Stool Microbiota Research Articles

Long-term efficacy and safety of monotherapy with a single fresh fecal microbiota transplant for recurrent active ulcerative colitis: a prospective randomized pilot study

BackgroundTo assess the long-term safety and efficacy of monotherapy with a single fresh fecal microbiota transplant (FMT) for recurrent ulcerative colitis (UC).ResultsTwenty-six eligible patients were enrolled, and 6 patients were excluded. Ultimately, 20 patients were randomized to the FMT group (n = 10) and the control group (n = 10); 80% were females (F/M = 16/4), the mean age was 48 ± 14 years, and the mean duration was 6.4 ± 8.2 years. The mean length of post-FMT follow-up was 19.1 ± 10.1 months (6–38). No statistically significant differences in baseline demographic or clinical characteristics were found between the groups. Ninety percent of patients in the FMT group and 50% of patients in the control group met the primary endpoint at week 8. The Mayo score was significantly decreased compared with that of the control group (n = 10) when reassessed at week 4 (P = 0.001) and week 8 (P = 0.019) after FMT; there was no significant difference 6 months after treatment. The median remission time was 24 months (95% CI 68.26–131.7%) in both the FMT (range 6–38 months) and control groups (range 7–35 months), with no significant difference (P = 0.895). Participants tolerated FMT treatment, and no adverse events occurred during long-term follow-up, with one treatment-related significant adverse event (EBV infection) occurring within 2 weeks after FMT. Stool microbiota composition analysis indicated improved gut microbiota diversity after FMT, with expansion of stool-donor taxa. Bacteroidetes, Firmicutes and Proteobacteria were the dominant bacterial phyla of the gut microbiota in active UC patients. The relative abundance of Bacteroidetes decreased and that of Proteobacteria increased significantly in active UC patients compared with donors, while Firmicutes showed no significant changes. A single fresh FMT could effectively reconstruct the gut microbiota composition in patients with active UC and maintain stability, with increased Bacteroidetes and decreased Proteobacteria abundance. FMT significantly reduced the relative abundance of Escherichia and increased the relative abundance of Prevotella at the genus level. Pyruvate metabolism, glyoxylate and dicarboxylate metabolism, and pantothenate and CoA biosynthesis showed significant differences after transplantation.ConclusionsMonotherapy with a single fresh FMT is an effective and safe strategy to induce long-term remission without drugs in patients with active UC and may be an alternative induction therapy for recurrent UC or even primary UC.

An exercise intervention alters stool microbiota and metabolites among older, sedentary adults.

Background:Physiologic aging has been associated with gut dysbiosis. Although short exercise interventions have been linked to beneficial changes in gut microbiota in younger adults, limited data are available from older populations. We hypothesized that exercise would produce beneficial shifts in microbiota and short-chain fatty acid (SCFA) levels in older persons.Methods:Stool samples were collected before and at completion of a supervised 24-week cardiovascular and resistance exercise intervention among 50–75-year-old participants. SCFA levels were analyzed by gas chromatography and microbiome by 16S rRNA gene sequencing. Negative binomial regression models compared pre- and post-differences using false discovery rates for multiple comparison.Results:A total of 22 participants provided pre-intervention samples; 15 provided samples at study completion. At baseline, the majority of participants were men (95%), mean age 58.0 (8.8) years, mean body mass index 27.4 (6.4) kg/m2. After 24 weeks of exercise, at the genus level, exercise was associated with significant increases in Bifidobacterium (and other unidentified genera within Bifidobacteriaceae), Oscillospira, Anaerostipes, and decreased Prevotella and Oribacterium (p < 0.001). Stool butyrate increased with exercise [5.44 (95% confidence interval 1.54, 9.24) mmol/g, p = 0.02], though no significant differences in acetate or propionate (p ⩾ 0.09) were seen.Conclusion:Our pilot study suggested that an exercise intervention is associated with changes in the microbiome of older adults and a key bacterial metabolite, butyrate. Although some of these changes could potentially reverse age-related dysbiosis, future studies are required to determine the contribution of changes to the microbiome in the beneficial effect of exercise on overall health of older adults. Clinical Trials NCT02404792

Comparative Gut Microbiome Differences between Ferric Citrate and Calcium Carbonate Phosphate Binders in Patients with End-Stage Kidney Disease.

Gut dysbiosis in patients with chronic kidney disease (CKD) may induce chronic inflammation and increase morbidity. Phosphate-binding agents, generally used in patients with CKD, may potentially change the composition of the gut microbiota. This study aimed to compare the microbiota composition in hemodialysis patients treated with ferric citrate or calcium carbonate. The stool microbiota was investigated in hemodialysis patients treated with ferric citrate (n = 8) and calcium carbonate (n = 46) using 16S rRNA gene amplicon sequencing profiling using linear discriminant analysis of effect size. Further predictive functional profiling of microbial communities was obtained with Tax4Fun in R. Hemodialysis patients treated with calcium carbonate had a significantly reduced microbial species diversity (Shannon index and Simpson index) and an increased microbial alteration ratio compared with patients treated with ferric citrate. A distinct microbial community structure was found in patients treated with ferric citrate, with an increased abundance of the Bacteroidetes phylum and a decreased abundance of the phylum Firmicutes. Members of the order Lactobacillales were enriched in patients treated with calcium carbonate, whereas taxa of the genera Ruminococcaceae UCG-004, Flavonifractor, and Cronobacter were enriched in patients treated with ferric citrate phosphate binder. In conclusion, Ferric citrate therapy results in a more diverse microbiome community compared to calcium carbonate therapy in hemodialysis patients with phosphate binder treatment. The gut microbiome reflects the phosphate binder choice in hemodialysis patients, further affecting the physiological environment in the gastrointestinal tract.

Stool microbiome, pH and short/branched chain fatty acids in infants receiving extensively hydrolyzed formula, amino acid formula, or human milk through two months of age

BackgroundEarly infant feeding with intact or extensively hydrolyzed (EH) proteins or free amino acids (AA) may differentially affect intestinal microbiota composition and immune reactivity. This multicenter, double-blind, controlled, parallel-group, pilot study compared stool microbiota from Baseline (1–7 days of age) up to 60 days of age in healthy term infants who received mother’s own milk (assigned to human milk [HM] reference group) (n = 25) or were randomized to receive one of two infant formulas: AA-based (AAF; n = 25) or EH cow’s milk protein (EHF; n = 28). Stool samples were collected (Baseline, Day 30, Day 60) and 16S rRNA genes were sequenced. Alpha (Shannon, Simpson, Chao1) and beta diversity (Bray Curtis) were analyzed. Relative taxonomic enrichment and fold changes were analyzed (Wilcoxon, DESEq2). Short/branched chain fatty acids (S/BCFA) were quantified by gas chromatography. Mean S/BCFA and pH were analyzed (repeated measures ANOVA).ResultsAt baseline, alpha diversity measures were similar among all groups; however, both study formula groups were significantly higher versus the HM group by Day 60. Significant group differences in beta diversity at Day 60 were also detected, and study formula groups were compositionally more similar compared to HM. The relative abundance of Bifidobacterium increased over time and was significantly enriched at Day 60 in the HM group. In contrast, a significant increase in members of Firmicutes for study formula groups were detected at Day 60 along with butyrate-producing species in the EHF group. Stool pH was significantly higher in the AAF group at Days 30 and 60. Butyrate increased significantly from Baseline to Day 60 in the EHF group and was significantly higher in study formula groups vs HM at Day 60. Propionate was also significantly higher for EHF and AAF at Day 30 and AAF at Day 60 vs HM. Total and individual BCFA were higher for AAF and EHF groups vs HM through Day 60.ConclusionsDistinct patterns of early neonatal microbiome, pH, and microbial metabolites were demonstrated for infants receiving mother’s own milk compared to AA-based or extensively hydrolyzed protein formula. Providing different sources of dietary protein early in life may influence gut microbiota and metabolites.Trial registrationClinicalTrials.gov Identifier: NCT02500563. Registered July 28, 2015.

Defining Microbiome Readiness for Surgery: Dietary Prehabilitation and Stool Biomarkers as Predictive Tools to Improve Outcome.

Determine whether preoperative dietary prehabilitation with a low-fat, high-fiber diet reverses the impact of Western diet (WD) on the intestinal microbiota and improves postoperative survival. We have previously demonstrated that WD fed mice subjected to an otherwise recoverable surgical injury (30% hepatectomy), antibiotics, and a short period of starvation demonstrate reduced survival (29%) compared to mice fed a low-fat, high-fiber standard chow (SD) (100%). Mice were subjected to 6 weeks of a WD and underwent dietary pre-habilitation (3 days vs 7 days) with a SD prior to exposure to antibiotics, starvation, and surgery. 16S rRNA gene sequencing was utilized to determine microbiota composition. Mass spectrometry measured short chain fatty acids and functional prediction from 16S gene amplicons were utilized to determine microbiota function. As early as 24 hours, dietary prehabilitation of WD mice resulted in restoration of bacterial composition of the stool microbiota, transitioning from Firmicutes dominant to Bacteroidetes dominant. However, during this early pre-habilitation (ie, 3 days), stool butyrate per microbial biomass remained low and postoperative mortality remained unchanged from WD. Microbiota function demonstrated reduced butyrate contributing taxa as potentially responsible for failed recovery. In contrast, after 7 days of prehabilitation (7DP), there was greater restoration of butyrate producing taxa and survival after surgery improved (29% vs 79% vs 100%: WD vs 7DP vs SD, P < 0.001). The deleterious effects of WD on the gut microbiota can be restored after 7 days of dietary prehabilitation. Moreover, stool markers may define the readiness of the microbiome to withstand the process of surgery including exposure to antibiotics and short periods of starvation.

Assessing the efficacy and impact of a personalised smoking cessation intervention among type 2 diabetic smokers: study protocol for an open-label randomised controlled trial (DISCGO-RCT)

IntroductionFew studies have assessed the efficacy of smoking cessation interventions in individuals with type 2 diabetes, but interventions adapted to the specific needs of this population are warranted. The aim...

The reproducibility and stability of stool microbiota during collection and transport of stool specimen

Background/Aim: The role of gut microbiome in epidemiologic research is increasingly recognized and with it the number of studies analyzing stool specimen is rapidly expanding. However, currently there are no standardized protocols for collecting, transporting and storing stool specimen in population-based environmental research covering a large geographic area. For home data collection, it takes between 12-100 hours from stool collection to time of sample processing in the lab. The aim of the study is to test the stability and reproducibility of stool microbiota during the transit period and provide guidance on collecting stool in population-based studies. Methods: Fresh stool was collected from 12 volunteers. Samples were aliquoted into cryovials within 30 min of collection. Three aliquots from each sample were frozen immediately (time 0) and remaining aliquots were kept at 4oC for 6, 24, 48, 72 and 96 hours followed by storage at -80oC. Three aliquots per sample were analyzed for each time point to assess reproducibility. The composition of stool microbiota was assessed by DNA sequencing of 16s rRNA V4 region. Results: The intraclass correlation coefficient (ICC) for repeated measures was between 0.6-1.0 for α-diversity measures ACE, Chao1, Shannon, and Inverse Simpson. The ICC for relative abundance of four major phyla (Bacteroidetes, Firmicutes, Proteobacteria and Actinobacteria) between time 0 and 6 hours at 4oC was 0.9-1.0. The correlation remained excellent (0.9-1.0) for Proteobacteria and Actinobacteria, but was moderate (ICC from 0.6 to 0.7) for Bacteroidetes and Firmicutes between 24-96 hours at 4oC. Conclusions: Results suggest that a) the moderate correlation of repeated assessments from some of the samples suggests that stool specimen should be homogenized before taking aliquots, and b) stool microbiota is relatively stable at 4oC for up to 96 hours. However, some bacterial taxa had altered relative abundance suggesting they are more sensitive to storage conditions.

Effect of Bifidobacterium infantis NLS super strain in symptomatic coeliac disease patients on long-term gluten-free diet - an exploratory study.

Bifidobacterium infantis NLS super strain (B. infantis NLS-SS) was previously shown to alleviate gastrointestinal symptoms in newly diagnosed coeliac disease (CD) patients consuming gluten. A high proportion of patients following a gluten-free diet experiences symptoms despite dietary compliance. The role of B. infantis in persistently symptomatic CD patients has not been explored. The aim of the study was to evaluate the effect of B. infantis NLS-SS on persistent gastrointestinal symptoms in patients with CD following a long-term GFD. We conducted a randomised, cross-over, double-blind, placebo-controlled trial in symptomatic adult CD patients on a GFD for at least two years. After one-week run-in, patients were randomised to B. infantis NLS-SS or placebo for 3 weeks with cross-over after a 2-week wash-out period. We estimated changes (Δ) in celiac symptom index (CSI) before and after treatment. Stool samples were collected for faecal microbiota analysis (16S rRNA sequencing). Gluten immunogenic peptide (GIP) excretion in stool and urine samples was measured at each study period. Eighteen patients were enrolled; six patients were excluded due violations in protocol. For patients with the highest clinical burden, CD symptoms were lower in probiotic than in placebo treatment (P=0.046). B. infantis and placebo treated groups had different microbiota profiles as assessed by beta diversity clustering. In probiotic treated groups, we observed an increase in abundance of B. infantis. Treatment with B. infantis was associated with decreased abundance of Ruminococcus sp. and Bifidobacterium adolescentis. GIP excretion in stools and urine was similar at each treatment period. There were no differences in adverse effects between the two groups. B. infantis NLS-SS improves specific CD symptoms in a subset of highly symptomatic treated patients (GFD). This is associated with a shift in stool microbiota profile. Larger studies are needed to confirm these findings. ClinicalTrials.gov: NCT03271138.

S1014 The Modest Differential Effects of Rifaximin Alone vs Rifaximin Plus Lactulose on Intestinal Microbial Diversity and Composition in Patients With Cirrhosis

INTRODUCTION: Rifaximin, a nonsystemic antibiotic, is indicated in the United States for reducing the risk of overt hepatic encephalopathy (OHE) recurrence in adults and may be used alone or in combination with lactulose. This analysis employed genomic characterization to assess the impact of daily rifaximin alone or rifaximin + lactulose treatment on stool microbiota in patients with a history of OHE. METHODS: In a randomized, open-label trial, patients aged ≥18 y with cirrhosis and history of ≥1 OHE episode during the prior 6 months, currently in HE remission (Conn score ≤1), received rifaximin 550 mg twice daily (BID) or rifaximin 550 mg BID + lactulose (titrated to 2–3 soft stools/d) for 6 months. Stool samples were collected at screening (baseline) and month 6/end of treatment (EOT). Patients were randomly selected for the stool microbiota sequencing analysis substudy. Genomic characterization of microbiota was achieved using 16S rRNA bacterial deep gene sequencing. Metrics included stool microbiota richness (number of bacterial species in a sample, adjusted for different numbers of sequences observed from each sample), evenness (relative abundance of different species [range, 0–1; 1 = complete evenness]), and Shannon diversity index (richness and evenness [overall community complexity]). RESULTS: Sixty-six adults (mean age, 56.0 y; 68.2% male; mean body mass index, 31.7 kg/m2) were randomly selected for stool microbiota analysis (rifaximin alone [n = 34]; rifaximin + lactulose [n = 32]; demographics evenly matched). At baseline, measures of richness and evenness of stool microbiota and Shannon diversity index were similar for rifaximin alone and rifaximin + lactulose groups (Table 1). Stool microbiota richness did not significantly change from baseline to EOT in either group; no significant difference was observed between groups. Significant decreases from baseline to EOT were seen in evenness of stool microbiota and Shannon diversity index in the rifaximin alone group (P < 0.005 for both measures); greater reductions in these parameters were observed in the rifaximin alone group versus the rifaximin + lactulose group (P < 0.05 for both measures). CONCLUSION: Modest effects on stool microbiota diversity and evenness, with no effects on the absolute number of species, were observed in the rifaximin alone group. Concomitant lactulose may offset these effects, but further research is needed. Overall, data support that overall effects to stool microbiota during rifaximin treatment are modest in scope.Table 1

Role of a Ketogenic Diet on Body Composition, Physical Health, Psychosocial Well-Being and Sports Performance in Athletes: A Scoping Review.

Background: Recently, a focus has been placed on investigating the potential benefits of adherence to a ketogenic diet in enhancing body composition, physical health, psychological well-being, and performance of athletes from various sporting disciplines. As the available research is yet to be collated and analyzed in a single review, this scoping review aims to analyze and draw conclusions from the available literature that exists on the efficacy of a ketogenic diet among athletic populations. Methods: Several primary research databases and any relevant citation lists were searched to locate appropriate studies for inclusion in this scoping review. Studies that investigated the effects of adherence to a ketogenic diet (KD), defined by a carbohydrate intake of less than 5% of total energy intake, on body composition, physical health, psychological well-being, and performance among an athletic population were included in the review. From 814 articles screened, 12 were identified as meeting the inclusion criteria and were included in the final scoping review. Results: Adherence to a KD has beneficial effects on body weight and fat mass. Varying effects were identified on physical health with the diet, eliciting positive effects on fat oxidation but potentially deleterious effects on stool microbiota and iron metabolism. Conflicting results were reported regarding the effects of a KD on sporting performance. Benefits were reported regarding athlete well-being following commencement of a KD, but only after week two. Conclusions: The results of this scoping review demonstrate that there are both beneficial and detrimental effects associated with adherence to a KD among athletic populations. It is understood that further research is required to make any concrete recommendations regarding a KD to athletes.

In search for interplay between stool microRNAs, microbiota and short chain fatty acids in Crohn\u2019s disease - a preliminary study

BackgroundInflammatory bowel diseases are classic polygenic disorders, with genetic loads that reflect immunopathological processes in response to the intestinal microbiota. Herein we performed the multiomics analysis by combining the large scale surveys of gut bacterial community, stool microRNA (miRNA) and short chain fatty acid (SCFA) signatures to correlate their association with the activity of Crohn’s disease (CD).MethodsDNA, miRNA, and metabolites were extracted from stool samples of 15 CD patients, eight with active disease and seven in remission, and nine healthy individuals. Microbial, miRNA and SCFA profiles were assessed using datasets from 16S rRNA sequencing, Nanostring miRNA and GC-MS targeted analysis, respectively.ResultsPairwise comparisons showed that 9 and 23 taxa differed between controls and CD patients with active and inactive disease, respectively. Six taxa were common to both comparisons, whereas four taxa differed in CD patients. α-Diversity was lower in both CD groups than in controls. The levels of 13 miRNAs differed (p-value < 0.05; FC > 1.5) in CD patients and controls before FDR correction and 4 after. Of six SCFAs, the levels of two differed significantly (p-value < 0.05, FC > 1.5) in CD patients and controls, and the levels of four differed in patients with active and inactive CD. PLS-DA revealed models with smallest error rate for controls in bacterial component and inactive disease in metabolites.ConclusionA complex interrelationship may exist between gut dysbiosis, miRNA profiling and SCFA level in response to intestinal inflammation.

Bifidobacterium breve BBG-001 and intestinal barrier function in preterm babies: Exploratory Studies from the PiPS Trial.

Uncertainty remains about the role of probiotics to prevent necrotising enterocolitis (NEC) some of which arises from the variety of probiotic interventions used in different trials, many with no prior evidence of potential efficacy. Mechanistic studies of intestinal barrier function embedded in a large probiotic trial could provide evidence about which properties of probiotics might be important for NEC prevention thus facilitating identification of strains with therapeutic potential. Intestinal permeability, stool microbiota, SCFAs and mucosal inflammation were assessed from the second postnatal week in babies enrolled to a randomised controlled trial of B. breve BBG-001 (the PiPS trial). Results were compared by allocation and by stool colonisation with the probiotic. Ninety-four preterm babies were recruited across six nested studies. B. breve BBG-001 content was higher by allocation and colonisation; Enterobacteriaceae and acetic acid levels were higher by colonisation. No measure of intestinal barrier function showed differences. The PiPS trial found no evidence of efficacy to reduce NEC. That the negative results of the PiPS trial were associated with failure of this probiotic to modify intestinal barrier function supports the possibility that the tests described here have the potential to identify strains to progress to large clinical trials. Uncertainty about the therapeutic role of probiotics to prevent necrotising enterocolitis is in part due to the wide range of bacterial strains with no previous evidence of efficacy used in clinical trials. We hypothesised that mechanistic studies embedded in a probiotic trial would provide evidence about which properties of probiotics might be important for NEC prevention. The finding that the probiotic strain tested, Bifidobacterium breve BBG-001, showed neither effects on intestinal barrier function nor clinical efficacy supports the possibility that these tests have the potential to identify strains to progress to large clinical trials.

Effect of donor human milk on host-gut microbiota and metabolic interactions in preterm infants

Human milk is the gold standard for infant nutrition. Preterm infants whose mothers are unable to provide sufficient own mother's milk (OMM), receive pasteurized donor human milk (DHM). We studied metabolic signatures of OMM and DHM and their effect on the interplay of the developing microbiota and infant's metabolism. Metabolic fingerprinting of OMM and DHM as well as infant's urine was performed using liquid chromatography-mass spectrometry and the infant's stool microbiota was analyzed by 16S rRNA sequencing. Significant differences in the galactose and starch and sucrose metabolism pathways when comparing OMM and DHM, and alterations of the steroid hormone synthesis and pyrimidine metabolism pathways in urine were observed depending on the type of feeding. Differences in the gut-microbiota composition were also identified. The composition of DHM differs from OMM and feeding of DHM has a significant impact on the metabolic phenotype and microbiota of preterm infants. Our data help to understand the origin of the observed changes generating new hypothesis: i) steroid hormones present in HM have a significant influence in the activity of the steroid hormone biosynthesis pathway in preterm infants; ii) the pyrimidine metabolism is modulated in preterm infants by the activity of gut-microbiota. Short- and long-term implications of the observed changes for preterm infants need to be assessed in further studies.

Gut microbiota signatures and clinical manifestations in celiac disease children at onset: a pilot study.

Recent researches have shown an altered gut microbiota in celiac disease (CD) patients compared with healthy controls (HCs). This study aims to evaluate the composition of the microbiota of CD children at onset and the relationship between bacterial abundances and symptoms. Celiac disease patients were consecutively enrolled at a pediatric unit referring for suspected CD. HCs were also included in the study. Stool and duodenal samples were collected and evaluated by a high taxonomic fingerprint microbiota array. Thirty-seven subjects enrolled: 21 CD patients and 16 HCs. Fourteen subjects were male (38%). The mean age was 75months (standard deviation 31.5) for CD patients and 71months (standard deviation 34.9) for HCs. Duodenal microbiota of CD patients showed a dominance of Enterobacteriaceae and subdominance of Bacteroidetes/Streptococcus. Stool microbiota showed a lower abundance of Bacteroides-Prevotella (P=0.013), Akkermansia (P=0.002), and Staphylococcaceae (P=0.001) in CD patients compared with HC. At symptoms level, an increased mean relative abundance of Bacillaceae and Enterobaeriaceae in patients with abdominal pain (P=0.007 and P=0.010) was found. CD patients with diarrhea had reduced mean relative abundance of Clostridium cluster XIVa (P=0.044) and Akkermansia (P=0.033) and an increase in Bacillaceae (P=0.048) and Fusobacterium (P=0.048). Gut microbiota of CD children at disease onset is different from that of HC. Pro-inflammatory microbiota imbalances were associated with CD symptoms. Further studies are needed to assess whether dysbiosis is associated with CD early onset and symptoms.

Challenges in diagnosing necrotizing enterocolitis.

One of the many challenges with necrotizing enterocolitis (NEC) remains our inability to make an accurate diagnosis of NEC. The lack of a unifying cause and multiple variations in presentations lead to great uncertainty with NEC. Separating out the needs of the researcher wanting to define NEC from the clinician and patient family's perspectives who want an accurate diagnosis for NEC is important. The need to augment and/or replace the outdated modified Bell staging criteria is crucial to improving NEC management. Emerging literature suggests that genetic susceptibility and stool microbiota signatures may help identify preterm infants at increased risk of the disease. Ongoing studies using single or multi-omic approaches may help to characterize biomarkers that will aid in the prediction or early diagnosis of NEC, as well as differentiate other causes of severe bowel injury. Bowel ultrasound shows promise in improving our diagnostic accuracy for NEC but has been slow in adoption. Patient family perspectives are key in accelerating our efforts to integrate newer diagnostic methods into practice.

Salivary and stool microbiota differences are related to differences in 90-day hospitalizations in Mexican compared to American patients with cirrhosis

Salivary and stool microbiota differences are related to differences in 90-day hospitalizations in Mexican compared to American patients with cirrhosis

Microbiota assembly, structure, and dynamics among Tsimane horticulturalists of the Bolivian Amazon

Selective and neutral forces shape human microbiota assembly in early life. The Tsimane are an indigenous Bolivian population with infant care-associated behaviors predicted to increase mother-infant microbial dispersal. Here, we characterize microbial community assembly in 47 infant-mother pairs from six Tsimane villages, using 16S rRNA gene amplicon sequencing of longitudinal stool and tongue swab samples. We find that infant consumption of dairy products, vegetables, and chicha (a fermented drink inoculated with oral microbes) is associated with stool microbiota composition. In stool and tongue samples, microbes shared between mothers and infants are more abundant than non-shared microbes. Using a neutral model of community assembly, we find that neutral processes alone explain the prevalence of 79% of infant-colonizing microbes, but explain microbial prevalence less well in adults from river villages with more regular access to markets. Our results underscore the importance of neutral forces during microbiota assembly. Changing lifestyle factors may alter traditional modes of microbiota assembly by decreasing the role of neutral processes.

P0272COMPARATIVE GUT MICROBIOME DIFFERENCES BETWEEN FERRIC CITRATE AND CALCIUM CARBONATE PHOSPHATE BINDER TREATMENT IN HEMODIALYSIS PATIENTS

Abstract Background and Aims Gut microbiome alteration increases uremic toxin levels inducing chronic inflammation and leading morbidity and mortality in patients with chronic kidney disease. Phosphate-binding agents may potentially change the composition of the gut microbiota. However, the limited clinical study investigates the microbiome difference between iron-containing and calcium-containing phosphate binders. The aim of this study was to compare the microbiota composition in hemodialysis patients treated with ferric citrate or calcium carbonate. Method The stool microbiota was investigated in hemodialysis patients with ferric citrate used (n=8) and calcium carbonate used (n=46) by 16S rRNA next-generation gene sequencing profiling. The altered microbiota between two different phosphate binders was analyzed. Differences in the microbial composition of the two patient groups were assessed using linear discriminant analysis effect size. Results Hemodialysis patients with calcium carbonate used revealed significantly reduced microbial species diversity (Shannon index and Simpson index) and increased microbial dysbiosis index compared with ferric citrate users. Compared to patients taking calcium carbonate, a distinct microbial community structure in patients taking ferric citrate, with an increased abundance of Bacteroidetes phylum and decreased abundance of phylum Firmicutes. In comparison between two phosphate binder users, members of the order Lactobacillales were prominent in calcium carbonate therapy, including family Streptococcaceae and genus Streptococcus. In contrast, taxa of the genus Ruminococcaceae, Flavonifractor, and Cronobacter were enriched in ferric citrate phosphate binder users. Conclusion The fecal microbiota was richer and more diverse in the ferric citrate group than in the calcium carbonate group. Hemodialysis patients with ferric citrate used were associated with differences in the gut microbiome composition compared to calcium carbonate users.

Human milk microbiota associated with early colonization of the neonatal gut in Mexican newborns.

BackgroundHuman milk microbiota plays a role in the bacterial colonization of the neonatal gut, which has important consequences in the health and development of the newborn. However, there are few studies about the vertical transfer of bacteria from mother to infant in Latin American populations.MethodsWe performed a cross-sectional study characterizing the bacterial diversity of 67 human milk-neonatal stool pairs by high-throughput sequencing of V3-16S rDNA libraries, to assess the effect of the human milk microbiota on the bacterial composition of the neonate’s gut at early days.ResultsHuman milk showed higher microbial diversity as compared to the neonatal stool. Members of the Staphylococcaceae and Sphingomonadaceae families were more prevalent in human milk, whereas the Pseudomonadaceae family, Clostridium and Bifidobacterium genera were in the neonatal stool. The delivery mode showed association with the neonatal gut microbiota diversity, but not with the human milk microbiota diversity; for instance, neonates born by C-section showed greater richness and diversity in stool microbiota than those born vaginally. We found 25 bacterial taxa shared by both ecosystems and 67.7% of bacteria found in neonate stool were predicted to originate from human milk. This study contributes to the knowledge of human milk and neonatal stool microbiota in healthy Mexican population and supports the idea of vertical mother-neonate transmission through exclusive breastfeeding.

Phase II study of durvalumab plus total neoadjuvant therapy (TNT) in locally advanced rectal cancer: The GEMCAD-1703 DUREC trial.

TPS4122 Background: In clinical stages II and III (cT3-4 and/or N+), preoperative chemoradiotherapy (CRT) or short-course radiation followed by total mesorectal escision (TME) have been the standard of care for the last 15 years. Induction chemotherapy (CT) before CRT (strategy known as TNT) results in fewer toxic effects and improved compliance. TNT may release tumor-neoantigens with platinum-based induction CT, and radiotherapy has the potential ability to induce an immunogenic cell death and counteract an immune-suppressive tumor microenvironment that provides the rationale for combining with immunotherapies. In addition, the presence of tumor infiltrating lymphocytes has been demonstrated in patients with rectal cancer treated with neoadjuvant CRT, reinforcing the rational for immune check-point inhibitors in this setting. We hypothesize that combining TNT with durvalumab (an optimized monoclonal antibody directed against programmed cell death-1 ligand 1) would improve outcome. Methods: DUREC is a multicenter, single-arm, open-label, phase Ib/II study for patients with magnetic resonance (mr) image middle or distal third, mrT3c-d/T4/N2 rectal adenocarcinoma. Treatment: Patients will receive 6 cycles of modified FOLFOX6 prior to CRT (capecitabine with 50.4 Gy in 28 fractions) and TME, combined with durvalumab 1500 mg every 4 weeks during induction CT, CRT and waiting period until surgery. To assess the tolerability and toxicity profile we plan to perform a run-in treatment phase including the first 6 patients in the study, holding recruitment until all of them will be operated and 30-days post-surgery period completed. If ≤ 2 durvalumab-related dose-limiting toxicities (DLTs) are observed, recruitment will continue. The primary objective is pathological complete response (pCR) rate. Secondary endpoints include toxicity, tumor regression grade, R0 resections, clear circumferential margins, surgical complications, NAR score, disease-free survival and a biomarker program on tumor tissue, blood samples and stool microbiota. Statistical design: 58 evaluable patients (assuming a P0 of 16% and a P1 of 30%, with 0.1 alpha and 0.1 beta); Study started recruitment on December 2019. Clinical trial information: 2018-004835-56 .