) subjects. Clear differences in the basal microbiota composition were observed between NW and OB donors. The microbial profile assessed by metataxonomics revealed the broader impact of probiotics on the OB microbiota composition. Also, supplementation with probiotics promoted significant reductions in the absolute levels of tetM and tetO genes. Regarding the blaTEM gene, a minor but significant decrease in both donor groups was detected after probiotic addition. A negative association between the abundance of Bifidobacteriaceae and the tetM gene was observed. Our results show the ability of some of the tested strains to modulate GM. Moreover, the results suggest the potential application of probiotics for reducing the levels of ARG, which constitutes an interesting target for the future development of probiotics.

Probiotics for Prevention and Treatment of Clostridium difficile Infection.

Probiotics have been claimed as a valuable tool to restore the balance in the intestinal microbiota following a dysbiosis caused by, among other factors, antibiotic therapy. This perturbed environment could favor the overgrowth of Clostridium difficile, and in fact, the occurrence of C. difficile-associated infections (CDI) is increasing in recent years. In spite of the high number of probiotics able to in vitro inhibit the growth and/or toxicity of this pathogen, its application for treatment or prevention of CDI is still scarce since there are not enough well-defined clinical studies supporting efficacy. Only a few strains, such as Lactobacillus rhamnosus GG and Saccharomyces boulardii, have been studied in more extent. The increasing knowledge about the probiotic mechanisms of action against C. difficile, some of them reviewed here, makes promising the application of these live biotherapeutic agents against CDI. Nevertheless, more effort must be paid to standardize the clinical studies conducted to evaluate probiotic products, in combination with antibiotics, in order to select the best candidate for C. difficile infections.

Assessment trial of the effect of enteral insulin on the preterm infant intestinal microbiota.

BACKGROUND: Insulin might be associated with changes in infant gastrointestinal microbiota. The objective of this randomized controlled trial was to assess the efficacy of two doses of recombinant human(rh) enteral insulin administration compared to placebo in intestinal microbiota. METHODS: 19 preterm patients were recruited at the NICU of La Paz University Hospital (Madrid, Spain). Subjects received 2000 µIU of rh enteral insulin/ml(n = 8), 400 µIU of rh enteral insulin/ml(n = 6) or placebo(n = 5) for 28 days administered once per day. Extracted DNA from fecal samples collected at the beginning and end of treatment were analyzed. The 16S rRNA V4 region was amplified and sequenced in a Miseq(Illumina®) sequencer using 2 × 250 bp paired end. Resulting reads were filtered and analyzed using Qiime2 software. Metabolic activity was assessed by GC. RESULTS: Gestational age and birth weight did not differ between groups. At the phylum level, both insulin treated groups increased the relative abundance of Bacillota, while Pseudomonadota decreased. No change was observed in infants receiving placebo. At the genus level, insulin at both doses showed enriching effects on Clostridium. We found a significant increase in concentrations of fecal propionate in both rh insulin treated groups. CONCLUSION: Rh insulin may modify neonatal intestinal microbiota and SCFAs in preterm infants. IMPACT STATEMENT: Decrease of Pseudomonadota (former Proteobacteria phylum) and increase of Bacillota (former Firmicutes phylum) obtained in this study are the changes observed previously in low-risk infants for NEC. The administration of recombinant enteral insulin may modify the microbiota of preterm new-borns and SCFAs. Modulation of the microbiota may be a mechanism whereby insulin contributes to neonatal intestinal maturation and/or protection.

Combined Effects of Early Life Stress and Prolonged Exposure to Western Diet on Emotional Responses and Gut Microbiota / Efectos Combinados del Estrés Vital Temprano y la Exposición Prolongada a la Dieta Occidental Sobre las Respuestas Emocionales y la Microbiota Intestinal

Background: Exposure to early life stress (ELS) and maternal consumption of a high-fat and high-sugar diet can have detrimental effects on adult emotional responses. The microbiota and gut-brain axis have been proposed as playing a mediating role in the regulation of stress and emotion. Method: Young male rats were exposed to maternal separation (MS) together with maternal and postnatal consumption of a HFS diet (45%kcal saturated fat, 17%kcal sucrose). Anxiety-like behaviour was evaluated using an elevated zero-maze, and depression-like behaviour using the forced-swim and sucrose preference tests. Microbiota composition and derived metabolites were also analysed in faecal samples using a gas chromatograph and mass spectrometry. Results: Combined exposure to MS and lifelong consumption of a HFS diet partially reversed the abnormal anxiety-like and depression-like behaviours in early adulthood caused by each adverse factor alone. Diet composition had a greater negative impact than ELS exposure on the gut microbiota, and both environmental factors interacted with microbiota composition partially counteracting their negative effects. Conclusions: The effects of exposure to early life stress and a HFS diet independently are partially reversed after the combination of both factors. These results suggest that ELS and diet interact to modulate adult stress response and gut microbiota.(AU)

Antecedentes: El estrés temprano (ET) y el consumo materno de una dieta alta en grasas y azúcares (HFS) pueden tener efectos perjudiciales sobre las respuestas emocionales en la adultez. La microbiota y el eje intestino-cerebro podrían mediar la regulación del estrés y las emociones. Método: Ratas macho jóvenes se expusieron a separación materna (SM) y a consumo materno y postnatal de una dieta HFS (45%kcal grasa saturada, 17%kcal sacarosa). Se evaluó el comportamiento ansioso mediante el laberinto cero elevado y el comportamiento depresivo mediante natación forzada y preferencia por sacarosa. Se analizó la microbiota en heces empleando cromatografía de gas y espectrometría de masas. Resultados: La exposición combinada a la SM y el consumo de una dieta HFS revirtió parcialmente la ansiedad y depresión en adultos causadas independientemente por cada factor adverso. La dieta influyó negativamente más que la exposición a ET en la microbiota y ambos factores modificaron su composición contrarrestando parcialmente sus efectos negativos. Conclusiones: Los efectos del ET y una dieta HFS por independiente varían con respecto a los efectos de la combinación de ambos factores, sugiriendo que el ET y la dieta interactúan modulando en el adulto la respuesta al estrés y la microbiota intestinal.(AU)

2-Fucosyllactose Metabolism by Bifidobacteria Promotes Lactobacilli Growth in Co-Culture.

Breastfeeding is recognized as the gold standard in infant nutrition, not only because of breastmilk's intrinsic nutritional benefits but also due to the high content of different bioactive components such as 2-fucosyllactose (2'FL) in the mother's milk. It promotes the growth of its two major consumers, Bifidobacterium longum ssp. infantis and Bifidobacterium bifidum, but the effect on other intestinal microorganisms of infant microbiota remains incompletely understood. pH-uncontrolled fecal cultures from infants donors identified as "fast 2'FL -degrader" microbiota phenotype were used for the isolation of 2'FL-associated microorganisms. The use of specific selective agents allowed the successful isolation of B. bifidum IPLA20048 and of Lactobacillus gasseri IPLA20136. The characterization of 2'FL consumption and its moieties has revealed more pronounced growth, pH drop, and lactic acid production after 2'FL consumption when both microorganisms were grown together. The results point to an association between B. bifidum IPLA20048 and L. gasseri IPLA20136 in which L. gasseri is able to use the galactose from the lactose moiety after the hydrolysis of 2'FL by B. bifidum. The additional screening of two groups of bifidobacteria (n = 38), fast and slow degraders of 2'FL, in co-culture with lactobacilli confirmed a potential cross-feeding mechanism based on degradation products released from bifidobacterial 2'FL break-down. Our work suggests that this phenomenon may be widespread among lactobacilli and bifidobacteria in the infant gut. More investigation is needed to decipher how the ability to degrade 2'FL and other human milk oligosaccharides could influence the microbiota establishment in neonates and the evolution of the microbiota in adult life.

Associations of dietary factors and xenobiotic intake with faecal microbiota composition according to the presence of intestinal mucosa damage.

Diet is a major modulator of gut microbiota, which plays a key role in the health status, including colorectal cancer (CRC) development. Several studies and meta-analyses have evidenced an association of certain dietary factors and xenobiotic intake with the incidence of CRC. Nevertheless, how these dietary factors impact the first stages of intestinal mucosa damage is still uncertain. This study aimed at exploring the associations of relevant dietary factors with the gut microbiota of control individuals and subjects diagnosed with intestinal polyps. A total of 60 volunteers were recruited, clinically classified according to colonoscopy criteria and interviewed using food frequency questionnaires (FFQs). The nutritional status of each volunteer was determined and the intake of dietary xenobiotics was quantified. The relative abundance of faecal microbiota taxonomic groups was obtained through 16S rRNA gene sequencing. The association of dietary factors and xenobiotics with faecal microbiota composition showed differences according to the clinical diagnosis group. Our results showed that the intake of red meat (≥50 g day-1) and total polycyclic aromatic hydrocarbons (PAHs) (≥0.75 µg day-1) was associated with a decreased abundance of the family Bacteroidaceae and an increased abundance of Coriobacteriaceae in control subjects. The intake of the heterocyclic amines 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP) (≥40 ng day-1) and 2-amino-3,8 dimethylimidazo(4,5,f) quinoxaline (MeIQx) (≥50 ng day-1) was associated with a decreased abundance of Akkermansiaceae in the control diagnosis group. Moreover, N-nitroso compounds (NOCs), nitrites (≥1.69 mg day-1) and N-nitrosodimethylamine (NDMA) (≥0.126 µg day-1) were associated with a decreased abundance of Bifidobacteriaceae. The intake of ethanol (≥12 g day-1) in the polyps group was associated with an increased abundance of Peptostreptococcaceae and a decreased abundance of Veillonellaceae. Moreover, linear regression analyses allowed us to identify ethanol, calcium, bioactive compounds such as flavonoids, stilbenes, cellulose, phenolic acids or total polyphenols, and dietary xenobiotics such as PhIP and MeIQx, the NOC N-nitrosopyrrolidine (NPYR) or the total PAHs as potential predictors of faecal microbiota group abundances. These results indicated that the consumption of milk, red meat, processed meat and ethanol and the intake of polyphenols, dietary PAHs, HAs and NOCs are associated with specific groups of the intestinal microbiota, depending on the clinical diagnosis group.

Old Folks, Bad Boon: Antimicrobial Resistance in the Infant Gut Microbiome.

The development of the intestinal microbiome in the neonate starts, mainly, at birth, when the infant receives its founding microbial inoculum from the mother. This microbiome contains genes conferring resistance to antibiotics since these are found in some of the microorganisms present in the intestine. Similarly to microbiota composition, the possession of antibiotic resistance genes is affected by different perinatal factors. Moreover, antibiotics are the most used drugs in early life, and the use of antibiotics in pediatrics covers a wide variety of possibilities and treatment options. The disruption in the early microbiota caused by antibiotics may be of great relevance, not just because it may limit colonization by beneficial microorganisms and increase that of potential pathogens, but also because it may increase the levels of antibiotic resistance genes. The increase in antibiotic-resistant microorganisms is one of the major public health threats that humanity has to face and, therefore, understanding the factors that determine the development of the resistome in early life is of relevance. Recent advancements in sequencing technologies have enabled the study of the microbiota and the resistome at unprecedent levels. These aspects are discussed in this review as well as some potential interventions aimed at reducing the possession of resistance genes.

Impact on Fecal Microbiota and Health-Related Markers of an Intervention Focused on Improving Eating Behavior in People at Risk of Food Insecurity.

Non-communicable diseases are particularly prevalent among low-income individuals and are associated with the consumption of processed foods, fat, and sugars. This work aims to evaluate the impacts of a nutrition education intervention for low socio-economic individuals on sensory perception, health-related parameters and gut microbiota. Twenty low-income adults underwent a 4-week intervention. Dietary information (three 24 h recalls), detection thresholds and discrimination scores (salty and sweet), and severity of depressive symptoms (Beck Depression Inventory-II (BDI-II)) were collected. Fecal microbial composition and short chain fatty acids were determined by 16S ribosomal RNA-gene sequencing and gas chromatography, respectively. After the intervention, 35% of subjects presented higher compliance with dietary recommendations, increased consumption of vegetables and lignans and reduced consumption of processed meats and nitrosamines, together with depleted levels of Actinomycetota. Higher discrimination for salty and sweet and lower BDI-II scores were also obtained. This nutrition education intervention entailed changes in dietary intake towards healthier food options, reduced potentially carcinogenic compounds and improved scores for discrimination and severity of depressive symptoms. The confirmation of these results in future studies would enable the design of strategic policies contributing to the optimal nutrition of materially deprived families through affordable healthy plant-based interventions.

Genetic strategies for sex-biased persistence of gut microbes across human life.

Although compositional variation in the gut microbiome during human development has been extensively investigated, strain-resolved dynamic changes remain to be fully uncovered. In the current study, shotgun metagenomic sequencing data of 12,415 fecal microbiomes from healthy individuals are employed for strain-level tracking of gut microbiota members to elucidate its evolving biodiversity across the human life span. This detailed longitudinal meta-analysis reveals host sex-related persistence of strains belonging to common, maternally-inherited species, such as Bifidobacterium bifidum and Bifidobacterium longum subsp. longum. Comparative genome analyses, coupled with experiments including intimate interaction between microbes and human intestinal cells, show that specific bacterial glycosyl hydrolases related to host-glycan metabolism may contribute to more efficient colonization in females compared to males. These findings point to an intriguing ancient sex-specific host-microbe coevolution driving the selective persistence in women of key microbial taxa that may be vertically passed on to the next generation.

Poststroke Lung Infection by Opportunistic Commensal Bacteria Is Not Mediated by Their Expansion in the Gut Microbiota.

BACKGROUND: Respiratory and urinary tract infections are frequent complications in patients with severe stroke. Stroke-associated infection is mainly due to opportunistic commensal bacteria of the microbiota that may translocate from the gut. We investigated the mechanisms underlying gut dysbiosis and poststroke infection. METHODS: Using a model of transient cerebral ischemia in mice, we explored the relationship between immunometabolic dysregulation, gut barrier dysfunction, gut microbial alterations, and bacterial colonization of organs, and we explored the effect of several drug treatments. RESULTS: Stroke-induced lymphocytopenia and widespread colonization of lung and other organs by opportunistic commensal bacteria. This effect correlated with reduced gut epithelial barrier resistance, and a proinflammatory sway in the gut illustrated by complement and nuclear factor-κB activation, reduced number of gut regulatory T cells, and a shift of gut lymphocytes to γδT cells and T helper 1/T helper 17 phenotypes. Stroke increased conjugated bile acids in the liver but decreased bile acids and short-chain fatty acids in the gut. Gut fermenting anaerobic bacteria decreased while opportunistic facultative anaerobes, notably Enterobacteriaceae, suffered an expansion. Anti-inflammatory treatment with a nuclear factor-κB inhibitor fully abrogated the Enterobacteriaceae overgrowth in the gut microbiota induced by stroke, whereas inhibitors of the neural or humoral arms of the stress response were ineffective at the doses used in this study. Conversely, the anti-inflammatory treatment did not prevent poststroke lung colonization by Enterobacteriaceae. CONCLUSIONS: Stroke perturbs homeostatic neuro-immuno-metabolic networks facilitating a bloom of opportunistic commensals in the gut microbiota. However, this bacterial expansion in the gut does not mediate poststroke infection.

Fermented foods: a perspective on their role in delivering biotics.

Fermented foods are often erroneously equated with probiotics. Although they might act as delivery vehicles for probiotics, or other 'biotic' substances, including prebiotics, synbiotics, and postbiotics, stringent criteria must be met for a fermented food to be considered a 'biotic'. Those criteria include documented health benefit, sufficient product characterization (for probiotics to the strain level) and testing. Similar to other functional ingredients, the health benefits must go beyond that of the product's nutritional components and food matrix. Therefore, the 'fermented food' and 'probiotic' terms may not be used interchangeably. This concept would apply to the other biotics as well. In this context, the capacity of fermented foods to deliver one, several, or all biotics defined so far will depend on the microbiological and chemical level of characterization, the reproducibility of the technological process used to produce the fermented foods, the evidence for health benefits conferred by the biotics, as well as the type and amount of testing carried out to show the probiotic, prebiotic, synbiotic, and postbiotic capacity of that fermented food.

Maternal-infant antibiotic resistance genes transference: what do we know?

Resistance to antibiotics is becoming a worldwide threat as infections caused by multidrug-resistant pathogenic microorganisms can overcome antibiotic treatments and spread quickly in the population. In the context of early life, newborns are at increased risk as their immune system is still under development, so infections and acquisition of resistance during childhood have short- and long-term consequences for the health. The moment of birth is the first exposure of infants to possible antibiotic-resistant microorganisms that may colonize their gut and other body sites. Different factors including mode of delivery, previous antibiotic exposure of the mother, gestational age and consumption of antibiotics in early-life have been described to modulate the neonate's microbiota, and thus, the resistome. Other factors, such as lactation, also impact the establishment and development of gut microbiota, but little is known about the role of breastmilk in transferring Antibiotic Resistant Genes (ARG). A deeper understanding of vertical transmission of antibiotic resistance from mothers to their offspring is necessary to determine the most effective strategies for reducing antibiotic resistance in the early life. In this review, we aim to present the current perspective on antibiotic resistances in mother-infant dyads, as well as a new insight on the study of the human gut and breastmilk resistome, and current strategies to overcome this public health problem, toward highlighting the gaps of knowledge that still need to be closed.

New gene markers for classification and quantification of Faecalibacterium spp. in the human gut.

Faecalibacterium prausnitzii is a promising biomarker of a healthy human microbiota. However, previous studies reported the heterogeneity of this species and found the presence of several distinct groups at the species level among F. prausnitzii strains. Our recent study revealed that methods previously developed for quantification of F. prausnitzii were not specific to the species level because of the heterogeneity within the F. prausnitzii species and the application of 16S rRNA gene, which is an invalid genetic marker for the species. Therefore, previously available data failed to provide information on different groups, which limits our understanding of the importance of this organism for host health. Here, we propose an alternative gene marker for quantification of F. prausnitzii-related taxa. A total of nine group-specific primer pairs were designed by targeting rpoA gene sequences. The newly developed rpoA-based qPCR successfully quantified targeted groups. Application of the developed qPCR assay in six healthy adults revealed marked differences in abundance and prevalence among the different targeted groups in stool samples. The developed assay will facilitate detailed understanding of the impact of Faecalibacterium populations at the group level on human health and to understand the links between depletion of specific groups in Faecalibacterium and different human disorders.

The Gut Microbiota in Infants: Focus on Bifidobacterium.

A long time has passed since the initial pioneering works were carried out on the composition of infant microbiota by Thedore Escherich (1857-1911) and Ernst Moro (1874-1951), and since the observations of Henry Tissier (1866-1916) which linked "Bacillus bifidus" to the health of babies [...].

Commensal Fecal Microbiota Profiles Associated with Initial Stages of Intestinal Mucosa Damage: A Pilot Study.

Progressive intestinal mucosal damage occurs over years prior to colorectal cancer (CRC) development. The endoscopic screening of polyps and histopathological examination are used clinically to determine the risk and progression of mucosal lesions. We analyzed fecal microbiota compositions using 16S rRNA gene-based metataxonomic analyses and the levels of short-chain fatty acids (SCFAs) using gas chromatography in volunteers undergoing colonoscopy and histopathological analyses to determine the microbiota shifts occurring at the early stages of intestinal mucosa alterations. The results were compared between diagnosis groups (nonpathological controls and polyps), between samples from individuals with hyperplastic polyps or conventional adenomas, and between grades of dysplasia in conventional adenomas. Some microbial taxa from the Bacillota and Euryarchaeota phyla were the most affected when comparing the diagnosis and histopathological groups. Deeper microbiota alterations were found in the conventional adenomas than in the hyperplastic polyps. The Ruminococcus torques group was enriched in both the hyperplastic polyps and conventional adenomas, whereas the family Eggerthellaceae was enriched only in the hyperplastic polyps. The abundance of Prevotellaceae, Oscillospiraceae, Methanobacteriaceae, Streptococcaceae, Christensenellaceae, Erysipelotrichaceae, and Clostridiaceae shifted in conventional adenomas depending on the grade of dysplasia, without affecting the major SCFAs. Our results suggest a reorganization of microbial consortia involved in gut fermentative processes.

Association between diet and fecal microbiota along the first year of life.

Extensive work has established the importance of the gut microbiota during the first years of life. However, there are few longitudinal studies describing the role of infants' diet on the evolution of the fecal microbiota and their metabolic activity during this stage. The aim of this work was to explore the impact of diet on the composition of the major intestinal microorganisms and their main microbial metabolites from birth to 12 months. This is a longitudinal prospective study of diet and fecal microbiota. Bacterial groups levels were determined by qPCR and short-chain fatty acids (SCFAs) concentrations by gas chromatography. Information from self-administered questionnaires about general characteristics and food frequency were obtained from a cohort of 83, Spanish and full-term, infants at 15, 90, 180 and 365 days of age. Results revealed that Enterobacteriaceae decrease in weaning period contrary to Bacteroides group and Clostridium cluster IV. CONCLUSION: our study supports weaning period as a key step for gut microbiota transition and suggests the importance of the consumption of dietary fiber with the increase of certain bacterial groups as Clostridium cluster IV, which could be beneficial for the host. Finally, studies specially designed to analyze the production and the excretion of SCFAs in children are needed to understand how diet could influence in this process.

Dietary xenobiotics, (poly)phenols and fibers: Exploring associations with gut microbiota in socially vulnerable individuals.

Objectives: Although xenobiotics derived from food processing may cause modifications in the composition of the gut microbiota (GM) evidence is scarce. The aim of this study is to evaluate the impact of potential dietary carcinogens as heterocyclic amines (HAs), polycyclic aromatic hydrocarbons (PAHs), nitrates, nitrites, nitroso compounds and acrylamide, in combination to fibers (poly)phenols on the GM composition in a group of materially deprived subjects. Study design: Transversal observational study in a sample of 19 subjects recipients of Red Cross food aid. Dietary information was recorded by means of 3 non-consecutive 24 h recalls. Questions focused on the type of cooking and the extent of cooking and roasting were included. Information on potential carcinogens was mainly obtained from the European Prospective Investigation into Cancer and Nutrition (EPIC) and Computerized Heterocyclic Amines Resource for Research in Epidemiology of Disease (CHARRED) Carcinogen Databases. Microbial composition was determined by 16S ribosomal RNA gene sequencing in fecal samples. Results: Higher levels of Lachnospiraceae and Eggerthellaceae families were found in individuals consuming less than 50 ng/day of 2-amino-3,8 dimethylimidazo (4,5,f) quinoxaline (MeIQx) (considered as lower risk dose for colorectal adenoma) while those consuming more than 40 ng/day of 2-amino-1-methyl-6-phenylimidazo (4,5,b) pyridine (PhIP) (higher risk for colorectal adenoma) showed lower relative abundance of Muribaculaceae and greater presence of Streptococcaceae and Eubacterium coprostanoligenes group. Conclusion: The associations identified between diet and processing by-products on GM in this study could be used as potential targets for the designing of dietary interventions tailored to this collective.