Microbiota Of Healthy Subjects Research Articles

The Interaction between the Oral Microbiome and Systemic Diseases: A Narrative Review

Background: The human being is defined as a ‘superorganism’ since it is made up of its own cells and microorganisms that reside inside and outside the human body. Commensal microorganisms, which are even ten times more numerous than the cells present in the body, perform very important functions for the host, as they contribute to the health of the host, resist pathogens, maintain homeostasis, and modulate the immune system. In the mouth, there are different types of microorganisms, such as viruses, mycoplasmas, bacteria, archaea, fungi, and protozoa, often organized in communities. The aim of this umbrella review is to evaluate if there is a connection between the oral microbiome and systematic diseases. Methodology: A literature search was conducted through PubMed/MEDLINE, the COCHRANE library, Scopus, and Web of Science databases without any restrictions. Because of the large number of articles included and the wide range of methods and results among the studies found, it was not possible to report the results in the form of a systematic review or meta-analysis. Therefore, a narrative review was conducted. We obtained 73.931 results, of which 3593 passed the English language filter. After the screening of the titles and abstracts, non-topic entries were excluded, but most articles obtained concerned interactions between the oral microbiome and systemic diseases. Discussion: A description of the normal microbial flora was present in the oral cavity both in physiological conditions and in local pathological conditions and in the most widespread systemic pathologies. Furthermore, the therapeutic precautions that the clinician can follow in order to intervene on the change in the microbiome have been described. Conclusions: This review highlights what are the intercorrelations of the oral microbiota in healthy subjects and in subjects in pathological conditions. According to several recent studies, there is a clear correlation between dysbiosis of the oral microbiota and diseases such as diabetes, cardiovascular diseases, chronic inflammatory diseases, and neurodegenerative diseases.

Longitudinal Characterization of the Fungal Skin Microbiota in Healthy Subjects Over a Period of 1 Year

Beneficial microorganisms on the skin contribute to the first line of defense against attacking pathogens. However, instability of the skin microbiota is associated with skin diseases. Hence, temporal analyses are crucial because they serve as a baseline to understand the development of dysbiosis in disease. In this study, we aim to improve the understanding of the fungal skin microbiota, the mycobiota, in healthy subjects. Skin swabs were taken monthly for a year from four different skin sites, that is, antecubital crease, dorsal neck, glabella, and vertex, and analyzed by DNA sequencing of the internal transcribed spacer 1 region. The mycobiota on the skin was dominated by the class Malasseziomycetes, and the core community was composed of Malassezia restricta, M. globosa, and M.sympodialis at all skin sites. Over the period of 1 year, the intrapersonal mycobiota remained largely stable, with some fluctuations of low abundant non-Malassezia fungi. We conclude that despite fluctuations of low abundant classes, fungal skin communities form a temporally robust and individual fingerprint in healthy subjects.

Evaluation of changes in intestinal microbiota in Crohn\u2019s disease patients after anti-TNF alpha treatment

Intestinal dysbiosis is key in the onset and development of Crohn’s disease (CD). We evaluated the microbiota changes in CD patients before and after a six-month anti-TNF treatment, comparing these changes with the microbiota of healthy subjects. This prospective multicenter observational study involved 27 CD patients initiating anti-TNF treatment and 16 healthy individuals. Inflammatory activity was determined at baseline, 3 and 6 months, classifying patients into responders and non-responders. Fecal microbiota was analyzed by massive genomic sequencing thought 16S rRNA amplicon sequencing before and after six months of anti-TNF treatment. The CD cohort showed a decrease in genera of the class Clostridia, short-chain fatty acid producers, and an increase in the phylum Proteobacteria (p < 0.01) versus the healthy cohort. After anti-TNF treatment, the phylum Proteobacteria also increased in non-responders versus responders (13/27) (p < 0.005), with the class Clostridia increasing. In addition, alpha diversity increased in responders versus non-responders (p < 0.01), tending towards eubiosis. An association was found (p < 0.001) in the F.prausnitzii/E.coli ratio between responders and non-responders. The F/E ratio was the most accurate biomarker of anti-TNF response (area under the curve 0.87). Thus, anti-TNF treatment allows partial restoration of intestinal microbiota in responders and the F.prausnitzii/E.coli ratio can provide a reliable indicator of response to anti-TNF in CD.

Probiotics Do Not Alter the Long-Term Stability of the Supragingival Microbiota in Healthy Subjects: A Randomized Controlled Trial.

Background: The purpose of the present study was to longitudinally characterize the supragingival microbiota throughout a three months period in orally healthy individuals. We tested the hypothesis that the supragingival microbiota shows a high degree of compositional stability, which is resilient against the external perturbation of regular use of probiotics, as long as oral health is maintained. Methods: The present study was a double-blinded, randomized, placebo-controlled clinical trial. The study population comprised a total of 110 oral and systemic healthy individuals, distributed in a probiotic (n = 55) and placebo (n = 55) group, where the test group consumed tablets with the probiotic strains Lacticaseibacillus rhamnosus (formerly Lactobacillus) PB01 DSM14870 and Latilactobacillus curvatus (formerly Lactobacillus) EB10 DSM32307 for a period of 12 weeks. Supragingival plaque samples and clinical registrations were performed at baseline, and after 4, 8, and 12 weeks, respectively. The supragingival microbiota was characterized by means of 16S rDNA sequencing. Sequences were referenced against the HOMD database. Results: No significant changes of the core microbiota, as expressed by relative abundance of predominant genera and species were evident during the three months observation period in the probiotic or the placebo group. Conclusions: Data from the present study clearly demonstrate long term compositional stability of the supragingival microbiota as long as oral health is maintained. In addition, the tested probiotics had no augmenting effect on the supragingival microbiota in oral health.

Microbiota, renal disease and renal transplantation.

Aim of this frontier review has been to highlight the role of microbiota in healthy subjects and in patients affected by renal diseases with particular reference to renal transplantation. The microbiota has a relevant role in conditioning the healthy status and the diseases. In particular gut microbiota is essential in the metabolism of food and has a relevant role for its relationship with the immune system. The indigenous microbiota in patients with chronic renal failure is completely different than that of the healthy subjects and pathobionts appear. This abnormality in microbiota composition is called dysbiosis and may cause a rapid deterioration of the renal function both for activating the immune system and producing large quantity of uremic toxins. Similarly, after renal trans-plantation the microbiota changes with the appearance of pathobionts, principally in the first period because of the assumption of immunosuppressive drugs and antibiotics. These changes may deeply interfere with the graft outcome causing acute rejection, renal infections, diarrhea, and renal interstitial fibrosis. In addition, change in the microbiota may modify the metabolism of immuno-suppressive drugs causing in some patients the need of modifying the immunosuppressant dosing. The restoration of the indigenous microbiota after transplantation is important, either to avoiding the complications that impair the normal renal graft, and because recent studies have documented the role of an indigenous microbiota in inducing tolerance towards the graft. The use of prebiotics, probiotics, smart bacteria and diet modification may restore the indigenous microbiota, but these studies are just at their beginning and more data are needed to draw definitive conclusions.

Tetracycline and multidrug resistance in the oral microbiota: differences between healthy subjects and patients with periodontitis in Spain

ABSTRACT Introduction: Antibiotic resistance is widely found even among bacterial populations not having been exposed to selective pressure by antibiotics, such as tetracycline. In this study we analyzed the tetracycline-resistant subgingival microbiota of healthy subjects and of patients with periodontitis, comparing the prevalence of tet genes and their multidrug resistance profiles. Methods: Samples from 259 volunteers were analyzed, obtaining 813 tetracycline-resistant isolates. The prevalence of 12 antibiotic resistance genes was assessed, and multidrug profiles were built. Each isolate was identified by 16S rRNA sequencing. Differences in qualitative data and quantitative data were evaluated using the chi-square test and the Mann-Whitney-U test, respectively. Results: tet(M) was the most frequently detected tet gene (52.03%). We observed significant differences between the prevalence of tet(M), tet(W), tet(O), tet(32) and tet(L) in both populations studied. Multidrug resistance was largely observed, with resistance to kanamycin being the most detected (83.64%). There were significant differences between the populations in the prevalence of kanamycin, chloramphenicol, and cefotaxime resistance. Resistant isolates showed significantly different prevalence between the two studied groups. Conclusion: The high prevalence of multidrug resistance and tetracycline resistance genes found in the subgingival microbiota, highlights the importance of performing wider and more in-depth analysis of antibiotic resistance in the oral microbiota.

The gut microbiome in Parkinson's disease: A culprit or a bystander?

In recent years, large-scale metagenomics projects such as the Human Microbiome Project placed the gut microbiota under the spotlight of research on its role in health and in the pathogenesis several diseases, as it can be a target for novel therapeutical approaches. The emerging concept of a microbiota modulation of the gut-brain axis in the pathogenesis of neurodegenerative disorders has been explored in several studies in animal models, as well as in human subjects. Particularly, research on changes in the composition of gut microbiota as a potential trigger for alpha-synuclein (α-syn) pathology in Parkinson's disease (PD) has gained increasing interest. In the present review, we first provide the basis to the understanding of the role of gut microbiota in healthy subjects and the molecular basis of the gut-brain interaction, focusing on metabolic and neuroinflammatory factors that could trigger the alpha-synuclein conformational changes and aggregation. Then, we critically explored preclinical and clinical studies reporting on the changes in gut microbiota in PD, as compared to healthy subjects. Furthermore, we examined the relationship between the gut microbiota and PD clinical features, discussing data consistently reported across studies, as well as the potential sources of inconsistencies. As a further step toward understanding the effects of gut microbiota on PD, we discussed the relationship between dysbiosis and response to dopamine replacement therapy, focusing on Levodopa metabolism. We conclude that further studies are needed to determine whether the gut microbiota changes observed so far in PD patients is the cause or, instead, it is merely a consequence of lifestyle changes associated with the disease. Regardless, studies so far strongly suggest that changes in microbiota appears to be impactful in pathogenesis of neuroinflammation. Thus, dysbiotic microbiota in PD could influence the disease course and response to medication, especially Levodopa. Future research will assess the impact of microbiota-directed therapeutic intervention in PD patients.

Spatial Analysis of the Intestinal Microbiota in Healthy Subjects

Spatial Analysis of the Intestinal Microbiota in Healthy Subjects

Intestinal microbiota assessment in cirrhotic patients from a Mexican mestizo population.

The intestinal microbiota is significantly altered in cirrhotic patients, but the composition of the intestinal microbiota in Mexican patients with the pathology has not been reported. The present study is an attempt to determine the type of intestinal microbiota in healthy subjects and in patients of Mexican mestizo origin that present with cirrhosis of the liver. Biochemical liver function parameters (ALT, AST, GGT, BIL-T, etc.) were determined in 23 cirrhotic patients and 21 control subjects. The intestinal microbiota was established through 16S ribosomal RNA gene sequencing. The cirrhotic patients had elevated levels of ALT, AST, GGT (105.2±77.7 vs. 20.99±8.5UI/L, 110±68.6 vs. 23.39±5.2, and 119.1±79.1 vs. 19.3±15.2UI/L, respectively), IL-6 (1.64±0.38pg/ml, P<.001), or TNFα (1.78±0.3, P<.05). The intestinal microbiota of the cirrhotic patients was less diverse, compared with that of the control subjects. At the level of the phylum, there was a significant increase in Proteobacteria and Bacteroidetes in the patients with cirrhosis, compared with the controls (6.2 vs. 4.9% and 44 vs. 46%, respectively, P<.01). In contrast, there was a decrease in Firmicutes, Actinobacteria, and Fusobacteria in the cirrhotic patients. There was an increase in the Campylobacter and Gemella families in the cirrhotic patients, whereas Streptococcus and Veillonella had a positive association with serum ALT or AST levels. To the best of our knowledge, the present study is the first to demonstrate the type of intestinal microbiota in Mexican patients with cirrhosis of the liver. The extension of the findings in a larger cohort of subjects and the metagenome analysis will enable the creation of data that can have relevant treatment implications for this group of patients in Mexico.

Intestinal microbiota assessment in cirrhotic patients from a Mexican mestizo population

Introduction and aimsThe intestinal microbiota is significantly altered in cirrhotic patients, but the composition of the intestinal microbiota in Mexican patients with the pathology has not been reported. The present study is an attempt to determine the type of intestinal microbiota in healthy subjects and in patients of Mexican mestizo origin that present with cirrhosis of the liver. Materials and methodsBiochemical liver function parameters (ALT, AST, GGT, BIL-T, etc.) were determined in 23 cirrhotic patients and 21 control subjects. The intestinal microbiota was established through 16S ribosomal RNA gene sequencing. ResultsThe cirrhotic patients had elevated levels of ALT, AST, GGT (105.2±77.7 vs. 20.99±8.5UI/L, 110±68.6 vs. 23.39±5.2, and 119.1±79.1 vs. 19.3±15.2UI/L, respectively), IL-6 (1.64±0.38pg/ml, P<.001), or TNFα (1.78±0.3, P<.05). The intestinal microbiota of the cirrhotic patients was less diverse, compared with that of the control subjects. At the level of the phylum, there was a significant increase in Proteobacteria and Bacteroidetes in the patients with cirrhosis, compared with the controls (6.2 vs. 4.9% and 44 vs. 46%, respectively, P<.01). In contrast, there was a decrease in Firmicutes, Actinobacteria, and Fusobacteria in the cirrhotic patients. There was an increase in the Campylobacter and Gemella families in the cirrhotic patients, whereas Streptococcus and Veillonella had a positive association with serum ALT or AST levels. ConclusionsTo the best of our knowledge, the present study is the first to demonstrate the type of intestinal microbiota in Mexican patients with cirrhosis of the liver. The extension of the findings in a larger cohort of subjects and the metagenome analysis will enable the creation of data that can have relevant treatment implications for this group of patients in Mexico.

Mo1697 - Dietary Fiber and Water Improve Bowel Function and Fecal Microbiota in Healthy Subjects: A Randomized Clinical Trial

Mo1697 - Dietary Fiber and Water Improve Bowel Function and Fecal Microbiota in Healthy Subjects: A Randomized Clinical Trial

1a - Dietary Patterns and Mucosa Associated Colonic Bacterial Microbiota and Stool Microbiota in Healthy Subjects

1a - Dietary Patterns and Mucosa Associated Colonic Bacterial Microbiota and Stool Microbiota in Healthy Subjects

A Concurrent Longitudinal Survey of the Mucosa-Associated Colonic Bacterial Microbiota and Stool Microbiota in Healthy Subjects Shows Preservation of Individual Differences over Time

Introduction: While limited longitudinal studies have assessed the stability of the gut microbiota in fecal samples, there are no published studies to date that have examined the stability of the mucosa-associated microbiota. In this study, we aimed to concurrently characterize the variability in the gut microbiota in mucosal biopsies and stool samples of healthy subjects over a 9 month period. Methods: Healthy control subjects (n=9) were recruited from the community and underwent 4 unprepped flexible sigmoidoscopies at 0, 3, 6, and 9 months. Biopsies were taken of the colonic mucosa during the sigmoidoscopy and stool samples were collected at the same visit. Microbiota was characterized by sequencing of the 16S rDNA on a 454 Roche Titanium platform. Obtained sequences were filtered for quality/chimeras, and were analyzed using Qiime. Unifrac distances were calculated between the samples of the same subject (intra-individual distances), and were compared to the distances from the samples of other subjects (inter-individual distances). Results: Bacterial composition remained relatively stable over time in individual subjects over 9 months; and inter-individual Unifrac distances were higher than intra-individual ones ( 0.714 ± 0.058 vs.0.610 ± 0.085 respectively, p=0.001) for the entire sample set. This significant difference between inter-individual and intra-individual Unifrac distances was preserved for both colonic biopsy samples and for stool samples (p=0.0001 for both). When intra-individual Unifrac distances between stool samples were compared to that of biopsy samples, there was no observed difference between the sample types (0.586 ± 0.628 vs. 0.579 ± 0.076 respectively, p=0.384), suggesting that there is a similar degree of variability in the longitudinal stool samples and the longitudinal biopsy samples of the same individual. However, higher inter-individual Unifrac distances were noted in longitudinal stool samples compared to longitudinal biopsy samples (0.713 ± 0.057 vs. 0.691 ± 0.052 respectively, p=0.0001), suggesting that there is a slightly lower variability within longitudinal biopsy samples of different individuals. Conclusion: Inter-individual variation in the bacterial microbiome is preserved in longitudinal colonic biopsy samples. Time and sampling related variability in the mucosa-associated colonic bacterial microbiome in healthy individuals is not large enough to supercede inter-individual differences.

The Effects of Bowel Preparation on Microbiota-Related Metrics Differ in Health and in Inflammatory Bowel Disease and for the Mucosal and Luminal Microbiota Compartments.

OBJECTIVES:Bowel preparations (BPs) taken before colonoscopy may introduce a confounding effect on the results of gastrointestinal microbiota studies. This study aimed to determine the effect of bowel preparation on the mucosa-associated and luminal colonic microbiota in healthy subjects (HC) and inflammatory bowel disease (IBD) patients.METHODS:Biopsy samples (n=36) and fecal samples (n=30) were collected from 10 HC and 8 IBD subjects pre- and post-BP. 16S rRNA gene was pyrosequenced using 454 Titanium protocols. We compared the differences between the pre- and post-BP samples (i.e., comparisons-across-bowel-prep); we examined the effect of BP on the expected separation of the mucosal vs. the luminal compartments (i.e., comparisons-across-compartments). Last, we compared the baseline differences between the HC vs. IBD groups (a secondary analysis), and examined whether the differences between the HC vs. IBD changed after BP.RESULTS:In comparisons-across-bowel-prep, the Shannon's index (SI) decreased only in the biopsy samples of IBD subjects post-BP (P=0.025) and phylogenetic diversity-whole tree (PD-WT) metric decreased in biopsy samples of HC subjects post-BP (P=0.021). In secondary comparisons, the subtle differences between the fecal samples of the HC vs. IBD groups, in terms of evenness and the SI, were not apparent post-BP. In terms of β-diversity, in comparisons-across-bowel-prep, the proportion of shared operational taxonomic units (OTUs) in pre- and post-BP samples was low (~30%) and unweighted Unifrac distances between pre- and post-BP specimens ranged from 0.52 to 0.66. HC biopsies were affected more than IBD biopsies with BP (P=0.004). In comparisons-across-compartments, the proportion of shared OTUs between biopsy and fecal samples increased and Unifrac distances decreased post-BP in IBD subjects, reducing the differences between the mucosal and luminal compartments of the gut microbiota. Interindividual differences in Unifrac distances were preserved even with BP effects, although the effects were greater on weighted Unifrac distances. Bacteroidetes and its subtypes increased post-BP in both the luminal and mucosal compartments.CONCLUSIONS:Bowel preparations affect the composition and diversity of the fecal and luminal microbiota in the short term, introducing potential bias into experiments examining the gut microbiota. The magnitude of the effect of BP is not greater than that of interindividual variation. Both the luminal and mucosal compartments of the gut microbiota get affected, and samples from controls and IBD subjects may get affected differently. Studies of the colonic microbiota should take into account the direction and the magnitude of the change introduced by BP during the design stage of the experiments, and consider sample sizes so that potential bias is minimized.

The relationship between faecal-associated and mucosal-associated microbiota in irritable bowel syndrome patients and healthy subjects.

The faecal-associated microbiota is commonly seen as a surrogate of the mucosal-associated microbiota. However, previous studies indicate that they are different. Furthermore, analyses of the mucosal microbiota are commonly done after standard bowel cleansing, affecting the microbial composition. To compare the mucosal-associated microbiota, obtained from unprepared colon, with faecal-associated microbiota in healthy subjects and irritable bowel syndrome (IBS) patients. Faecal and mucosal biopsies were obtained from 33 IBS patients and 16 healthy controls. Of IBS patients, 49% belonged to the diarrhoea-predominant subgroup and 80% suffered from IBS symptoms during at least 5 years. Biopsies were collected from unprepared sigmoid colon and faecal samples a day before colonoscopy. Microbiota analyses were performed with a phylogenetic microarray and redundancy discriminant analysis. The composition of the mucosal- and the faecal-associated microbiota in unprepared sigmoid colon differs significantly (P = 0.002). Clinical characteristics of IBS did not correlate with this difference. Bacteroidetes dominate the mucosal-associated microbiota. Firmicutes, Actinobacteria and Proteobacteria dominate the faecal-associated microbiota. Healthy subjects had a significantly higher (P < 0.005) abundance (1.9%) of the bacterial group uncultured Clostridiales I in the mucosal-associated microbiota than IBS patients (0.3%). Bacterial diversity was higher in faecal- compared with mucosal-associated microbiota in IBS patients (P < 0.005). No differences were found in healthy subjects. Differences in the mucosal-associated microbiota between healthy individuals and IBS patients are minimal (one bacterial group) compared to differences in the faecal microbiota of both groups (53 bacterial groups). Microbial aberrations characterising IBS are more pronounced in the faeces than in the mucosa.

Tu2024 A Comparison of the Microbiota in Healthy Subjects and Patients With Chronic Constipation

Tu2024 A Comparison of the Microbiota in Healthy Subjects and Patients With Chronic Constipation

Sa1988 The Effect of Bowel Preparation on the Colonic Microbiota in Healthy Subjects and in Patients With Inflammatory Bowel Disease

Background and aims: Microbe and host interaction occurs primarily along mucosal surfaces of the gastrointestinal tract. Various studies reported high inter-subject variability of a uniformly distributed microbiota in colonic biopsies sampled along the colon that differed from the feces (Echburg et al. Science 2005, Zoetendal et al. Appl Environ Microbiol 2002) The aim of the study was to investigate intra-individual differences between small and large bowel biopsies based on their microbiota composition, clustering and diversity. Methods: We included patients scheduled for colonoscopy for diagnostic purposes. Biopsies from healthy terminal ileum and ascending colon were sampled with a standard biopsy forceps and snap frozen in liquid nitrogen. Microbiota composition based on 16S rRNA variability was determined using the phylogenetic microarray for the Human Intestinal Tract (HITChip) (Rajilic-Stojanovic, M. et al, Environ. Microbiol 2009). Results: We included 8 subjects: median age was 65 years (IQR 51-72), 7 of them were male. All patients had normal ileal and colonic mucosa. No significant differences were found in the comparison of 22 phylum/ order-like and 130 genus-like groups included in HITChip analyses in ileal versus colonic mucosal biopsies. The average Pearson correlation for intra-individual comparisons was: r= 0.88±0.13. Samples clustered by host and not by sampling location (inter-individual Pearson correlation in colon and ileum samples: r= 0.88±0.04 and r= 0.87±0.06 respectively, p= 0.86), and were comparable according to: diversity, eveness and richness in colon vs ileum respectively. Conclusion: Small and large bowel biopsies sampled from the terminal ileum or the ascending colon show similar results in clustering, diversity, evenness and richness of the host's microbiota. These findings indicate that the ileocecal valve does not separate the ileal mucosal microbiota from that of the proximal colon.

Increase in fecal primary bile acids and dysbiosis in patients with diarrhea‐predominant irritable bowel syndrome

Irritable bowel syndrome (IBS) is a multifactorial disease for which a dysbiosis of the gut microbiota has been described. Bile acids (BA) could play a role as they are endogenous laxatives and are metabolized by gut microbiota. We compared fecal BA profiles and microbiota in healthy subjects (HS) and patients with diarrhea-predominant IBS (IBS-D), and we searched for an association with symptoms. Clinical features and stool samples were collected in IBS-D patients and HS. Fecal BA profiles were generated using HPLC coupled to tandem mass spectrometry. The fecal microbiota composition was assessed by q-PCR targeting dominant bacterial groups and species implicated in BA transformation. Fourteen IBS-D patients and 18 HS were included. The two groups were comparable in terms of age and sex. The percentage of fecal primary BA was significantly higher in IBS-D patients than in HS, and it was significantly correlated with stool consistency and frequency. Fecal counts of all bacteria, lactobacillus, coccoides, leptum and Faecalibacterium prausnitzii were similar. There was a significant increase of Escherichia coli and a significant decrease of leptum and bifidobacterium in IBS-D patients. We report an increase of primary BA in the feces of IBS-D patients compared to HS, correlated with stool consistency and frequency. A dysbiosis of different bacterial groups was detected, some of them involved in BA transformation. As the gut microbiota is the exclusive pathway to transform primary into secondary BA, this suggests a functional consequence of dysbiosis, leading to lower BA transformation.

Effects of Mouth Wash with Hot Caffeine Solution on the Oral Microbiota in Healthy Subjects

Effects of Mouth Wash with Hot Caffeine Solution on the Oral Microbiota in Healthy Subjects

Intestinal Microbiota in Healthy Adults: Temporal Analysis Reveals Individual and Common Core and Relation to Intestinal Symptoms

BackgroundWhile our knowledge of the intestinal microbiota during disease is accumulating, basic information of the microbiota in healthy subjects is still scarce. The aim of this study was to characterize the intestinal microbiota of healthy adults and specifically address its temporal stability, core microbiota and relation with intestinal symptoms. We carried out a longitudinal study by following a set of 15 healthy Finnish subjects for seven weeks and regularly assessed their intestinal bacteria and archaea with the Human Intestinal Tract (HIT)Chip, a phylogenetic microarray, in conjunction with qPCR analyses. The health perception and occurrence of intestinal symptoms was recorded by questionnaire at each sampling point.Principal FindingsA high overall temporal stability of the microbiota was observed. Five subjects showed transient microbiota destabilization, which correlated not only with the intake of antibiotics but also with overseas travelling and temporary illness, expanding the hitherto known factors affecting the intestinal microbiota. We identified significant correlations between the microbiota and common intestinal symptoms, including abdominal pain and bloating. The most striking finding was the inverse correlation between Bifidobacteria and abdominal pain: subjects who experienced pain had over five-fold less Bifidobacteria compared to those without pain. Finally, a novel computational approach was used to define the common core microbiota, highlighting the role of the analysis depth in finding the phylogenetic core and estimating its size. The in-depth analysis suggested that we share a substantial number of our intestinal phylotypes but as they represent highly variable proportions of the total community, many of them often remain undetected.Conclusions/SignificanceA global and high-resolution microbiota analysis was carried out to determine the temporal stability, the associations with intestinal symptoms, and the individual and common core microbiota in healthy adults. The findings provide new approaches to define intestinal health and to further characterize the microbial communities inhabiting the human gut.