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PubMed2005

Adhesion of selected Bifidobacterium strains to human intestinal mucus and the role of adhesion in enteropathogen exclusion.

The ability of potential probiotic strains to adhere to the intestinal mucosa and exclude and displace pathogens is of utmost importance for therapeutic manipulation of the enteric microbiota. The ability of seven selected human bifidobacterial strains and five human enteropathogenic strains to adhere to human intestinal mucus was analyzed and compared with that of four strains isolated from chicken intestines. The adhesion of the bifidobacterial strains ranged from 3 to 16% depending on the strain. Bifidobacterium strains of animal origin adhered significantly better than did strains of human origin. Of the pathogenic bacteria, Escherichia coli NCTC 8603 had the highest adhesion value (20%), Salmonella Typhimurium ATCC 29631, Enterobacter sakazakii ATCC 29544, and Clostridium difficile ATCC 9689 had adhesion values ranging from 10 to 15%, and Listeria monocytogenes ATCC 15313 had the lowest adhesive value (3%). The ability of these bifidobacteria to inhibit pathogen adhesion and to displace pathogens previously adhering to mucus was also tested. The inhibition of pathogens adhesion by these bifidobacterial strains was variable and clearly strain dependent. In general, bifidobacterial strains of animal origin were better able to inhibit and displace pathogens than were human strains. Preliminary characterization of bacterial adhesion was accomplished using different pretreatments to explore adhesion mechanisms. The results indicate that different molecules are implicated in the adhesion of bifidobacteria to the human intestinal mucus, constituting a multifactorial process.

Analysis of Variance↗

PubMed2006

Vancomycin-resistant Enterococci may obtain nutritional support by scavenging carbohydrate fragments generated during mucin degradation by the anaerobic microbiota of the colon.

Vancomycin-resistant Enterococcus (VRE) is an important nosocomial pathogen that colonizes the intestinal tract. The substrates that provide nutritional support for VRE in the colon are not known. We tested the hypothesis that enzymatic breakdown of complex polysaccharides and glycoconjugates by other members of the indigenous microbiota could provide a source of nutrients for VRE. Nine vancomycin-resistant E. faecium strains were unable to ferment complex plant polysaccharides or hog gastric or bovine submaxillary mucin; however, each of the strains was able to ferment monosaccharides that are components of mucins and plant polysaccharides. Preincubation of hog gastric mucin with partially purified enzyme mixtures obtained from supernatants of Ruminococcus torques or a human stool specimen resulted in release of monosaccharides that supported growth of VRE. These results suggest that enzymatic breakdown of complex polysaccharides such as mucin by members of the indigenous microbiota may provide a source of nutritional support for VRE.

Bacteroides↗

PubMed2004

The metabolic activity of fecal microbiota from healthy individuals and patients with inflammatory bowel disease.

The hypothesis was studied that intestinal microbial metabolites play a role in the pathogenesis of inflammatory bowel disease. For that purpose, an in vitro model of the colon was inoculated with fresh feces of six healthy individuals and eight inflammatory bowel disease patients. Samples were taken from the model over time to analyze metabolites from both saccharolytic and proteolytic fermentation. Microbiotas from inflammatory bowel disease patients produced significantly more short-chain fatty acids and ammonia than microbiotas from healthy individuals. Furthermore, the branched-chain fatty acid production was 25% higher after inoculation with microbiotas from patients than after inoculation with microbiotas from healthy individuals. Phenolic compounds were produced by all microbiotas, with large interindividual variation. The production of (potentially toxic) metabolites may play a role in the onset or chronicity of inflammatory bowel disease, because they were produced in higher amounts by microbiotas from these patients than by microbiotas from healthy individuals.

Adult↗

PubMed2003

Immunologic regulation of toll-like receptors in gut epithelium.

PURPOSE OF REVIEW: In response to the presence of pathogens in the environment, the innate immune system has evolved to provide a rapid defense against microbes. This response involves the recognition of molecular patterns present in diverse microbes by a series of receptors termed toll-like receptors. The focus of this article is the regulation of toll-like receptor signaling in the intestinal epithelium. The intestinal epithelium is continually exposed to a high concentration of diverse bacteria. In spite of the density of commensal bacteria, the normal intestine is not inflamed. Idiopathic inflammatory bowel disease in humans and animals is characterized by aberrant host-microbial interactions. RECENT FINDINGS: Several studies demonstrate that intestinal epithelial cells are poorly responsive to microbial products. The reason for this hyporesponsiveness is decreased or polarized expression of toll-like receptor molecules. Inflammatory cytokines upregulate expression of toll-like receptors. SUMMARY: The intestinal epithelium has evolved under the pressure of the microbiota to mute a response to commensal bacteria while maintaining the ability to respond to pathogens. In inflammatory bowel disease, the loss of tolerance to the normal flora may be due in part to inappropriate toll-like receptor signaling.

Journal Article↗

PubMed2025

Hatching of whipworm eggs induced by bacterial contact is serine-protease dependent.

Whipworms (Trichuris spp) are ubiquitous parasites of humans and domestic and wild mammals that cause chronic disease, considerably impacting human and animal health. Egg hatching is a critical phase in the whipworm life cycle that marks the initiation of infection, with newly hatched larvae rapidly migrating to and invading host intestinal epithelial cells. Hatching is triggered by the host microbiota; however, the physical and chemical interactions between bacteria and whipworm eggs, as well as the bacterial and larval responses that result in the disintegration of the polar plug and larval eclosion, are not completely understood. Here, we examined hatching in the murine whipworm, Trichuris muris, and investigated the role of specific bacterial and larval structures and molecules in this process. Using scanning and transmission electron microscopy, we characterised the physical interactions of both fimbriated (Escherichia coli, Salmonella typhimurium and Pseudomonas aeruginosa) and non-fimbriated (Staphylococcus aureus) bacteria with the egg polar plugs during the induction/initiation stage, and visualised the effects of structural changes in the polar plugs, leading to larval eclosion. Further, we found that protease inhibitors blocked whipworm hatching induced by both fimbriated and non-fimbriated bacteria in a dose-dependent manner, suggesting the partial involvement of bacterial enzymes in this process. In addition, we identified the minimal egg developmental timing required for whipworm hatching, and transcriptomic analysis of T. muris eggs through embryonation revealed the specific upregulation of serine proteases (S01A family) in fully embryonated eggs containing 'hatch-ready' L1 larvae. Finally, we demonstrated that inhibition of serine proteases with the serine-protease inhibitor Pefabloc ablated T. muris egg hatching induced by bacteria. Collectively, our findings unravel the temporal and physicochemical bacterial-egg interactions leading to whipworm hatching and indicate serine proteases of both bacterial and larval origin mediate these processes.

Animals↗

PubMed1965

Colonization of the mouse intestine with Escherichia coli.

Young albino Swiss mice, of the NCS and NCS-D colonies, proved highly susceptible to the establishment of intestinal infection with an enteropathogenic strain of E. coli administered per os or by stomach tube. The period of highest susceptibility was rather short, extending from the day of birth to approximately 2 weeks of age. Adult NCS and NCS-D mice failed to become experimentally colonized with E. coli, even when large doses were administered per os on 3 consecutive days. The extent of colonization of the various parts of the gastrointestinal tract was related to the size of the infective dose. Many of the young mice died within 2 to 3 days following per os infection with large doses of enteropathogenic E. coli. However, practically all the animals which survived cleared their intestinal infection at approximately the same age. For example, in mice infected with 23 x 10(6) bacteria, colonization of the intestinal tract usually came to an abrupt end when the animals were 24 to 28 days old, irrespective of the age at which they had been infected. There is suggestive evidence that the acquisition of resistance with age, and the ability of adult animals to control the intestinal infection, are related to the development in the gastrointestinal tract of a microbiota which is antagonistic to E. coli.

Aging↗

PubMed1998

The effect of dietary fatty acids on lactic acid bacteria associated with the epithelial mucosa and from faecalia of Arctic charr, Salvelinus alpinus (L.).

Arctic charr, Salvelinus alpinus (L.), held in fresh water, were fed four experimental diets containing different polyunsaturated fatty acids (PUFA). In addition, one group fed a diet containing only coconut oil as sole lipid source served as control. The population of aerobic heterotrophic bacteria associated with the epithelial mucosa and the faecalia was estimated using the dilution plate technique. Generally, the population level of adherent bacteria increased along the digestive tract (stomach, small intestine and large intestine). Adherent Gram-negative and Gram-positive bacteria seemed to be present at equal levels in all parts of the alimentary tract. Lactic acid bacteria dominated among the Gram-positive bacteria, and they were detected in all regions of fish fed the PUFA supplemented diets. The frequency of lactic acid bacteria was highest in the digestive tract of fish fed diets with added 7.0% linolenic acid (18:3 n-3) or 4% of a PUFA mix. A lower frequency of lactic acid bacteria was found in fish fed dietary linoleic acid (18:2 n-6), and they were absent or present in low numbers in fish fed the coconut oil diet. It is suggested that dietary fatty acids affect the attachment sites for the gastrointestinal microbiota, possibly by modifying the fatty acid composition of the intestine wall. Numerical taxonomy procedures showed that the lactic acid bacteria Carnobacterium spp. and a Carnobacterium piscicola-like strain were predominant, with smaller numbers of Lactobacillus plantarum, Streptococcus spp. and Leuconostoc mesenteroides present. Seven strains of Carnobacterium spp. were further identified on the basis of 16S rDNA sequence analysis, and all these strains were identified as Carnobacterium piscicola.

Animal Feed↗

PubMed1992

2,4,5-trichlorophenoxyacetic acid influence on 2,6-dinitrotoluene-induced urine genotoxicity in Fischer 344 rats: effect on gastrointestinal microflora and enzyme activity.

2,4,5-Trichlorophenoxyacetic acid (2,4,5-T) and 2,6-dinitrotoluene (2,6-DNT) are hazardous chemicals that have potential harmful effects. 2,6-DNT is recognized as a hepatotoxicant while 2,4,5-T, a component of Agent Orange, is also suspect. 2,6-DNT requires both oxidative and reductive metabolism to elicit genotoxic effects. To determine what effect 2,4,5-T had on 2,6-DNT metabolism, intestinal enzymes, microbial populations, and urine mutagenicity were examined during 2,4,5-T treatment. Weanling Fischer 344 male rats were treated daily with 54.4 mg/kg 2,4,5-T by gavage for 4 weeks. One, two, and four weeks after the initial 2,4,5-T dose, rats were administered (po) 2,6-DNT (75 mg/kg) and urine was collected for 24 hr in metabolism cages. Azo reductase, nitroreductase, beta-glucuronidase, dechlorinase, and dehydrochlorinase activities were examined concurrently. Treatment of rats for 1 week reduced the transformation of 2,6-DNT to mutagenic urinary metabolites. This was accompanied by a decrease in the fecal anaerobic microorganisms. The elimination of Lactobacillus fermentum from the small intestine and cecum of treated animals accompanied a significant increase in oxygen-tolerant lactobacilli and other unidentified aerobic microorganisms. However, there were no significant alterations in the intestinal enzyme activities examined. By 2 weeks of 2,4,5-T treatment, microbiota and urine genotoxicity returned to the levels observed in control animals. This trend continued for the duration of the experiment. After 2 weeks, while cecal nitroreductase and azo reductase activities increased, small intestinal beta-glucuronidase activity decreased. By 4 weeks, treated and untreated animal intestinal enzyme activities were indistinguishable.(ABSTRACT TRUNCATED AT 250 WORDS)

2,4,5-Trichlorophenoxyacetic Acid↗

PubMed2001

Antagonism against Vibrio cholerae by diffusible substances produced by bacterial components of the human faecal microbiota.

Cholera vibrios sometimes survive, probably in low-level silent populations, in the small intestine of chronic carriers or pass through the gastrointestinal tract of a few individuals without causing diarrhoea or colonisation. To understand these situations, the present study used plate cultures (ex-vivo test) to investigate the frequency of appearance of an inhibitory halo against Vibrio cholerae produced by faecal specimens from 92 healthy volunteers (40 females, 52 males) aged 4-61 years. The frequency of inhibitory halo was 20.6% in the whole group. An apparently higher percentage (27.3%) was observed in the age range 20-40 years when compared with the range 4-19 years (10.7%), but not the range 41-61 years (20.0%). Frequency was significantly higher in males (30.8%) than females (7.5%). The dominant microbiota of a volunteer whose faeces produced an inhibitory halo was isolated by plate culture of decimal dilutions in an anaerobic chamber. Potential isolates of 26 apparently different morphologies were associated with germ-free NIH mice. One week later, the inhibitory test showed an antagonistic halo around the faeces from the associated animals, but not from the axenic mice. Of the 26 bacteria isolated, two (Lactobacillus sp. and Peptostreptococcus sp.) produced a compound antagonistic against V. cholerae in an in-vitro assay. When bi-associated with germ-free mice those strains eliminated the vibrio from the intestinal ecosystem in c. 5 days.

Adolescent↗

PubMed1995

Intestinal B-cell isotype response in relation to local bacterial load: evidence for immunoglobulin A subclass adaptation.

BACKGROUND & AIMS: In experimental animals, the indigenous microbiota modulates mucosal immunity. In humans, such direct evidence is scarce. The aim of this study was to examine the effect of intestinal bacteria on the local immunoglobulin (Ig) response. METHODS: The numbers of IgA-, IgM-, and IgG-producing immunocytes per defined mucosal length unit were determined, and the local IgA subclass response was studied using immunohistochemistry in jejunal segments from adults with bacterial overgrowth and in sterile ileal urinary conduits from children. RESULTS: The ileal bladder mucosa showed atrophy, but the number of immunocytes only tended to be decreased. The jejunal segments with bacterial overgrowth showed minor histological changes; the numbers of IgA and IgG immunocytes were fairly normal, whereas the number of IgM immunocytes was significantly reduced (P < 0.05) (12 cells/U) compared with control mucosa (24 cells/U). The number of IgA2 immunocytes was significantly decreased (P < 0.01) in ileal conduits (7 cells/U or 30% of total IgA) but increased (P < 0.05) in jejunal segments with bacterial overgrowth (42 cells/U or 43% of total IgA) compared with normal ileum (15 cells/U or 40% of total IgA) and jejunum (24 cells/U or 23% of total IgA). CONCLUSIONS: An association exists between bacterial load and IgA subclass production. An increase in IgA2 may enhance mucosal protection and probably reflects immunomodulation caused by lipopolysaccharides.

Adolescent↗

PubMed2006

Effects of bovine alpha-lactalbumin and casein glycomacropeptide-enriched infant formulae on faecal microbiota in healthy term infants.

OBJECTIVE: Certain milk factors may promote the growth of a host-friendly gastrointestinal microbiota, for example, one that is predominated by bifidobacteria, a perceived health-promoting genus. This may explain why breast-fed infants experience fewer intestinal infections than their formula-fed counterparts who are believed to have a more diverse microbiota, which is similar to that of adults. The effects of formulas supplemented with 2 such ingredients from bovine milk, alpha-lactalbumin (alpha-lac) and casein glycomacropeptide (GMP), on gut flora were investigated in this study. PATIENTS AND METHODS: Six-week-old (4-8 wk), healthy term infants were randomised to a standard infant formula or 1 of 2 test formulae enriched in alpha-lac with higher or lower GMP until 6 months. Faecal bacteriology was determined by the culture-independent procedure fluorescence in situ hybridisation. RESULTS: There was a large fluctuation of bacterial counts within groups with no statistically significant differences between groups. Although all groups showed a predominance of bifidobacteria, breast-fed infants had a small temporary increase in counts. Other bacterial levels varied in formula-fed groups, which overall showed an adult-like faecal microflora. CONCLUSIONS: It can be speculated that a prebiotic effect for alpha-lac and GMP is achieved only with low starting populations of beneficial microbiota (eg, infants not initially breast-fed.

Animals↗

PubMed2004

Getting a grip on things: how do communities of bacterial symbionts become established in our intestine?

The gut contains our largest collection of resident microorganisms. One obvious question is how microbial communities establish and maintain themselves within a perfused intestine. The answers, which may come in part from observations made by environmental engineers and glycobiologists, have important implications for immunologists who wish to understand how indigenous microbial communities are accommodated. Here we propose that the mucus gel layer overlying the intestinal epithelium is a key contributor to the structural and functional stability of this microbiota and its tolerance by the host.

Animals↗

PubMed1997

Modification of the intestinal microflora using probiotics and prebiotics.

Probiotics and prebiotics modulate the composition of the human gut microbiota. The beneficial effects may result from suppression of harmful microorganisms or stimulation of organisms which contribute in a positive way to the nutrition and health of the host. Both types of supplement represent an attempt to reconstitute the gut flora to its normal composition which has been adversely affected by dietary and environmental stresses.

Animals↗

PubMed2001

Metabolism, microflora effects, and genotoxicity in haloacetic acid-treated cultures of rat cecal microbiota.

Haloacetic acids are by-products of drinking water disinfection. Several compounds in this class are genotoxic and have been identified as rodent hepatocarcinogens. Enzymes produced by the normal intestinal bacteria can transform some promutagens and procarcinogens to their biologically active forms. The present study was designed to investigate the influence of the cecal microbiota on the mutagenicity of haloacetic acids, and to look at changes in the microbiota populations and enzyme activities associated with exposure to haloacetic acids. PYG medium containing 1 mg/ml of monochloroacetic (MCA), monobromoacetic (MBA), dichloroacetic (DCA), dibromoacetic (DBA), trichloroacetic (TCA), tribromoacetic (TBA), or bromochloroacetic (BCA) acid was inoculated with rat cecal homogenate and incubated anaerobically at 37 degrees C. Growth curves were performed with enumeration of the microflora populations on selective media. Mutagenicity in a Salmonella microsuspension bioassay was determined after incubation for various lengths of time, with or without the cecal microbiota. At 15 h of incubation, enzyme assays determined the activities for beta-glucuronidase, beta-galactosidase, beta-glucosidase, azoreductase, nitroreductase, dechlorinase, and dehydrochlorinase. The haloacetic acids, with the exception of BCA, were toxic to the cecal microbiota, and especially to the enterococci. DBA, TBA, and BCA were mutagenic in the microsuspension assay, but the presence of the intestinal flora did not significantly alter the mutagenicity. BCA increased the activities of several enzymes, and therefore has the potential to affect the biotransformation of co-exposed compounds.

Acetates↗

PubMed1995

Dietary modulation of the human colonic microbiota: introducing the concept of prebiotics.

Because the human gut microbiota can play a major role in host health, there is currently some interest in the manipulation of the composition of the gut flora towards a potentially more remedial community. Attempts have been made to increase bacterial groups such as Bifidobacterium and Lactobacillus that are perceived as exerting health-promoting properties. Probiotics, defined as microbial food supplements that beneficially affect the host by improving its intestinal microbial balance, have been used to change the composition of colonic microbiota. However, such changes may be transient, and the implantation of exogenous bacteria therefore becomes limited. In contrast, prebiotics are nondigestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacterial species already resident in the colon, and thus attempt to improve host health. Intake of prebiotics can significantly modulate the colonic microbiota by increasing the number of specific bacteria and thus changing the composition of the microbiota. Nondigestible oligosaccharides in general, and fructooligosaccharides in particular, are prebiotics. They have been shown to stimulate the growth of endogenous bifidobacteria, which, after a short feeding period, become predominant in human feces. Moreover, these prebiotics modulate lipid metabolism, most likely via fermentation products. By combining the rationale of pro- and prebiotics, the concept of synbiotics is proposed to characterize some colonic foods with interesting nutritional properties that make these compounds candidates for classification as health-enhancing functional food ingredients.

Bacteria↗

PubMed2003

Potential rates of fermentation in digesta from the gastrointestinal tract of pigs: effect of feeding fermented liquid feed.

Microbial catabolic capacity in digesta from the gastrointestinal tract of pigs fed either dry feed or fermented liquid feed (FLF) was determined with the PhenePlate multisubstrate system. The in vitro technique was modified to analyze the kinetics of substrate catabolism mediated by the standing stock of enzymes (potential rates of fermentation), allowing a quantitative evaluation of the dietary effect on the catabolic capacity of the microbiota. In total, the potential rates of fermentation were significantly reduced in digesta from the large intestine (cecum, P < 0.1; colon, P < 0.01; and rectum, P < 0.0001) of pigs fed FLF compared to pigs fed dry feed. No effect of diet was observed in the stomach (P = 0.71) or the distal part of the small intestine (P = 0.97). The highest rates of fermentation and the most significant effect of diet were observed for readily fermentable carbohydrates like maltose, sucrose, and lactose. Feeding FLF to pigs also led to a reduction in the large intestine of the total counts of anaerobic bacteria in general and lactic acid bacteria specifically, as well as of microbial activity, as determined by the concentration of ATP and short-chain fatty acids. The low-molecular-weight carbohydrates were fermented mainly to lactic acid in the FLF before being fed to the animals. This may have limited microbial nutrient availability in the digesta reaching the large intestine of pigs fed FLF and may have caused the observed reduction in activity and density of the cecal and colonic microbial population. On the other hand, feeding FLF to pigs reduced the viable counts of coliform bacteria (indicator of Escherichia coli and Salmonella spp.) most profoundly in the stomach and the distal part of the small intestine, probably due to the bactericidal effect of lactic acid and low pH. The results presented clearly demonstrate that feeding FLF to pigs had a great impact on the indigenous microbiota, as reflected in bacterial numbers, short-chain fatty acid concentration, and substrate utilization. However, completely different mechanisms may be involved in the proximal and the distal parts of the gastrointestinal tract. The present study illustrates the utility of the PhenePlate system for quantifying the catabolic capacity of the indigenous gastrointestinal tract microbiota.

Animal Feed↗

PubMed2002

Developmental regulation of intestinal angiogenesis by indigenous microbes via Paneth cells.

The adult mouse intestine contains an intricate vascular network. The factors that control development of this network are poorly understood. Quantitative three-dimensional imaging studies revealed that a plexus of branched interconnected vessels developed in small intestinal villi during the period of postnatal development that coincides with assembly of a complex society of indigenous gut microorganisms (microbiota). To investigate the impact of this environmental transition on vascular development, we compared the capillary networks of germ-free mice with those of ex-germ-free animals colonized during or after completion of postnatal gut development. Adult germ-free mice had arrested capillary network formation. The developmental program can be restarted and completed within 10 days after colonization with a complete microbiota harvested from conventionally raised mice, or with Bacteroides thetaiotaomicron, a prominent inhabitant of the normal mouse/human gut. Paneth cells in the intestinal epithelium secrete antibacterial peptides that affect luminal microbial ecology. Comparisons of germ-free and B. thetaiotaomicron-colonized transgenic mice lacking Paneth cells established that microbial regulation of angiogenesis depends on this lineage. These findings reveal a previously unappreciated mechanism of postnatal animal development, where microbes colonizing a mucosal surface are assigned responsibility for regulating elaboration of the underlying microvasculature by signaling through a bacteria-sensing epithelial cell.

Animals↗

PubMed2004

Effects of two probiotic Lactobacillus strains on jejunal and cecal microbiota of broiler chicken under acute heat stress condition as revealed by molecular analysis of 16S rRNA genes.

We examined the effects of probiotic Lactobacillus strains of Lactobacillus agilis JCM 1048 and Lactobacillus salivarius subsp. salicinius JCM 1230 on jejunal and cecal microbiota of broiler chicken under heat stress condition using terminal restriction fragment length polymorphism (T-RFLP) analysis. The jejunal bacterial community was limited to a few bacterial groups, mostly Lactobacillus spp. A relatively abundant and higher prevalence of Lactobacillus spp. were observed in the jejunal and cecal microbiota of the probiotic chickens compared with those of the control chickens under heat stress condition. In general, the probiotic strains did not significantly affect the abundance of L. agilis and L. salivarius in chicken intestine but clearly contributed to increasing their prevalence in the probiotic chickens. The probiotic Lactobacillus strains enriched the diversity of Lactobacillus flora in chicken jejunum and cecum by increasing the abundance and prevalence of Lactobacillus spp. inhabiting the intestine. The richness of Lactobacillus species tended to be similar among the jejunal and cecal microbiota. The bacterial community of cecum was complex and age-dependent. The major components of the cecal microbiota were clostridia and lactobacilli. The Clostridium subcluster XIVa was the most predominant group in chicken cecum. Probiotic Lactobacillus strains restored the microbial balance and maintained the natural stability of indigenous bacterial microbiota following heat stress-induced changes.

Age Factors↗