Beta Glucuronidase

The formation of glucuronides in the liver is an important mechanism for detoxifying and enhancing excretion of a large number of orally ingested nutrients and their end products, other dietary compounds, and drugs, as well as endogenously synthesized compounds, such as estrogens. In humans many of these glucuronides depending on the structure of the aglycone, are excreted in the bile, and subsequently enter the duodenum. The glucuronides are then subject to bacterial deconjugation primarily in...

Activation of the Immune System

Innate immunity plays a very important role in the activation of the immune system and the ability to develop specific acquired immune responses. Through their Ag-presenting activity and the synthesis of numerous pro-inflammatory chemokines and cytokines (IL-8, IL-1, IL-6, TNF-a, and IL-12), macrophages, and DCs play a key role in the regulation of immune responses. They are the gatekeepers of the host, generating innate resistance to pathogens, and specific immune responses by the stimulation...

Fingerprinting Reveals Characteristics Of The Microbiota

PCR-Denaturing Gradient Gel Electrophoresis The most commonly applied fingerprinting methods used to study the GI-tract microbiota are denaturing and temperature gradient gel electrophoresis (DGGE and TGGE, respectively) of PCR-amplified genes coding for 16S rRNA (Fig. 1) (12,23). Other techniques such as terminal restriction fragment length polymorphism (T-RFLP) and single strand conformation polymorphism (SSCP) analysis are being applied but less frequently (26,29). The common principle of...

Penicillins

The effect of penicillins on the gastrointestinal microbiota is summarized in Table 1. Phenoxymethylpenicillin Phenoxymethylpenicillin has been shown to induce minor variations in numbers of aerobic and anaerobic gastrointestinal microorganisms in healthy adults (5,6) and in infants treated for upper or lower respiratory tract infections or otitis media (7). Penicillin that reaches the gastrointestinal tract is destroyed by beta-lactamase produced by the microorganisms. Despite the low...

Reflection of Effects on Allergen Uptake Processing and Presentation

The original hygiene hypothesis implicated pathogens in an allergy-preventing role. However, their role may be two-sided (90). Whereas the host immune system may become tolerant towards commensal microbes, this should and will not happen with pathogens (91,92). Therefore, pathogens may have a greater potential to stimulate the neonatal immunity away from the allergic type responsiveness than the commensal microbes towards which tolerance has been formed (90). Conversely, potential pathogens may...

Microbial Degradation of Mucin

Mucin in the GI tract is produced by goblet cells in the mucosa and glandular mucous cells in the submucosa. Mucin consists of a peptide core with oligosaccharide side chains O-glycosidically bound, and it has several important physiological and patho-physiological roles. It acts as lubricant, as a barrier and stabilizer for the intestinal microclimate as well as a source of energy for the microbiota. There is growing evidence that the mucin pattern may be a relevant issue to take into account...

Brief Review Of Immune Responses Innate Immunity

Cells responsible for the innate immunity provide the first line of host defense monocytes macrophages, dendritic cells (DC), natural killer cells (NK), and neutrophils. These are the body's sentinels, able to detect danger and signal it to other cells, by the synthesis of molecules, such as NO (nitric oxide) which displays antibacterial activity, cytokines, and chemokines, which are small peptides acting by means of specific receptors expressed at the surface of targeted cells. Some of them...

Advantages over Antibiotics

Eliminating pathogenic groups with antibiotics is an obvious approach to beneficially modifying the intestinal microbiota. However, perturbation of indigenous microbial ecosystems caused by the collateral damage to desirable populations can lead to potentially serious side effects. These include antibiotic-associated diarrhea and pseudomembranous colitis involving overgrowth of Clostridium difficile as well as oral or vaginal candidiasis (173-175). Prebiotics and probiotics can ameliorate the...

Reflection of Effects on Th1 Th2 and Treg Differentiation

The effects of intestinal bacteria on cytokine production, epithelia-damaging action or proinflammatory action may have a major influence on naive T-cell differentiation to Th1, Th2 or Treg cells (Fig. 2). A study in mice with compromised Toll-mediated signaling capacity indicated that antigen specific Th1 responses to food allergens are dependent on simultaneously induced Toll-mediated activities, whilst similar dependency was not observed in Th2 responses. Re-exposing the mice to the allergen...

Allergyassociated Compositional Characteristics Of Infant Gut Microbiota

The predominant site for host-microbe interaction is in the gut. Thus, its compositional development has been suggested to be the key determinant in whether or not the atopic genotype will be fully expressed and thereby affect the development of allergic diseases. The determination of characteristics in compositional development of intestinal microbiota in association with the expression of allergies may provide a starting point for elucidating which microbial components, if any, may have...

Modifying The Intestinal Microbiota Pre And Probiotics

First documented studies of dietary manipulation of canine and feline intestinal microbiota date back to the beginning of the twentieth century (71). Today, there is growing interest in modifying their gut microbiota towards what is considered a healthy composition, i.e., increase in LAB and bifidobacteria, and decrease in potential pathogenic bacteria (72). Many commercial pet foods now contain prebiotics (e.g., fructo-oligosaccharides, FOS). In addition, probiotics are also marketed for dogs...

Info

Abbreviations BT, breath test H2, hydrogen. Source From Refs. 42, 51, 78, 80, 84, 101-105. Abbreviations BT, breath test H2, hydrogen. Source From Refs. 42, 51, 78, 80, 84, 101-105. To diagnose bacterial overgrowth, various breath tests may be used including the 14C-glycocholate, 14C-D-xylose, lactulose-H2, and glucose-H2 tests. The rationale for the breath test is the production of volatile metabolites i.e., carbon dioxide (CO2), hydrogen (H2) or methane (CH4), by intraluminal bacteria from...

Perorally Administered Cephalosporins

Studies on the effects of perorally administered cephalosporins are summarized in Table 3. Alterations in the intestinal microbiota during administration of cefaclor have been studied in patients (19) and in healthy volunteers (51,52). In the microbiota of patients there were reduced numbers of both aerobic and anaerobic Gram-positive cocci. Enterococci, enterobacteria and Bacteroides species increased and there were also increased numbers of Candida albicans. In healthy subjects only minor...

Influence of Age Related Decline in Immune Function and Influence on Intestinal Bifidobacteria Microbiota

Immunosenescence is defined as the state of deregulated immune function that contributes to the increased susceptibility of the elderly to infection and, possibly, to autoimmune diseases and cancer (49,50). When immunosenescence appears, the functional capacity of the immune system of the host gradually declines with age. The most dramatic changes in immune function with age occur within the T cells compartment, the arm of the immune system that protects against pathogens and tumors (51-54)....

Investigations At The Subspecies Level

One aspect of gut microbiology that is not amenable to current probing or PCR-based methodologies is subspecies differentiation (i.e., investigations of the microbial complexity and dynamics below the phylogenetic level of species). A number of studies have, however, demonstrated the importance of such research (48,51,52). One study monitored the composition of the bifidobacterial and lactobacilli populations of two healthy humans over a 12-month period (52). Overall, the bifidobacterial levels...

Development Of Gi Tract Normal Microbiota In Humans

The fetus in utero is sterile until birth. Colonization of the human body with a heterogenous collection of microorganisms from the birth canal begins at delivery. The Lactobacillus species constitute the major population of the vaginal microbiota and thus provide the initial inoculum to the infant during birth. In the case of caesarean section or premature infants, most microbes that are transferred to the newborn can be traced from the environment, i.e., from other infants via the air,...

In Situ Profiling Of Transcription In The Gi Tract

As soon as sequence data is available for a few genes in a bacterium of interest, one could think of several sophisticated tools that allow investigation of the in situ expression levels of specific genes. One example of such an approach is the implementation of quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) in the gram-negative bacterium Helicobacter pylori (66). This study describes the assessment of gene expression in this pathogen within the mouse and human gastric...

Mechanisms Of The Bifidogenic Effect

The mechanism(s) by which prebiotics promote the relatively specific proliferation of bifidobacteria remain speculative. It is probably due to the efficient utilization of these carbohydrates as carbon and energy sources by bifidobacteria relative to other intestinal bacteria, and their tolerance to the SCFA and acidification of the microenvironment resulting from fermentation. Additionally, many bifidobacteria adhere to large granular substrates such as resistant starch and these may provide a...

Glucose Hydrogen Breath Test

Glucose hydrogen breath tests can also be used to detect SBBO. Glucose is completely absorbed before reaching the colon even in patients with previous gastric surgery, who have faster than normal transit. Patients receive a solution containing 50-80 g of glucose dissolved in 250 ml water after fasting for 12 hours. Breath hydrogen concentrations are analyzed with an H2 monitor after direct expiration through a Y-piece that prevents air from mixing with the exhaled hydrogen (84). Hydrogen...

Gut Bacterial Metabolism and CRC Risk

The enormous numbers and diversity of the human gut microbiota is reflected in a large and varied metabolic capacity, particularly in relation to xenobiotic biotransformation, carcinogen synthesis and activation. The metabolic activities of the gut microbiota can have wide-ranging implications for the health of the host (42). To date the vast majority of mechanisms whereby bacteria are involved in carcinogenesis involve toxic or protective products of bacterial metabolism. Such metabolic...

Bacterial Cholesterol Metabolism

The intestinal tract has a major impact on cholesterol metabolism (34-36). A major source of intestinal cholesterol comes from the de novo synthesis of the sterol compound. Cholesterol also can enter the intestine from dietary sources. It has been estimated that 34-57 of dietary cholesterol is absorbed from the intestine (37). In humans cholesterol synthesized by the intestinal cells is introduced into the lumen by exfoliation of these cells. An additional source of intestinal cholesterol is...

Experimental Animal Models Gnotobiotic Mice

In experimental studies, the role of the digestive microbiota is determined by comparison between GF and conventional (CV) animals, or GF mice colonized with a human fecal microbiota, the humanized-mice. Several results show that the human fecal microbiota reproduces the same immunostimulatory effects as those produced by the mouse intestinal microbiota (60,61), and consequently, this mouse model is a very interesting tool for human studies. The first step is the demonstration of the effect of...

Manipulation of the Gastrointestinal Microbiota by Application of Probiotic Microorganisms

Administration of preparations based on autochthonous microorganisms is a very effective method of affecting the microbiota of the gastrointestinal tract in farm animals. In this way development of the microbiota of the young at an early age and around weaning can be influenced. Development of the rumen microbiota in calves and lambs can be supported by microbial preparations mainly at the start of dry feeding. Effective use of microbial preparations in the young depends also on the level of...

Clostridia

Clostridium perfringens is an anaerobic, spore-forming bacillus associated with acute and chronic diarrhea in dogs and cats. However, the role of C. perfringens as an intestinal pathogen is questionable, as it commonly harbors in the intestinal tract of healthy dogs, too (23,32). C. perfringens produces toxins, which are classified in five toxigenic types (A-E). C. perfringens enterotoxin (CPE) is the best characterized virulence factor and coregulated with sporulation. All C. perfringens types...

Conclusion

It has been well established that allergic sensitization and the development of allergic disease are associated, at least in some infants, with characteristic developmental patterns in fecal microbiota composition that are atypical to healthy infants. With relative consistency these characteristics include low numbers of bifidobacteria and anaerobes in total and high numbers of clostridia, S. aureus and certain coliforms such as Klebsiellae. Data on lactobacilli, Bacteroides and E. coli are...

Surgically Modified Animals

Surgical modification of the GIT gives new opportunities for the study of the GI microbiota. Using surgical procedures, specific parts of the GIT can be removed in order to make modifications to basic physiology. Surgery can also provide the opportunity, by means of cannulation of the GIT, to give repeated post-surgical access to specific sites of the tract. The human GIT lacks some of the areas that may be found in the rodent and porcine GIT, such as the areas of non-secreting epithelium that...

Helicobacters

Helicobacter spp. are Gram-negative, microaerophilic curved or spiral-shaped motile bacteria. Many gastric Helicobacter-like organisms (GHLO) are frequently found in cats and dogs. Virtually all dogs can be expected to harbor gastric GHLO (60,61), although most of the dogs are asymptomatic. Additionally, the clinical signs in dogs suffering from gastritis may persist despite the eradication of helicobacters. Therefore the role of GHLO as an etiological factor in canine gastritis is currently...

Specific Microorganisms in Inflammatory Bowel Disease

Despite the importance of bacteria in the pathogenesis of colitis and CD, no specific microorganism has been implicated in causing the intestinal inflammation. The roles of Mycobacterium paratuberculosis, measles virus, Listeria monocytogenes and adherent E. coli in the pathogenesis have been examined. Strains of adherent-invasive E. coli have been isolated in the mucosa of patients with CD (48). M. paratuberculosis has been cultured from the intestine of patients with CD and detected by...

The Prebiotic Strategy To Modifying The Intestinal Microbiota

For a variety of reasons, the two bacterial genera most often advocated as beneficial organisms with which to augment the intestinal microbiota are lactobacilli and bifidobacteria, both of which are common members of the human intestinal microbiota (11,12). These bacteria are numerically common, non-pathogenic, non-putrefactive, non-toxigenic, saccharolytic organisms that appear from available knowledge to provide little opportunity for deleterious activity in the intestinal tract. As such,...

Blurring the Distinctions Between Prebiotics Dietary Fibers and Other Fermentable Dietary Carbohydrates in the Colon

The greatest volume of research and evidence for prebiotic effects has been accrued for fructo-oligosaccharides and inulin, but there is accumulating evidence of prebiotic actions by a number of non-digestible carbohydrates. Lactulose and galacto-oligosaccharides have strong claims to be classified as prebiotics, while there is promising evidence for prebiotic activity by isomalto-, xylo-, and soybean-oligosaccharides. There is growing interest in the impact of dietary fibers on the composition...

Other Steroid Hormone Bacterial Conversions

Studies have shown that fecal organisms can modify corticosteroids. The corticosteroids undergo reduction in ring A, and undergo side-chain dehydroxylation separately or sequentially with the reduction (48). Cortisol is converted to 21 -deoxycortisol, tetrahydrocortisol, and tetrahyro-21-deoxycortisol (48). Corticosterone is metabolized to tetrahydrocorticosterone, 21-deoxycorticosterone, and 3-alpha-hydroxy or 3-beta-hydroxy epimers of tetrahydro-21-deoxycorticosterone (48). The intestinal...

Interpreting The Gut Microbiota Characteristics

The reason for the compositional differences in the average microbiota of allergic and healthy infants is not yet known. Undisputable conclusions regarding causal relationship cannot be drawn based on mere characterization of microbial composition relative to clinical sings and symptoms. In a few studies, characteristics of the fecal microbiota have been shown to precede the beginning of the expression of atopy, implying that these differences are not necessarily secondary to the disease....

The Importance Of The Enteric Microbiota In Inflammatory Bowel Disease

Considerable evidence implicates the enteric microbiota in the pathogenesis of inflammatory bowel disease (Table 1) (7,8,30,31). Firstly, mucosal inflammation occurs in areas of the gut with highest bacterial numbers. Secondly, surgical diversion of the fecal stream has been associated with clinical improvement in the distal bowel, but relapse is predictable following surgical restoration. Thirdly, putative therapeutic efficacy is seen with the use of antibiotics in colonic disease. Fourthly,...

Disease Causing Microbiota

Yersinia enterocolitica, Salmonella, Shigella, Campylobacter, Clostridium difficile, enterohemorragic Escherichia coli (EHEC), and enteropathogenic Escherichia coli (EPEC) are the most common pathogenic bacteria in the colon that cause diarrhea. Diarrhea can also occur after oral antibiotic treatment. Poorly absorbed antibiotics change the normal composition of the microbiota in the colon (93). Suppression of the normal microbiota may lead to reduced colonization resistance with subsequent...

Common Trends and Contradictions

The microbial characteristics of infants presented above are summarized in Figure 1. Although some variability exists depending upon the study, there are relatively clear trends evident. The most consistent trends associated with allergy are low numbers of bifidobacteria and high numbers of S. aureus and certain species of coliforms and clostridia. It should be pointed out that there are several aspects of these studies that complicate their interpretation. A fundamental downfall is the...

Effects on Human Health

A growing understanding of the intestinal microbiota and its contribution to health and disease has enabled rational hypotheses to be developed for prebiotic interventions targeted to specific human populations. Testing of these hypotheses is still mostly centered at the animal model or pilot human trial stage. Prebiotic oligosaccharides are already used in some infant formulas and efforts to replicate the activities of HMOs are likely to continue. Although the effects of prebiotics overlap...

Activation of the Intestinal Immune System

It has been shown that the presence of intestinal microbiota plays an important role in the development and activation of IIS even if many effects are still ignored. Its role may be of particular importance in the neonatal period and could determine many of the outcomes in later life. As newborns, GF animals exhibit an underdeveloped IIS, which can be normalized by bacterial colonization of the intestine with the fecal microbiota from a CV animal or human, within 3 weeks. In GF mice, PPs are...

Brief Review Of The Intestinal Microbiota

From birth to death, the gut is colonized by a diverse, complex, and dynamic bacterial ecosystem that constitutes the intestinal microbiota. In newborns, it develops sequentially according to the maturation of intestinal mucosa and dietary diversification. In healthy conditions, the human baby's intestine is sterile at birth but, within 48 hours, 108 to 109 bacteria can be found in 1 g of feces (9-11). The bacteria colonizing the baby's intestine come from the environment, where maternal...

Parenterally Administered Cephalosporins

The spectra of cephalosporins are broader than that of penicillins. Several cephalosporins are excreted biliary and a strong ecological impact can be expected. Enterococci are intrinsically resistant to cephalosporins and their numbers usually increase during administration. The impact of parenterally administered cephalosporins on the gastrointestinal normal microbiota is summarized in Table 2. The impact of intravenously administered cefazolin on the gastrointestinal microbiota has been...

Reflection of Allergic Symptoms

The possibility that allergic symptoms either affect, or are affected by, the microbiota is supported by an observation that alleviation in atopic eczema and allergic inflammation following oral administration of bifidobacteria was accompanied by modified dynamics in the microbiota (i.e., restriction in the growth of E. coli and Bacteroides) (18). Also, earlier findings attest to this possibility implicating direct correlation between numbers of Enterobacteriaceae family bacteria and severity...

Reflection of Atopic Genotype

Incomplete knowledge of the genetic characteristics of allergic diseases restricts the full understanding of their possible influence on the development of gut microbiota (58). Theoretically, microbial colonization could be directly affected for example if the atopic genotype was associated with receptor expression on epithelial cells or production of intestinal mucus. There is some indication that the atopic genotype is associated with Table 1 Possible Causes for Microbial Compositional...

Reflection of Environmental Factors

Amongst the best examples of factors which have been clearly shown to influence the development of the gut microbiota and have also been implicated in allergic diseases include the mode of delivery and breast-feeding (116-123). Indeed, it is plausible that the characteristics of fecal microbiota associated with atopic eczema and allergic sensitization may partly reflect dietary factors. It is well known that changes in diet may dramatically affect the microbial composition of the gut. Then...

Studies by Molecular Methods

Results obtained by molecular-based culture-independent techniques are largely supportive of the findings presented above. In another prospective follow-up, the fecal microbiota in Finnish neonates was studied prior to the expression of atopy as detected by a positive skin prick test at year one (n 12). The microbiota of these sensitized children tended to contain lower numbers of bifidobacteria and significantly higher numbers of Clostridium histolyticum than those in samples from infants with...

Fecal Enzyme Activity

One of the detrimental effects the human intestinal microbiota may have on host health is the production of tumor promoters, mutagens, and carcinogens from undigested dietary substrates and endogenous residues. Bacterial enzymes involved in the formation of such substances are b-glucoronidase, azoreductase, nitroreductase, and nitrate reductase (108) see also the chapters by Rafter and Rowland, and Goldin. A reduction in the activity of these enzymes can be expected to lead to a reduced...

The Intestinal Immune System

The IIS is a particular immune system anatomically and functionally distinct from that present at the peripheral level (30-32). It is in contact with an enormous quantity of Ags, food proteins and intestinal bacteria, and does not mount an inflammatory response against them. At the same time, it has to protect against enteric pathogens and toxins. The IIS is mainly located in the small intestine and colon with differences in the anatomical patterning and physiological functions. It is important...

Large Intestine Microbiota And Sampling Techniques Normal Microbiota

The large intestine including the cecum, colon, and the rectum harbors over 500 species of bacteria, mainly obligate anaerobes (99.9 ) with 1011-1012CFU g (2,10). Microorganisms isolated from large intestine and fecal samples are listed in Table 4. Bacteroides, Bifidobacteria, Eubacteria, Clostridia, and Enterobacteriaceae can predominantly be found in the colon. Novel molecular methods are aiding better understanding of the microbiota, which is challenging to culture due to the anaerobic...

The Role of Microbiota on GI Health

The mammalian microbiota has several important functions. It aids in nutrition by degrading complex nutrients and by synthesizing vitamins. It protects against infectious disease, by either preventing invading pathogenic bacteria from establishing in the GIT, or by conditioning of the mucosal immune system. The microbiota may also influence the development of cancer, by modulation of carcinogens, pre-carcinogens or by activation of immunological responses. Many factors influence the progression...

Quinolones

The ecological impact of quinolone administration on the fecal microbiota is described in Table 7. The ecological consequences of ciprofloxacin have been evaluated in patients in connection with colorectal surgery (92), in patients with acute leukaemia in remission (96), in prevention of bacterial infections in cirrhosis (101,102) and in treatment of travelers' diarrhea (103). A number of studies have also been performed on healthy volunteers (93-95,97-100,104,105). Ciprofloxacin is excreted in...

Canine And Feline Gastrointestinal Microbiota Gram Positive Intestinal Bacteria

Amongst Gram-positive bacteria residing in the gut, lactic acid bacteria (LAB) make up the largest and most important part of the intestinal microbiota. Although they have a significant protective function in the gut, the present knowledge of canine and feline Gram-positive intestinal microbiota is scant. Most of the canine LAB belong to the genera Streptococcus and Lactobacillus. In a recent study, Streptococcus alactolyticus was found to be a predominant culturable LAB in jejunal and fecal...

Short Chain Fatty Acid Production

Principal end products of bacterial fermentation in the colon are SCFA, i.e., acetate, propionate, and butyrate. Other fermentation products include ethanol, lactate, succinate, formate, valerate, and caproate. Branched chain fatty acids such as isobutyrate, 2-methyl-butyrate, and isovalerate may also be formed from the fermentation of amino acids. The production of SCFA by the intestinal microbiota serves to salvage energy from the digesta that would otherwise be lost for the host (90)....

Modifying The Microbial Metabolic Activity

Due to its numbers and taxonomic diversity, the intestinal microbiota has an enormous metabolic potential. The microbiota's metabolic activity is comparable to that of the liver, our metabolically most active organ. This metabolism has a pronounced influence on the health and well being of the host, as described in more detail in the chapter by Goldin. Probiotics have been shown to be able to change the metabolic activity of the intestinal microbiota. In part, this may relate to a direct change...

Assessment Of Microbiota Vitality And Metabolic Activity

The aforementioned molecular techniques have greatly contributed to our fundamental understanding of the biodiversity, establishment, succession and structure of the intestinal microbiota yet little is known about the in situ association between the microbial diversity and the metabolic activity of a phylogenetic affiliated group. A further challenge is to determine the physiological activity of the detected cells. This includes those cells that are naturally present within the ecosystem as...

Th1Th2 Balance

Several years ago Mosmann and coworkers (27) described different subsets of CD4 + T cells that differ by the cytokine profiles produced after activation (Fig. 1). Three kinds of T cells are now described from progenitor type 0 helper T cells (Th0). The type 1 helper T cells (Th1) mainly secrete IFN-y, a pro-inflammatory cytokine, and IL-2. Th1 induce a weak synthesis of Abs by B cells (subclass IgG2a) and are recruited more in the event of a cell-mediated response. In contrast, activation of...

Intestinal Bacterial Synthesis and Metabolism of Vitamins

The human intestinal bacteria can synthesize vitamin K, a member of the naphtoquinone family. The liver cannot synthesize the prothrombin complex, a blood-clotting factor, unless menaquinone, a substituted naphthoquinone, is present. The peptides that become the glycopeptides of the prothrombin complex require menaquinone for synthesis from the appropriate RNA codon. Bacteria found in the intestine can also synthesize homologues of menaquinone-7 (vitamin K2). The synthesized homologues range...

Self Opening Capsule

The Crosby capsule, first applied in 1957, was used to obtain biopsies from the small intestine before the introduction of the endoscope. This self-opening capsule is a metallic capsule of 19 to 11 mm with a round opening of 4 mm (53). A long tiny tube is attached to the capsule, and this is muscle loaded through an endoscope which is passed into the second part of the duodenum. Intestinal mucosa is sucked into the tube by suction and excised. Every part of the stomach and the small intestine...

In Vivo Expression Technology Approaches

The original IVET approach involves a tandem set of two promoterless reporter genes, namely purA and lacZ, which were used to identify promoters that are specifically switched on in Salmonella typhimurium during infection (35). Purine auxotroph mutants (DpurA) of Salmonella typhimurium were only able to survive in a mouse model system when complemented in trans with a plasmid encoded purA copy. The promoterless purA gene was thereby utilized as a reporter for the identification of chromosomal...

Regulation of the Immune Responses

Tolerance to Soluble Proteins Oral Tolerance The role of the intestinal microbiota on the OT process has been demonstrated by various experimental studies using GF mice. Results depend on the immune response considered, oral Ag, and experimental schedule used. In these experiments, immune responses to a specific Ag are compared in two groups of mice the tolerant group where mice are fed with an Ag prior to the peripheral immunization with the same Ag, and the control group fed with only the...

Chemically Induced Responses

Animals that have been intentionally exposed to specific pro-inflammatory or carcinogenic chemicals have been used in studies on the role of microbiota in the development of both cancer and IBD (Table 1). Cancer, or other malignant abnormalities in the gut mucosa, may be induced by the oral administration of carcinogens. Examples of such carcinogens are 1, 2 dimethylhydrazine (DMH), and N-methyl-N0-nitro-Nitrosogua-din (MNNG). These types of models, which are based on either CV or HFA animals,...

Possibilities and Limitations of Rumen Simulation Methods

The in vitro environmental conditions (temperature, pH, buffering capacity, osmotic pressure, dry matter content and oxidation-reduction potential) should represent as closely as possible those of the rumen. Irrespective of the technique applied, the quality of the inoculum is one of the most important aspects in rumen simulations. In most studies the rumen fluid is strained through two, sometimes even four layers of cheesecloth. As a result, the inoculum is likely to represent only the...

Crosstalk Between Bacteria And Intestinal Epithelial Cells

As discussed in chapter 5, some ingested probiotic bacteria have shown immunomodulatory properties (44-46). Both commensal and pathogenic bacteria possess recognized structures named pathogen-associated molecular patterns (PAMPS). These recognized structures are essential for the microbe, mostly constitutively expressed and shared by the same group of microorganisms. PAMPS that are characterized to date include N-formylated peptide (47), lipopolysaccharides (LPS) (48), and lipopeptides (49),...

Probing Strategies

As well as affording design of PCR primers for specific bacterial populations, the improved 16S rRNA gene sequence information has greatly enhanced the development of probing strategies for gut micro-organisms. Two probing strategies have generally been employed, namely, dot-blot hybridization and fluorescent in situ hybridization (FISH). The nature of the 16S rRNA gene of bacteria also enables development of oligonucleotide probes targeting different taxonomic levels, i.e., domain level (Bact...

Brief History Of The Development Of Bifidus Factors And Prebiotics

Bifidogenic or bifidus factors were recognized as early as 1954 with Gyorgy et al. (14,15) describing such components in milk and colostrum, including a range of amino sugars and non-glycosylated casein peptides. Glycoproteins from whey were also shown to have bifidogenic potential (16) along with lactoferrin (17,18). Bifidogenic effects have been reported for pantethine from carrot extracts (19,20) and for 2-amino-3-carboxy-1,4-naphthoquinone (ACNQ), a compound isolated from Propionibacterium...

Gnotobiotic Ruminants in Studies into the Microbiota of the Gastrointestinal Tract

Gnotobiotic ruminants can be used to observe the development of the rumen ecosystem as well as to study the relations between rumen and its microbiota. The rumen microbiota directly affects the development of the rumen epithelium and the level of intermediary metabolism by the action of rumen fermentation and its final metabolites. Fonty and coworkers (90), using meroxenic lambs demonstrated that the functions of the rumen and the stability of the ecosystem depended on the complexity and...

Types Of Intestinal Simulator Models

In vitro models can be divided into batch cultures, chemostat-type simulators, including semi-continuous and continuous cultures, and non-chemostat-type simulators. All models of the gastrointestinal tract (GIT) have strictly anaerobic conditions in order to simulate the environment that supports the growth of microbiota obtained from the GIT of humans or other mammals. In vitro models can be used sequentially, so that in the simulators of stomach and small intestine the food matrix can be...

Relationships Between The Intestinal Immune System And Intestinal Microbiota

The intestinal microbiota has marked influences on the intestinal and peripheral host's immunity. In some cases, the effects are produced by the whole intestinal microbiota, whereas in other cases only one predominant bacterium is capable of producing a certain immunostimulatory effect that is as effective as that of the whole microbiota. Moreover, the post-natal period seems to play a crucial role in the cross talk between the intestinal microbiota and the development of some important...

References

The Prolongation of Life. New York G. Putnam's Sons, 1908. 2. Tissier H. Traitement des infections intestinales par la methode de la flore bacterienne de l'intestin. Crit Rev Soc Biol 1906 60 359-361. 3. Kim HS, Gilliland SE. Lactobacillus acidophilus as a dietary adjunct for milk to aid lactose digestion in humans. J Dairy Sci 1983 66 959-966. 4. van Niel CW, Freudtner C, Garrison MM. Christakis, D.A. Lactobacillus therapy for acute infectious diarrhoea in children a...

Human Flora Associated Animals

The establishment of human fecal microbes within animals, provides the opportunity for the study of a microbiota of human origin within these animals. Human flora associated animals (HFA) have proven to be particularly valuable in studies of the metabolic and immunological activities of the human microbiota. Athough HFA animals are valuable for investigations related to the human microbiota, several differences between animal and human physiology may influence colonization by the human...

Microbial Degradation of Intestinal Enzymes

In the following section, trypsin is used as a model substance for endogenously derived enzymes. It is excreted as a precursor, trypsinogen, from the pancreas, and activated in the small intestine, mainly by brush border enzymes (36). Fecal tryptic activity represents the net sum of processes involving the secretion of trypsinogen, its activation to trypsin, trypsin inactivators, and the presence in the intestine of microbial- and diet-derived compounds and enzymes that inactivate or degrade...

Rumen Simulators

Fermenter Flask For Rumen Microbes

The artificial rumen techniques developed over the past five decades for investigation of rumen physiology as well as evaluation of feed rations, have ranged from batch fermentations to more complicated continuous incubations. In addition, the absorption function of the rumen wall has been included in some designs, in which a semi-permeable membrane is applied for removal of the fermentation end products. The most simplistic, in vitro fermentations representing the rumen were performed in...

Development Of Intestinal Microbiota In Dogs And Cats

Although there is paucity of research data concerning the development of intestinal microbiota of dogs and cats, it can be considered to follow a similar pattern as known for other mammals. Intestinal colonization is a gradual process starting immediately after birth. In newborn puppies and kittens the alimentary canal is sterile but is quickly inhabited by bacteria from birth canal and environment. The dam usually licks the newborn thoroughly thus transferring its own indigenous bacteria to...

Physiology and Microbiology of the GI Tract

Rat Grid Prevention Coprophagy

The human GIT is the most appropriate environment to conduct studies on the human GI microbiota but for practical reasons animal models are used extensively for these types of studies. The wide range of similarities between the animal and human GIT makes it possible to draw reasonable parallels between these two hosts, however, results from studies on the human microbiota in animals may not entirely reflect processes occurring in the human GIT. The reason for this is that there are also many...

Advantages over Probiotics

With the exception of some mechanisms of immunomodulation, the theoretical basis for many of the anticipated probiotic effects of bifidobacteria rely on the bacteria being viable in the intestinal tract. Currently, probiotics are limited by their stability largely to fresh food products such as fermented dairy products and juices, and nutraceutical products where they are formulated as dried powders. In contrast, prebiotics are stable, can be heat-processed, and can therefore be incorporated...

Microbial Conversion of Cholesterol to Coprostanol

Cholesterol is a component in all mammalian cellular membranes and a precursor of steroid hormones, vitamin D, and bile acids. Pathophysiologically, it is thought to be an important factor in the pathogenesis of atheromatous arterial disease, hypertension, cancer of the large bowel, and other disorders 8 . The intestinal cholesterol is derived mainly from two sources partly from synthesis occurring in the liver and the small intestine and partly from foods of animal origin. The main elimination...

Age Altered Aspects of the Intestinal Microbiota

Normal aging is associated with significant changes in the function of most organs and tissues, such as decreased taste thresholds, hypochlorhydria due to atrophic gastritis, and decreased liver blood flow and size 11 . The GI tract is no exception, and there is increased evidence of impaired gastrointestinal function with aging 3,11-13 . In the GI tract of the elderly, the age-related changes include decreased acid secretion by the gastric mucosa, and greater permeability of mucosal membranes...

Features Of The Gastrointestinal Tract Structure and Function of the Small Intestine

Villi Diagram

The small intestine is the principal site of food digestion, nutrient absorption as well as endocrine secretion. It is the longest component of the alimentary tract, measuring over 6 meters, and is divided into three anatomic regions duodenum, jejunum and ileum. The duodenum begins at the pylorus of the stomach and is the proximal 20-25 cm of the small intestine. The jejunum spans about 2.5 meters in length. The ileum is approximately 3.5 meters long and an extension of the jejunum. The...

Taxonomic Species Placement of Bifidobacteria Microbiota with

Bifidobacteria have been known since Tissier 5 first described a species from the feces of breast-fed infants, which was later named as Lactobacillus bifidus by Orla-Jensen 29 . Since that time numerous studies have been published concerning the ecology and importance of bifidobacteria in the intestine of humans, especially in infants. A new taxonomic system was established by creating the genus Bifidobacterium with the description of several new species besides B. bifidum, which was the only...

Microbiota And Gastrointestinal System Distribution of Microbiota

The mucosal surface of the human body, including the gastrointestinal tract, the respiratory tract and the urogenital tract, has a total surface area of more than 400 m2 11 . The gastrointestinal tract's surface area is about 200-300 m2 and is colonized by 1013-14 bacteria with hundreds of bacterial species and subspecies. The normal microbiota of the gastrointestinal tract has been grouped and defined into two categories, the autochthonous indigenous and the allochthonous nonindigenous species...

Mucus Adhesion of Bifidobacteria

The reason for the age-related decrease in bifidobacteria numbers is still not well understood. Adhesion to the intestinal mucosa is regarded as a prerequisite for colonization by microbes and induction of the healthy promotion by them. It has therefore been proposed as one of the selection criteria for probiotic strains 42-45 . Ouwehand and coworkers 46 tested four Bifidobacterium strains for adhesion to mucus isolated from subjects of different age groups including healthy newborns, 2- and...

Microbial Bile Acid Metabolism

In all mammals, bile acids are derived from cholesterol in the liver. Cholic acid and chenodeoxycholic acid are common, but many other primary bile acids may be found. The primary bile acids are conjugated, usually with taurine or glycine, sometimes also with sulphate or glucuronate, and excreted into the bile. In the intestinal tract, the conjugated primary bile acids are attacked by microbial enzymes and converted into a variety of metabolites. The so-called secondary bile acids thus formed...

Structure and Function of the Large Intestine

Large Intestine Problems

The large intestine is a continuation of the ileum and is usually divided into three regions the colon, rectum and anal canal. The colon accounts for nearly the full length of the large intestine. The colon absorbs water and electrolytes approximately 1400 ml per day . It also compacts and eliminates feces about 100 ml per day . Feces are composed of water 75 , dead bacteria 7 , roughage 5 , inorganic substances 5 , and undigested protein, dead cells and bile pigment 1 . Bacterial products,...

Studies by Traditional Plate Culture Methods

The first reports associating allergy with characteristic microbial composition in the gut appear to be from studies in the former Soviet Union in the early1980s 38-40 . One of these studies, reported also in English, involved an assessment of 60 under one-year-old infants with food allergy and atopic eczema. It was claimed that the severity of the disease was in direct correlation with the stage of aberrancy in the fecal microbiota. This aberrancy was characterized as low prevalence of...

Fecal Samples

Feces are a complex microbial habitat, with many niches occupied by bacteria. It is estimated that bacteria account for about 30 of the fecal mass, and 40-55 of fecal solids. All of the bacteria in feces are exposed to the influences of dehydrating and concentrating mechanisms of the colon and rectum, and intense biochemical activity of the organisms living in the material. When the samples consist of only feces, the composition and localization of communities anywhere in the tract cannot be...

Preface

The human gastrointestinal tract microorganisms, termed the microbiota, have been investigated since the beginning of microbiological studies, when Antonie van Leeuwenhoek, the father of microbiology, investigated the microorganisms in his own stools. The human microbiota comprises trillions of microbes distributed in various niches throughout the intestinal tract and is one of the most complex microbial ecosystems on earth. The host and its microbiota have co-evolved together, and considering...

Bacterial Metabolism of Androgens and Estrogens

Estrone, estradiol, and estriol are the three major estrogens that are excreted into the bile. These estrogens are conjugated to glucuronic acid and or sulfate. Upon excretion of these conjugated estrogens from the bile into the small intestine the conjugates are available substrates for bacterial metabolism. The bacteria of the lower small intestine and colon can hydrolyze the estrogen conjugate releasing free estrogens 45 . The nonconjugated estrogens are then subject to additional bacterial...

Bacterial Metabolism of Tyrosine and Tryptophan

Tyrosine and tryptophan are amino acids that can be converted by bacterial reactions in toxins and carcinogens. The tryptophanase containing Bacteroides thetaiotamicron, an organism found in the intestine, can convert tryptophan to indole a compound with carcinogenic activity 75 . Tyrosine is converted to phenol by aerobic intestinal bacteria, and to p-cresol by intestinal anaerobic bacteria. These metabolites of tyrosine are not found in the urine of germfree mice. Phenol and cresol have been...

Anatomy

Lamina Propria Galt

The immune system associated with the small intestine is currently described according to two compartments i the inducing sites, named the gut associated lymphoid tissue GALT , consisting of organized aggregated lymphoid tissue, scattered small nodules, Peyer's patches PPs , and mesenteric lymph nodes MLN and ii the effector sites, i.e., the lamina propria tissue where numerous mature B and T small lymphocytes 60 CD4 T cells , plasma cells of which about 90 synthesize IgA are present, and the...

Proanthocyanidins

Proanthocyanidins are dimers, oligomers, and polymers of flavan-3-ols and are formed by enzymatic or chemical condensation. These so-called condensed tannins contribute to astringent tastes in fruits e.g., grapes, peaches, apples, pears, berries etc. , beverages e.g., wine, cider, tea, beer etc. and chocolate. At a lower degree of polymerization they are colorless and bitter to taste, but with greater polymerization the taste becomes astringent and the color yellow to brown. Proanthocyanidins...

Effects of Bifidobacteria Probiotics on Immunosenescence

Probiotics have been defined as a live microbial food ingredient that are beneficial to the health of the host 65,66 . Most current probiotics are lactic acid bacteria, especially Lactobacillus and Bifidobacterium species 66 . Among the proposed health-promoting effects of the probiotic strains are the enhancement of cell-mediated immune responses of the host by stimulating the pro-inflammatory cytokine, particularly IL-12 67,68 . The cell-mediated immune response, enhanced by the...

Biopsy

To investigate the gastric microbiota, tissue is generally obtained by an endoscopic biopsy. Slightly less invasive methods are available to obtain a specimen such as the use of a small bowel biopsy tube or capsule, or biopsy forceps that can be passed through a modified nasogastric tube positioned either in the gastric body or antrum. A biopsy is clinically unnecessary to diagnose H. pylori via microbiological methods unless one wishes to isolate the organism for antibiotic susceptibility...

Full Thickness Biopsy

Full thickness biopsy is a peroperative or laparoscopic biopsy muscularis-containing biopsy used to diagnose motility disturbances. One incision is situated below the umbilicus, and one in the left fossa. The bowel loop is identified laparoscopically, and will then be exteriorized through the incision below the umbilicus. The full thickness biopsy of at least 10X10 mm will then be taken with a surgical knife. The bowel loop is closed with absorbable sutures, and repositioned into the abdomen 56...

Intestinal Bacterial Metabolism of Bile Acids and Bile Pigments

Cholesterol is a precursor of bile acids, and both are synthesized in the liver from two carbon units. Bile acids synthesized in the liver are conjugated through an amide bond to either glycine or taurine. The conjugated bile acids are deposited in the bile, and excreted into the upper small intestine. The bacterial conversion of bile acids primarily occurs in the distal ileum and colon. The bacterial reactions on bile acids include the hydrolysis of the amide bond to release free bile acids...

Acquisition Of The Gut Microbiota

Acquisition of the normal microbiota is a biological succession which commences during or immediately following birth depending on the mode of delivery . During natural birth, the neonate is exposed to the maternal microbiota, both vaginal and fecal 22-24 . However, colonization is delayed in infants born via Caesarian section and the major source of inoculation is thought to be from the environment including nosocomially from within the maternity ward 23 . Caesarean section delivery has been...

Contributors

Akkermans Department of Surgery, Utrecht University Medical Center, Utrecht, The Netherlands Kaouther Ben Amor Laboratory of Microbiology, Wageningen University, Wageningen, The Netherlands Malik M. Anwar Alimentary Pharmabiotic Centre, Departments of Medicine and Surgery, Microbiology, National Food Biotechnology Centre, National University of Ireland, Cork, Ireland Max Bingham Unilever Research and Development, Vlaardingen, The Netherlands Alojz Bomba Institute of Gnotobiology and...

Glycocholate Breath Test

14C-glycocholate breath test or bile acid test is based on the bile salt deconjugating capacity of bacteria in the proximal small bowel. Conjugated bile acids are excreted through the bile in the duodenum, and they are reabsorbed in the terminal ileum. Conjugated bile acids are in the enterohepatic circulation. Physiologically, less than 5 of the conjugated bile acids reach the colon. After excretion in the duodenum, bile acids stimulate micellization of dietary lipids. After oral...

Colonization And Succession Of Human Intestinal Microbiota With

The gastrointestinal tract GI tract serves as one of the biggest interfaces between the body and the external environment 3 . This GI tract is a highly specialized organ system that allows us to consume food in discrete meals as well as a very diverse array of foodstuffs to meet our nutrient needs. The organs of the GI tract include the oral cavity, esophagus, stomach, small and large intestine in addition, the pancreas and liver secrete into the small intestine. The system is connected to the...