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Results for “Intestinal microbiota”

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PubMed2002

Trypsin mediates growth phase-dependent transcriptional tegulation of genes involved in biosynthesis of ruminococcin A, a lantibiotic produced by a Ruminococcus gnavus strain from a human intestinal microbiota.

Ruminococcin A (RumA) is a trypsin-dependent lantibiotic produced by Ruminococcus gnavus E1, a gram-positive strict anaerobic strain isolated from a human intestinal microbiota. A 12.8-kb region from R. gnavus E1 chromosome, containing the biosynthetic gene cluster of RumA, has been cloned and sequenced. It consisted of 13 open reading frames, organized in three operons with predicted functions in lantibiotic biosynthesis, signal transduction regulation, and immunity. One unusual feature of the locus is the presence of three almost identical structural genes, all of them encoding the RumA precursor. In order to determine the role of trypsin in RumA production, the transcription of the rum genes has been investigated under inducing and noninducing conditions. Trypsin activity is needed for the growth phase-dependent transcriptional activation of RumA operons. Our results suggest that bacteriocin production by R. gnavus E1 is controlled through a complex signaling mechanism involving the proteolytic processing of a putative extracellular inducer-peptide by trypsin, a specific environmental cue of the digestive ecosystem.

Amino Acid Sequence↗

PubMed2005

1H nuclear magnetic resonance spectroscopy-based studies of the metabolism of food-borne carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline by human intestinal microbiota.

2-Amino-3-methylimidazo[4,5-f]quinoline (IQ) is a mutagenic/carcinogenic compound formed from meat and fish during cooking. Following ingestion, IQ is metabolized mainly by liver xenobiotic-metabolizing enzymes, but intestinal bacteria may also contribute to its biotransformation. The aim of this study was to investigate the metabolism of IQ by the human intestinal microbiota. Following incubation of IQ (200 microM) under anoxic conditions with 100-fold dilutions of stools freshly collected from three healthy volunteers, we quantified residual IQ by high-pressure liquid chromatography (HPLC) analysis and characterized the production of IQ metabolites by in situ (1)H nuclear magnetic resonance ((1)H-NMR) spectroscopic analysis of crude incubation media. In addition, we looked for IQ-degrading bacteria by screening collection strains and by isolating new strains from the cecal contents of human-microbiota-associated rats gavaged with IQ on a regular basis. HPLC and (1)H-NMR analyses showed that the three human microbiota degraded IQ with different efficiencies (range, 50 to 91% after 72 h of incubation) and converted it into a unique derivative, namely, 7-hydroxy-IQ. We found 10 bacterial strains that were able to perform this reaction: Bacteroides thetaiotaomicron (n = 2), Clostridium clostridiiforme (n = 3), Clostridium perfringens (n = 1), and Escherichia coli (n = 4). On the whole, our results indicate that bacteria belonging to the predominant communities of the human intestine are able to produce 7-hydroxy-IQ from IQ. They also suggest interindividual differences in the ability to perform this reaction. Whether it is a metabolic activation is still a matter of debate, since 7-hydroxy-IQ has been shown to be a direct-acting mutagen in the Ames assay but not carcinogenic in laboratory rodents.

Adult↗

PubMed2005

Effects of zinc oxide and Enterococcus faecium SF68 dietary supplementation on the performance, intestinal microbiota and immune status of weaned piglets.

The objective of this study was to determine the effects of zinc oxide (ZnO) and the probiotic Enterococcus faecium SF68 (Cylactin) dietary supplementation on the performance, intestinal microbiota and immune parameters of the weaned piglet reared under commercial conditions. The diets were devoid of antibiotic growth promoters (AGP). Two hundred and eight crossbred piglets were allocated to a 2 x 2 factorial experiment involving two levels of zinc oxide supplementation (0 or 3100 mg ZnO/kg feed), and two levels of E. faecium SF68 supplementation (0 or 1.4 x 10(9)CFU/kg feed (Cylactin ME10)). The diets were offered ad libitum for 20 days post-weaning. Piglet performance was assessed by calculating average daily gain (ADG), average daily feed intake (ADFI) and feed conversion ratio (FCR) on a pen basis. In addition, components of the distal ileal digesta, tissue-associated and mesenteric lymph node (MLN) bacterial populations were enumerated and serum immunoglobulin G (IgG) and intestinal immunoglobulin A (IgA) concentrations were determined on days 6 and 20 post-weaning. Regression analysis was used to determine the relationship between the bacterial populations at the different sites. Supplementation of the post-weaning diet with either ZnO or E. faecium SF68 did not affect piglet performance. E. faecium SF68 did not affect gastrointestinal bacterial populations but did tend to reduce serum IgG (P<0.1) on day 20. Zinc oxide reduced anaerobic (P<0.05) and tended to decrease lactic acid (P<0.1) bacterial translocation to the MLN, and tended to increase intestinal IgA concentration (P<0.1) on day 20. Generally, luminal bacterial populations were found to be poor predictors of tissue-associated or MLN populations. ZnO and E. faecium SF68 dietary supplementation were ineffective under these trial conditions. Further investigations into the possible immunomodulator role of dietary ZnO are warranted.

Animals↗

PubMed2006

Effects of Lactococcus lactis on composition of intestinal microbiota: role of nisin.

This study examined the ability of (i) pure nisin, (ii) nisin-producing Lactococcus lactis strain CHCC5826, and (iii) the non-nisin-producing L. lactis strain CHCH2862 to affect the composition of the intestinal microbiota of human flora-associated rats. The presence of both the nisin-producing and the non-nisin-producing L. lactis strains significantly increased the number of Bifidobacterium cells in fecal samples during the first 8 days but decreased the number of enterococci/streptococci in duodenum, ileum, cecum, and colon samples as detected by selective cultivation. No significant changes in the rat fecal microbiota were observed after dosage with nisin. Pearson cluster analysis of denaturing gradient gel electrophoresis profiles of the 16S rRNA genes present in the fecal microbial population revealed that the microbiota of animals dosed with either of the two L. lactis strains were different from that of control animals dosed with saline. However, profiles of the microbiota from animals dosed with nisin did not differ from the controls. The concentrations of nisin estimated by competitive enzyme-linked immunosorbent assay (ELISA) were approximately 10-fold higher in the small intestine and 200-fold higher in feces than the corresponding concentrations estimated by a biological assay. This indicates that nisin was degraded or inactivated in the gastrointestinal tract, since fragments of this bacteriocin are detected by ELISA while an intact molecule is needed to retain biological activity.

Agar↗

PubMed2005

Xanthohumol does not affect the composition of rat intestinal microbiota.

Xanthohumol (XN), a prenylated chalcone, has been proposed to have beneficial effects on human health, including antimicrobial activity. To clarify whether the exposure to XN has an impact on the composition of the intestinal microbiota, 100 mg XN/kg body weight was given daily to rats for 4 wk. Diversity of the fecal microbial community was analyzed using PCR-DGGE. Although intact XN was detected in the feces of the rats at a concentration of up to 2.3 mg/g fecal dry weight, major shifts in the PCR-DGGE patterns in response to this flavonoid were not observed. The similarity index decreased slightly from 70 to 62% for the XN-treated rats and from 71 to 63% for the untreated animals. Thus, changes in the rat fecal microbiota observed in the course of the XN application are most likely due to intraindividual variability. However, the water content of the feces increased significantly during the XN treatment period.

Animals↗

PubMed2005

New therapeutic strategy for combating the increasing burden of allergic disease: Probiotics-A Nutrition, Allergy, Mucosal Immunology and Intestinal Microbiota (NAMI) Research Group report.

The dietary approach to reducing the risk of atopic diseases in infancy is evolving from passive allergen avoidance to active stimulation of the immature immune system, the aim of which is to support the establishment of tolerance. The intestinal mucosa and the mucosa-associated immune system are the primary loci of allergen contact and induction of immune responsiveness. In this review we discuss cross-talk between the intestinal microbiota and the host as it pertains to healthy immunologic maturation. Understanding these complex phenomena provides the rationale for the use of probiotics in reducing the risk and nutritional management of atopic disease.

Animals↗

PubMed2006

Influencing health through intestinal microbiota modulation and probiotics.

Science has progressed fast in providing answers to probiotic health benefits to the consumers. This symposium also proves that progress is fast. However, several challenges still need to be solved and more effective strains and strain combinations discovered. This will pave the way from good probiotics to specific products for clearly identified target populations. The intestinal microbiota and its interaction(s) with probiotics challenges researchers to turn to the next new page to discover new approaches and treatment modalities that utilize probiotics as means of providing good nutrition with clear health benefits to all consumers.

Clinical Trials as Topic↗

PubMed2026

[Intestinal microbiota alterations after digestive tract reconstruction surgery and their impacts on host physiology].

The gut microbiota, acknowledged as the human body's 'second genome', plays a pivotal role in maintaining health. Digestive tract reconstruction surgery profoundly alters the anatomical structure and physiological environment of the gastrointestinal tract, thereby inducing significant shifts in the intestinal microbiota. These microbial changes subsequently influence host physiological functions through metabolic, immune, neuroendocrine, and other pathways. For instance, Roux-en-Y gastric bypass surgery enriches short-chain fatty acid(SCFA)-producing Bacteroides, improving systemic insulin sensitivity. Conversely, pancreaticoduodenectomy leads to a marked enrichment of potential pathobionts such as Klebsiella and Clostridium, which may elevate the risk of infections and tumor recurrence. This review comprehensively summarizes the characteristic changes in the gut microbiota following various digestive tract reconstruction procedures and discusses their multifaceted impacts on host physiology, aiming to provide insights for future experimental research and clinical practice.

Humans↗

PubMed2005

Effects of probiotics on the composition of the intestinal microbiota following antibiotic therapy.

The effects of probiotic supplementation on the intestinal re-growth microbiota following antibiotic therapy were studied in a double-blind placebo-controlled study. In the placebo group, numbers of facultative anaerobes and enterobacteria increased significantly, and at day 35 the numbers were significantly higher in the placebo group than in the active group; in the active group, the numbers of bacteroides increased significantly. Although the numbers of enterococci in both groups did not change, in the placebo group the number of patients harbouring antibiotic-resistant enterococci post therapy increased significantly. There was no change in the incidence rate of antibiotic resistance among the patients in the probiotic group.

Anti-Bacterial Agents↗

PubMed1997

Effect of the addition of Peptostreptococcus productus ATCC35244 on the gastro-intestinal microbiota and its activity, as simulated in an in vitro simulator of the human gastro-intestinal tract.

Peptostreptococcus productus ATCC35244, a reductive acetogenic strain, was added daily over 9 successive days to the fourth vessel (ascending colon) of the SHIME, a six-stage reactor system simulating the in vivo continuous culture conditions of the human gastro-intestinal tract. Final numbers of organisms (cfu)/ml reactor contents (c) were attained such that log10c = 6.9 +/- 0.1. The addition caused the CH4 production to decrease below the detection limit while total gas and CO2 production in the fifth (transverse colon) and sixth reactor (descending colon) were lowered and the acetic acid concentration was augmented. Ending the supplementation caused CH4 production to re-establish within 4 days, while CO2 production increased much more slowly. The concentration of acetic acid only started to decrease after 7 days. The results indicate that P. productus, upon regular administration, is able to compete with methanogens for H2 in the gastro-intestinal microbial ecosystem because of its reductive acetogenic character.

Acetic Acid↗

PubMed2006

Characterization of intestinal microbiota and response to dietary virginiamycin supplementation in the broiler chicken.

The inclusion of antibiotic growth promoters, such as virginiamycin, at subtherapeutic levels in poultry feeds has a positive effect on health and growth characteristics, possibly due to beneficial effects on the host gastrointestinal microbiota. To improve our understanding of the chicken gastrointestinal microbiota and the effect of virginiamycin on its composition, we characterized the bacteria found in five different gastrointestinal tract locations (duodenal loop, mid-jejunum, proximal ileum, ileocecal junction, and cecum) in 47-day-old chickens that were fed diets excluding or including virginiamycin throughout the production cycle. Ten libraries (five gastrointestinal tract locations from two groups of birds) of approximately 555-bp chaperonin 60 PCR products were prepared, and 10,932 cloned sequences were analyzed. A total of 370 distinct cpn60 sequences were identified, which ranged in frequency of recovery from 1 to 2,872. The small intestinal libraries were dominated by sequences from the Lactobacillales (90% of sequences), while the cecum libraries were more diverse and included members of the Clostridiales (68%), Lactobacillales (25%), and Bacteroidetes (6%). To assess the effects of virginiamycin on the gastrointestinal microbiota, 15 bacterial targets were enumerated using quantitative, real-time PCR. Virginiamycin was associated with increased abundance of many of the targets in the proximal gastrointestinal tract (duodenal loop to proximal ileum), with fewer targets affected in the distal regions (ileocecal junction and cecum). These findings provide improved profiling of the composition of the chicken intestinal microbiota and indicate that microbial responses to virginiamycin are most significant in the proximal small intestine.

Animals↗

PubMed2002

Effects of rifaximin administration on the intestinal microbiota in patients with ulcerative colitis.

The effect of rifaximin on the intestinal bacterial population was studied in a clinical trial. Twelve patients with ulcerative colitis were administered rifaximin 1800 mg/day in 3 treatment periods of 10 days, each followed by 25 days of wash-out. Fecal samples were collected at the beginning and at the end of each treatment period to perform microbiological examinations. Titer variations of enterococci, coliforms, lactobacilli, bifidobacteria, Bacteroides spp., and Clostridium perfringens as well as their susceptibility to rifaximin during the different phases of the study were evaluated. The presence of Candida spp. was also monitored. After each wash-out period, concentrations of the intestinal microbial groups tested returned to initial values, showing that the administration of high doses of rifaximin does not significantly modify the colonic microbiota. Rifaximin-resistant isolates were also found, particularly in bacteria belonging to Bifidobacterium genus, included as probiotics in several fermented foods and in pharmaceutical preparations.

Adult↗

PubMed1989

Effect of ampicillin-induced alterations in murine intestinal microbiota on the survival and competition of environmentally released pseudomonads.

The environmental release of genetically altered microorganisms has prompted the investigation of their potential health effects by the employment of other-than-human models. Although direct health effects are addressed, this investigation examines primarily some potential indirect health effects associated with environmentally released microorganisms. Indirect effects examined include colonization of the gastrointestinal tract, competition with the resident microbiota, and translocation of the dosed microorganisms to other organs. Pseudomonads used in this study were isolated from a commercial product marketed for environmental PCB degradation. When mice were dosed by gavage with approximately 10(9) ampicillin-resistant pseudomonads, an increase in recovery from the intestinal tract, as compared to untreated animals, was observed 48 hr after dosing. Intestinal survival of Pseudomonas aeruginosa strain BC16 was enhanced 1000-fold and that of P. maltophilia strain BC6, 10-fold. Strains BC17 and BC18 were unaffected. Ampicillin treatment had a significant effect on the relative number of microbiota in the intestine, by selecting primarily for the facultative species. The lactose-fermenting enterobacteria, obligately anaerobic predominantly Gram-negative rods, and total aerobic and anaerobic populations were monitored in the presence and absence of the PCB-degrading pseudomonad. P. aeruginosa strain BC17 and P. maltophilia strain BC6 had a dose effect (p less than 0.05) on the total aerobic and anaerobic populations as well as the lactose-fermenting enterobacteria. These results are similar to those for the mouse isolate control, strain PAMG. P. aeruginosa strain BC18 had a dose effect (p less than 0.05) on the total anaerobic population, including the obligately anaerobic Gram-negative bacilli. No translocation of the dosed strains to the liver, spleen, or lung was observed 48 hr after dosing.

Ampicillin↗

PubMed2005

Intestinal microbiota.

Explore the source record for details and available documents.

Bacterial Physiological Phenomena↗

PubMed2006

Metabolism of the food-associated carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine by human intestinal microbiota.

2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine is a putative human carcinogenic heterocyclic aromatic amine formed from meat and fish during cooking. Although the formation of hazardous PhIP metabolites by mammalian enzymes is well-documented, nothing is known about the PhIP transformation potency of human intestinal bacteria. In this study, the in vitro metabolism of PhIP by human fecal samples was investigated. Following anaerobic incubation of PhIP with stools freshly collected from six healthy volunteers, we found that PhIP was extensively transformed by the human intestinal bacteria. HPLC analysis showed that the six human fecal microbiota transformed PhIP with efficiencies from 47 to 95% after 72 h incubation, resulting in one major derivative. ESI-MS/MS, HRMS, 1D (1H, 13C, DEPT) and 2D (gCOSY, gTOCSY, gHMBC, gHSQC) NMR, and IC analysis elucidated the complete chemical identity of the microbial PhIP metabolite as 7-hydroxy-5-methyl-3-phenyl-6,7,8,9-tetrahydropyrido[3',2':4,5]imidazo[1,2-a]pyrimidin-5-ium chloride. At present, no information is available about the biological activity of this newly discovered bacterial PhIP metabolite. Our findings however suggest that bacteria derived from the human intestine play a key role in the activation or detoxification of PhIP, a digestive fate ignored so far in risk assessments. Moreover, the variation in transformation efficiency between the human microbiota indicates interindividual differences in the ability to convert PhIP. This may predict individual susceptibility to carcinogenic risk from this suspected dietary carcinogen.

Adult↗

PubMed2006

Dendritic cells in the recognition of intestinal microbiota.

Mucosal dendritic cells (DCs) constantly survey the luminal microenvironment which contains commensal microbiota and potentially harmful organisms regulating pathogen recognition and adaptive as well as innate defense activation. Distinct mechanisms are beginning to emerge by which intestinal antigen sampling and handling is achieved ensuring specificity and contributing to redundancy in pathogen detection. Distinct DC subsets are associated with these mechanisms and regulate specific innate or adaptive immune responses to help distinguish between commensal microbiota, pathogens and self antigens. Understanding DC biology in the mucosal immune system may contribute to the unraveling of infection routes of intestinal pathogens and may aid in developing novel vaccines and therapeutic strategies for the treatment of infectious and inflammatory diseases.

Animals↗

PubMed2005

Isoflavones and functional foods alter the dominant intestinal microbiota in postmenopausal women.

Dietary phytoestrogens, such as isoflavones, are used as food additives to prevent menopause-related disorders. In addition to other factors, their bioavailability strongly depends on the activity of intestinal bacteria but the underlying interactions remain poorly understood. A randomized, double-blind, placebo-controlled study was undertaken with 39 postmenopausal women to characterize changes in the dominant microbial communities of the intestinal tract after 2 mo of isoflavone supplementation with and without pro- or prebiotic. The diversity and composition of the dominant microbiota were analyzed by temporal temperature-gradient gel electrophoresis (TTGE) and fluorescent in situ hybridization. Isoflavones alone stimulated dominant microorganisms of the Clostridium coccoides-Eubacterium rectale cluster, Lactobacillus-Enterococcus group, Faecalibacterium prausnitzii subgroup, and Bifidobacterium genus. The stimulation of the Clostridium coccoides-Eubacterium rectale cluster depended on the women's equol excretion and was transient, with the exception of a prolonged bifidogenic effect. Lasting changes in the diversity of the dominant species were also observed. The probiotic strain supplied could be detected by TTGE during its passage through the intestinal tract, and ingestion of fructooligosaccharides triggered a marked and specific bifidogenic effect. In conclusion, this is the first human study that shows changes in the diversity and composition of dominant bacterial communities in response to dietary supplementation with hormone-related compounds combined with functional foods.

Aged↗

PubMed2002

Detection and identification of Vibrio scophthalmi in the intestinal microbiota of fish and evaluation of host specificity.

AIMS: To develop a species-specific probe (VSV3) for the detection of Vibrio scophthalmi in fish intestine and to apply this probe to study the host specificity of V. scophthalmi. METHODS AND RESULTS: A specific probe (VSV3) based on the variable region V3 of the 16S rRNA gene (rDNA) was designed. Its specificity was tested by DNA-DNA hybridization and by colony hybridization. No cross-hybridization was found. The sensitivity of the probe was tested both by DNA-DNA hybridization and by colony hybridization. The detection limit of V. scophthalmi 16S rDNA was 150 pg or 10 cfu. Vibrio scophthalmi cells were detected in experimental samples constituted by mixed cultures when present in proportions of 1 : 10 and 1 : 100. The VSV3 probe also proved to be reliable for the detection of V. scophthalmi in samples of fish intestine. CONCLUSIONS: The VSV3 probe can be used for the detection of V. scophthalmi in colony hybridization or DNA-DNA hybridization of amplified 16S rDNA. Preliminary results indicate that V. scophthalmi may present certain host specificity for turbot. SIGNIFICANCE AND IMPACT OF THE STUDY: The VSV3 probe provides a useful tool for ecological studies.

Animals↗