Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “microbiota”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed2005

Gut microbiota and parasite transmission by insect vectors.

In the gut of some insect vectors, parasites ingested with the bloodmeal decrease in number before coming into contact with host tissues. Many factors could be responsible for this reduction in parasite number but the potentially important role of the large communities of naturally occurring microorganisms that exist alongside the newly ingested parasites in the vector midgut has been largely overlooked. Some previous reports exist of the inhibition of parasite development by vector gut microbiota and of the killing of Trypanosoma cruzi and Plasmodium spp. by prodigiosin produced by bacteria. Based on this evidence, we believe that the microbiota present in the midgut of vector insects could have important roles as determinants of parasite survival and development in insect vector hosts and, therefore, contribute to the modulation of vector competence for many important diseases.

Animals↗
PubMed2006

Lactobacillus paracasei A survives gastrointestinal passage and affects the fecal microbiota of healthy infants.

This study focuses on the potentiality of a putative probiotic strain, Lactobacillus paracasei A, to survive gastrointestinal (GI) passage and modulate the resident microbiota of healthy infants. In a placebo-controlled study, 26 children aged 12-24 months received 100 g/day of either fermented milk containing strain A or pasteurized yogurt for four weeks. Fecal samples were analyzed before starting the administration, after 1, 3 and 4 weeks of consumption and after washout. The fate of strain A was followed by means of a newly developed PCR targeting a strain-specific genomic marker. The composition and dynamics of fecal microbial communities during the study were analyzed by culturing on selective media and by the PCR-denaturing gradient gel electrophoresis (DGGE) technique using universal and group-specific (Lactobacillus and Bifidobacterium) primers. The variation in enzymatic activities in infant feces during probiotic consumption was also analyzed. Strain A survived in fecal samples in most (92%) of the infants examined after 1 week of consumption, and temporarily dominated the intestinal Lactobacillus community. The administration of L. paracasei A led to a significant increment in the Lactobacillus population, while a moderate effect upon the main bacterial groups in the GI ecosystem was observed. Strain A also affected the diversity of the Lactobacillus and Bifidobacterium populations. The fecal bacterial structure of 1 - 2-year-old infants seems to combine neonate and adult-like features. The microbiota of these subjects promptly responded to probiotic consumption, later restoring the endogenous equilibrium.

Cultured Milk Products↗
PubMed2005

Acquired antimicrobial resistance in the intestinal microbiota of diverse cat populations.

The aim of this study was to investigate the prevalence of acquired antimicrobial resistance in the resident intestinal microbiota of cats and to identify significant differences between various cat populations. Escherichia coli, Enterococcus faecalis, E. faecium and Streptococcus canis were isolated as faecal indicator bacteria from rectal swabs of 47 individually owned cats, 47 cattery cats and 18 hospitalised cats, and submitted through antimicrobial sensitivity tests. The results revealed that bacteria isolated from hospitalised and/or cattery cats were more frequently resistant than those from individually owned cats. E. coli isolates from hospitalised cats were particularly resistant to ampicillin, tetracycline and sulfonamide. Both enterococci and streptococci showed high resistance to tetracycline and in somewhat lesser extent to erythromycin and tylosin. Most E. faecium isolates were resistant to lincomycin and penicillin. One E. faecalis as well as one E. faecium isolate from hospitalised cats showed 'high-level resistance' (MIC > 500 microg/ml) against gentamicin, a commonly used antimicrobial agent in case of human enterococcal infections. The results of this research demonstrate that the extent of acquired antimicrobial resistance in the intestinal microbiota of cats depends on the social environment of the investigated population. It is obvious that the flora of healthy cats may act as a reservoir of resistance genes.

Animals↗
PubMed2006

Use of axenic animals in studying the adaptation of mammals to their commensal intestinal microbiota.

Vertebrates are essentially born germ-free but normally acquire a complex intestinal microbiota soon after birth. Most of these organisms are non-pathogenic to immunocompetent hosts; in fact, many are beneficial, supplying vitamins for host nutrition and filling the available microbiological niche to limit access and consequent pathology when pathogens are encountered. Thus, mammalian health depends on mutualism between host and flora. This is evident in inflammatory conditions such as inflammatory bowel disease, where aberrant responses to microbiota can result in host pathology. Studies with axenic (germ-free) or deliberately colonised animals have revealed that commensal organisms are required for the development of a fully functional immune system and affect many physiological processes within the host. Here, we describe the technical requirements for raising and maintaining axenic and gnotobiotic animals, and highlight the extreme diversity of changes within and beyond the immune system that occur when a germ-free animal is colonized with commensal bacteria.

Animals↗
PubMed2006

Leeches and their microbiota: naturally simple symbiosis models.

Strictly blood-feeding leeches and their limited microbiota provide natural and powerful model systems to examine symbiosis. Blood is devoid of essential nutrients and it is thought that symbiotic bacteria synthesize these for the host. In this review, three distinct leech-microbe associations are described: (i) the mycetome, which is the large symbiont-containing organ associated with the esophagus; (ii) the nephridia and bladders that form the excretory system; and (iii) the digestive tract, where two bacterial species dominate the microbiota. The current knowledge and features of leech biology that promote the investigation of interspecific interactions (host-microbe and microbe-microbe) and their evolution are highlighted.

Animals↗
PubMed2006

Assembly of the human intestinal microbiota.

Complex microbial ecosystems occupy the skin, mucosa and alimentary tract of all mammals, including humans. Recent advances have highlighted the tremendous diversity of these microbial communities and their importance to host physiology, but questions remain about the ecological processes that establish and maintain the microbiota throughout life. The prevailing view, that the gastrointestinal microbiota of adult humans is a climax community comprised of the superior competitors for a stable set of niches, does not account for all of the experimental data. We argue here that the unique history of each community and intrinsic temporal dynamics also influence the structure of human intestinal communities.

Humans↗
PubMed2000

Desipramine changes salivary gland function, oral microbiota, and oral health in rats.

Tricyclic antidepressants are still a dominating group of psychotherapeutic drugs used in the treatment of depression. Oral dryness is one of their major side-effects, leading in humans to increased oral disease and dysfunction of speech, chewing, swallowing and taste. We previously reported that the tricyclic antidepressant desipramine desensitizes beta-adrenergic signal transduction in salivary glands. In this study, we evaluated the effects of this treatment on parotid and submandibular gland function, oral microbiota, and oral health in rats. Total protein secretion and salivary alpha-amylase was not affected by treatment, while cellular alpha-amylase and the content of epidermal growth factor was depressed. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed increased secretion for proline-rich proteins and glycoproteins. Surprisingly, flow rates were temporarily increased. These alterations in salivary gland function may partially explain the observed changes in oral microbiota and the increased incidence of gingivitis. Under other nutritional conditions, desipramine might have more severe impacts on oral health.

Adrenergic Uptake Inhibitors↗
PubMed1999

Application of denaturant gradient gel electrophoresis for the analysis of the porcine gastrointestinal microbiota.

The porcine gastrointestinal tract (GIT) microbiota has been studied to increase production efficiency, improve product quality, and help attempt to reduce disease. During the developmental period from birth through weaning, the intestinal microbiota undergoes a rapid ecological succession. There is interest in developing a monitoring technique that allows for analysis of bacterial population levels and shifts within the pig intestine. The objective of this study was to determine if denaturant gradient gel electrophoresis (DGGE) could be effectively applied to measure changes in bacterial populations of the pig GIT, as influenced by age, diet or compartment. Bacterial genetic diversity was determined using DGGE analysis of the V3 region of 16S rDNA PCR products (approximately 200 bp) obtained from primers specific for the domain Bacteria. Protocol development included optimization of: DNA extraction procedures, PCR amplification, removal of PCR artifacts, and optimization of gel preparation and image capture. DGGE analysis revealed diverse bacterial populations between pigs of different ages and among individual gut compartments. Comparison of fecal DNA from different aged pigs revealed several unique PCR product bands indicating the presence of unique bacterial populations. Comparison of different gut compartments demonstrated that bacterial populations were most similar (C, value > 50%) within a single compartment and between adjacent ones. Thus, DGGE can be used to examine bacterial diversity and population shifts in the pig GIT.

Aging↗
PubMed1999

The effect of probiotic strains on the microbiota of the Simulator of the Human Intestinal Microbial Ecosystem (SHIME).

The aim of the present work was to study five potential probiotic strains (Lactobacillus plantarum, two strains of L. paracasei subsp. paracasei, L. rhamnosus and Bifidobacterium sp.) comparatively in the Simulator of the Human Intestinal Microbial Ecosystem (SHIME) in vitro model, and to evaluate this model as a tool in the screening and selection of probiotic bacteria. The impact of the strains on the composition of microbiota and its metabolic activities (production of lactic acid and short-chain fatty acids) was studied. Changes in composition of the microbiota become apparent as a result of probiotic treatment. A marked, but temporary, increase was noted in the number of lactic acid bacteria and bifidobacteria. The profiles of D(-) and L(+) isomers of lactic acid detected in the SHIME after addition of probiotic strains corresponded well to those that are produced in pure culture conditions. The numbers of enterobacteriaceae decreased markedly and those of clostridia detectably during the intervention, while the enterococci tended to increase after the treatment. This pattern was similar in the reactors representing both the small and large intestine in the model. The changes in short-chain fatty acids were small, and no definite trend was observed.

Bifidobacterium↗
PubMed2001

Effects of probiotic administration upon the composition and enzymatic activity of human fecal microbiota in patients with irritable bowel syndrome or functional diarrhea.

In a clinical trial, 10 patients suffering from irritable bowel syndrome or functional diarrhea were administered the probiotic preparation VSL-3. Preliminary results indicated that administration of VSL-3 improved the clinical picture and changed the composition and biochemistry of fecal microbiota. Titer variations of intestinal bacterial groups were evaluated by culture and PCR techniques. A significant increase in lactobacilli, bifidobacteria and Streptococcus thermophilus was observed as a consequence of probiotic treatment, while enterococci, coliforms, Bacteroides and Clostridium perfringens did not change significantly. The strains Bifidobacterium infantis Y1 and Bifidobacterium breve Y8, included in VSL-3, were specifically detected in feces of patients treated with the probiotic by using strain-specific PCR primers. In addition, fecal beta-galactosidase increased and urease activities decreased as a result of changes in the intestinal microbiota induced by VSL-3 administration.

Adult↗
PubMed2004

The effects of di-D-fructofuranose-1,2':2,3'-dianhydride (DFA III) administration on human intestinal microbiota.

Di-D-fructofuranose-1,2':2,3'-dianhydride (DFA III) was shown to enhance Ca absorption in rat and human intestine. The effects of DFA III administration (9 g per day for 4 weeks that corresponded to 3-fold the optimal dosage of DFA III) on human intestinal microbiota were studied using denaturing gradient gel electrophoresis (DGGE). The major groups of human intestinal microbiota reported previously: the Bacteroides, the Clostridium coccoides group (Clostridium cluster XIVa), the Clostridium leptum group (Clostridium cluster IV), and the Bifidobacterium group were detected. The similarity of 30 DGGE profiles based on the V3 region (before and after administration to the 15 subjects) of the 16S rDNA were calculated using Pearson's correlation based on numbers, positions and intensity of bands, and then a dendrogram of DGGE profiles was constructed by the unweighted pair group method using arithmetic average (UPGMA) clustering method. By these analyses, no difference in DGGE profiles after DFA III administration was observed in healthy subjects, while two subjects with chronic constipation showed different profiles, namely on numbers, positions and the intensity of some bands. Their stools were softer and stool frequencies increased and they obtained relief from constipation.

Journal Article↗
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↗
PubMed2002

Influence of Myriophyllum spicatum-derived tannins on gut microbiota of its herbivore Acentria ephemerella.

The submerged living larvae of Acentria ephemerella were fed in the laboratory with either M. spicatum or Potamogeton perfoliatus, two of their host plants. Larvae exhibited a reduced growth when fed M. spicatum, a freshwater angiosperm that contains high concentrations of tannins, secondary metabolites known for their herbivore-deterrent and antimicrobial properties. In this study, we investigated the influence of food-derived tannins on gut microbiota. Bacterial densities in the guts did not differ between the food regimes, ranging from 2.8 to 13.3 x 10(6) cells per gut. Gut bacteria were characterized with cultivation techniques and subsequent identification of the strains by molecular methods. We isolated 17 bacterial strains belonging to all subdivisions, i.e., we identified alpha-, beta-, and gamma-proteobacteria, Cytophyaga/Flavobacteria (CF) and several Gram-positive bacteria. All except one Gram-positive strain were found in the guts of larvae fed with P. perfoliatus. Gram-positive bacteria and bacteria of the CF cluster were more sensitive to polyphenol-containing extracts of M. spicatum in an agar diffusion assay than strains of the alpha- or gamma-proteobacteria subdivision. Our results suggest an influence of food-derived tannins on gut microbiota in A. ephemerella.

Adaptation, Physiological↗
PubMed1999

Proteolysis and utilization of albumin by enrichment cultures of subgingival microbiota.

Subgingival dental plaque consists mainly of microorganisms that derive their energy from amino acid fermentation. Their nutrient requirements are met by the subgingival proteolytic system, which includes proteases from microorganism and inflammatory cells, and substrate proteins from sulcus exudate, including albumin. To determine the selective effect of individual proteins on microbiota, we used albumin as the main substrate for growth. Eight subgingval plaque samples from untreated periodontal pockets of patients with adult periodontitis were inoculated in peptone yeast medium with bovine albumin (9 g/l). After three subculture steps, cell yields of the enrichment cultures at the medium with 0, 1.25, 2.5, 5, 10, and 20 g/l albumin were determined. Proteolytic activity (U/absorbance at 550 nm) of the enrichment cultures and different isolates derived from the cultures was estimated by the degradation of resorufin-labeled casein. It was observed that the yield of the mixed culture was albumin limited, and the proteolytic activities of the cultures in albumin broth were higher than in control (peptone broth). Among the isolates from the enrichment cultures, Peptostreptococcus micros, Prevotella melaninogenica, Prevotella buccae and Prevotella bivia demonstrated proteolysis. The frequent occurrence of Streptococcus gordonii and Streptococcus anginosus in the albumin cultures is explained by their ability to utilize arginine as an energy source for growth. Albumin in the medium was partly degraded by pure cultures but completely consumed in enrichment cultures, indicating synergy of bacterial proteinases. It is concluded that the subgingival microbiota possesses proteolytic activity and may use albumin as a substrate for their growth. Enrichment cultures on albumin may serve as a relatively simple in vitro model to evaluate the effects of proteinase inhibitors.

Bacterial Proteins↗
PubMed2000

Profile of subgingival microbiota in children with mixed dentition.

A diversity of microbial species has been detected in children's oral flora at an early age. To investigate the composition of the subgingival microbiota of different groups of teeth in children with mixed dentition, 40 systemically healthy children, aged 7-8 years, randomly chosen, were examined. Subgingival plaque samples were taken from the mesiobuccal sites of 21, 41, 16 and 36 permanent teeth and 53, 73, 64 and 84 deciduous teeth. The samples were cultured for bacterial isolation anaerobically and in 10% CO2 plus air using selective and nonselective media. Forty-five different microbial species were isolated from both permanent and deciduous teeth. Streptococcus sanguis (79-70%), Streptococcus mitis (66-65%), Prevotella melaninogenica (51-57%), Eikenella corrodens (51-52%), Capnocytophaga gingivalis (46-34%), Capnocytophaga ochracea (45-45%), Actinomyces naeslundii (39-60%) and Prevotella intermedia (42-35%) were among the most frequently detected species in permanent and deciduous teeth respectively. Several suspected periodontal pathogens, such as Porphyromonas gingivalis, Prevotella loescheii, Campylobacter gracilis, Bacteroides forsythus, Campylobacter concisus, Peptostreptococcus micros and Selenomonas sputigena, albeit less frequently detected, were present in the microbiota of these children. The bacterial species Streptococcus constellatus, Peptostreptococcus micros, Pseudoramibacter alactolyticus, E. corrodens and Fusobacterium nucleatum were associated with non-bleeding permanent and deciduous teeth whereas Streptococcus intermedius, C. concisus, P. intermedia and P. loescheii were associated with bleeding.

Actinomyces↗
PubMed2002

Similarity of the oral microbiota of pre-school children with that of their caregivers in a population-based study.

This study evaluated the similarity between the oral microbiota of young children and that of their adult caregivers. Oral samples from children (174 dentate and 18 pre-dentate) aged 6-36 months and their caregivers in Saipan were assayed using a DNA probe assay. Many species including Streptococcus mutans, Streptococcus sobrinus, Actinomyces species, Campylobacter rectus, Fusobacterium nucleatum, Prevotella intermedia, and Porphyromonas gingivalis were detected in dentate and pre-dentate children, whereas Bacteroides forsythus was detected only in dentate children. A higher percentage of children were positive for the detection of an individual species if the caregiver was also positive. There were significant relative risks of species detection between dentate children and their caregivers. By logistic regression, there were significant positive associations between species detection in caregiver and in child, but not between species detection and child age or maternal education level. In conclusion, dental pathogens were detected in young, including pre-dentate, children. The microbial profiles of children were strongly associated with the microbiota of their caregivers.

Actinomyces↗
PubMed2003

Subgingival microbiota of renal transplant recipients.

Renal transplant patients undergoing immunosuppressive therapy may experience periodontal side-effects such as gingival overgrowth. This study evaluated the subgingival microbiota of renal transplant recipients with or without periodontal tissue destruction who may have concurrent gingival enlargement. Subgingival paper point samples taken from the deepest probing sites of 38 subjects (one per patient) were examined using direct microscopy and culture techniques. A complex microflora comprising gram-positive and gram-negative cocci, rods and filaments, fusiforms, curved rods and spirochetes was observed using microscopy. Yeasts were occasionally detected. Significantly higher proportions of gram-positive morphotypes, including gram-positive cocci, were observed in samples from periodontally healthy patients. The predominant cultivable microflora from anaerobic culture comprised several species of facultative and obligate anaerobes. Colonization of the subgingival sites by 'foreign' microbes that are normally dermal, intestinal or vaginal flora was detected in up to 50% of the samples. High mean proportions of lost or unidentified species were also occasionally noted. The results showed that the subgingival biofilm of renal transplant recipients with chronic periodontitis comprised mainly gram-negative rods and spirochetes. Besides the usual predominant cultivable subgingival microbiota associated with periodontitis, the high prevalence of unidentified and 'foreign' microbes indicates the possibility of subgingival microbial alteration in renal transplant patients.

Adult↗
PubMed2000

Differences in the composition of the subgingival microbiota of two periodontitis populations of different geographical origin. A comparison between Spain and The Netherlands.

The purpose of this study was to compare the subgingival microbiota of two geographically distinct patient populations using identical clinical and bacteriological methods. Adult patients with a diagnosis of periodontitis were consecutively selected according to pre-defined clinical criteria. Microbiological samples were taken from the deepest four sites with bleeding. The samples were plated on blood agar plates, for the determination of the total anaerobic counts and identification of specific bacterial pathogens, and on TSBV and McConkey for isolation of Actinobacillus actinomycetemcomitans and enteric rods, respectively. Thirty-one patients in Spain and 30 patients in The Netherlands were selected. Both patient groups showed similar clinical characteristics, both in terms of age, gender and periodontal clinical variables. A. actinomycetemcomitans was significantly more prevalent (23.3% vs. 3.2%) in the Dutch group, while Porphyromonas gingivalis was significantly more prevalent (64.5% vs. 36.7%) in the Spanish group. Bacteroides forsythus and most commensal periodontal pathogens showed similar prevalences, except Peptostreptococcus micros that was significantly more frequent in the Dutch group (96.7% vs. 74.2%). In summary, the subgingival microbiota from the Spanish group was characterised by a high prevalence of P. gingivalis and low of A. actinomycetemcomitans, while the flora from the Dutch group was characterised by a high prevalence of A. actinomycetemcomitans and P. micros.

Aggregatibacter actinomycetemcomitans↗