In vivo and in vitro effects of tea extracts on enterotoxigenic Escherichia coli-induced intestinal fluid loss in animal models

Review: Harmonised in vitro digestion and the Ussing chamber for investigating the effects of polyphenols on intestinal physiology in monogastrics and ruminants

Because of the relevant effects of plant-derived polyphenols (PPs) on monogastrics and ruminants' nutrition, emissions and performance, an increasing number of in vivo and in vitro studies are being performed to better understand the mechanisms of action of polyphenols at both the ruminal and intestinal levels. The biological properties of these phenolic compounds strongly depend on their degradation, absorption and metabolism. The harmonised in vitro digestion method (INFOGEST) is one of the most reliable in vitro methods used to assess the bioaccessibility and or antioxidant activity of PP contained in different matrixes, as well as the interactions of PP and their degradation products with other feed ingredients. The effects of PP released from their matrix after in vitro digestion on different intestinal physiological parameters, such as epithelium integrity, can be further evaluated by the use of ex vivo models such as the Ussing chamber. This review aims to describe the combination of the INFOGEST method, coupled with the Ussing chamber as a valuable model for the digestion and subsequent effects and absorption of phenolic compounds in monogastrics and potentially in ruminants. The advances, challenges and limits of this approach are also discussed.

Anti-Bacterial, Anti-Diarrheal, and Cytotoxic Activities of Edible Fruits in the Sundarbans Mangrove Forest of Bangladesh

This study evaluated anti-bacterial, anti-diarrheal, and cytotoxic activities of ten edible fruits (Aegiceras corniculatum, Avicennia officinalis, Bruguiera gymnorrhiza, Ceriops decandra, Heritiera fomes, Nypa fruticans, Phoenix paludosa, Sarcolobusglobosus, Sonneratia caseolaris, and Xylocarpus mekongensis) in the Sundarbans mangrove forest of Bangladesh. Highest antibacterial activity was shown for ethanol:methanol (1:1) extracts of S. caseolaris (2 mg/disc), which demonstrated inhibition zones of 16.7, 17.0, 14.7, 15.7, and 15.7 mm against Escherichia coli, Klebsiella sp., Shigella boydii, Shigella sonnei, and Staphylococcus aureus, respectively. In mice with castor oil-induced diarrhea, S. caseolaris extract (250 mg/kg body weight) showed the highest inhibition (87.7%) and delayed the onset time (273 min) of diarrheal episodes, followed by A. corniculatum extract (inhibition, 83.6%; delayed onset time, 187.4 min). S. caseolaris and A. corniculatum fruit powders were successively fractionated into n-hexane, diethyl ether, chloroform, ethanol, and methanol. Antidiarrheal activity significantly increased with increasing polarity of these fractions. In brine shrimp lethality assay, S. globosus extract demonstrated the highest cytotoxicity (59.2 μg/mL), followed by H. fomes (74.1 μg/mL) and C. decandra (116.7 μg/mL); however, lowest cytotoxicity was shown for A. corniculatum, A. officinalis, and S. caseolaris extracts. Mice treated with A. corniculatum extract did not experience any acute toxicity. These results demonstrate that S. caseolaris and A. corniculatum fruits have potential to treat diarrhea and may act as useful nutraceuticals.

Identifying the mechanism of eriosematin E from Eriosema chinense Vogel. for its antidiarrhoeal potential against Shigella flexneri-induced diarrhoea using in vitro, in vivo and in silico models

The main objective of the present investigation was to mechanistically evaluate the potency of the root extract (EEC), its bioactive chloroform fraction (CEC) and eriosematin E (ECM) isolated from Eriosema chinense against Shigella flexneri-induced sub-chronic model of infectious diarrhoea using in vitro, in vivo, and in silico methods. The in vitro antibacterial activity against pathogenic strain of S. flexneri demonstrated maximum effect of ECM followed by CEC and EEC in inhibiting growth of bacteria. Further, for in vivo evaluation, was carried out by inducing diarrhoea to the rats by administering oral suspension of S. flexneri to the animals, which was followed by treatment for a period of 6 days. EEC at 200, CEC at 100 and ECM at 10 mg/kg, p.o. showed promising effect, where EEC and ECM were found to be more effective showing maximum % protection on 6th day. Results also demonstrated a significant restoration of altered antioxidants, pro-inflammatory cytokines (IL-1β and TNF-α) expression, electrolyte balance, Na⁺/K⁺-ATPase activity and was also supported by histopathological examinations. Molecular docking study revealed that, eriosematin E inactivated the protease activity of SepA, a protein secreted by Shigella, which is responsible for disruption of epithelial barrier integrity. Thus, the overall observation confirmed the role of eriosematin E from E. chinense in treatment of Shigella flexneri-induced infectious diarrhoea.

The antidiarrhoeal evaluation of Psidium guajava L. against enteropathogenic Escherichia coli induced infectious diarrhoea

ETHNOPHARMACOLOGICAL RELEVANCE

The plant Psidium guajava L. (Myrtaceae), commonly used as an edible fruit is traditionally used worldwide in treatment of various gastrointestinal problems including diarrhoea. The leaves of the plant have also been evaluated for antidiarrhoeal activity in various chemical induced diarrhoea models.

OBJECTIVE

The main objective of the present study was to evaluate the potency of P. guajava leaves and its major biomarker quercetin against enteropathogenic Escherichia coli (EPEC) induced infectious diarrhoea using preclinical and computational model.

MATERIAL AND METHODS

P. guajava alcoholic leaf extract (PGE) was initially standardized using HPLC taking quercetin as a biomarker and was then subjected to antidiarrhoeal evaluation on rats in an EPEC induced diarrhoea rat model. The study included assessment of various behavioral parameters, initially for 6 h and then for up to 24 h of induction which was followed by estimation of stool water content, density of EPEC in stools and blood parameters evaluation. The colonic and small intestinal tissues of the treated animals were subjected to various biochemical estimations, in vivo antioxidant evaluation, estimation of ion concentration, Na⁺/K⁺-ATPase activity, assessment of pro-inflammatory cytokines and histopathological studies. Further, the major biomarker off PGE, quercetin was subjected to molecular docking studies with Na⁺/K⁺-ATPase and EPEC.

RESULTS

The results demonstrated a significant antidiarrhoeal activity of quercetin (50 mg/kg), PGE at 200 and 400 mg/kg, p.o., where quercetin and PFGE at 200 mg/kg, p.o. were found to be more prominent, as confirmed through higher % protection, water content of stools and density of EPEC in stools. PGE and its biomarker quercetin also significantly recovered the WBC, Hb, platelets loss and also revealed a significant restoration of altered antioxidants level, pro-inflammatory cytokines (IL-1β and TNF-α) expression and had positive influence on Na⁺/K⁺-ATPase activity. The docking studies of quercetin with Na⁺/K⁺-ATPase showed favourable interactions and residues Glu 327, Ser 775, Asn 776, Glu 779 and Asp 804 of Na⁺/K⁺-ATPase were adequately similar to quercetin for donating ligands for binding, while quercetin was also found to terminate the linkage between mammalian cells and EPEC thus, preventing further infection from EPEC.

CONCLUSION

Inhibition in intestinal secretion, reduced nitric oxide production and inflammatory expression along with reactivation of Na⁺/K-ATPase activity could be attributed to the observed antidiarrhoeal potential of PGE against infectious diarrhoea, where quercetin was confirmed to be the main contributing factor.

Anti-virulence activity of polyphenolic fraction isolated from Kombucha against Vibrio cholerae

The use of traditional foods and beverages or their bioactive compounds as anti-virulence agents is a new alternative method to overcome the increased global emergence of antimicrobial resistance in enteric pathogens. In the present study, we investigated the anti-virulence activity of a polyphenolic fraction previously isolated from Kombucha, a 14-day fermented beverage of sugared black tea, against Vibrio cholerae O1. The isolated fraction was mainly composed of the polyphenols catechin and isorhamnetin. The fraction, the individual polyphenols and the combination of the individual polyphenols significantly inhibited bacterial swarming motility and expression of flagellar regulatory genes motY and flaC, even at sub-inhibitory concentrations. The polyphenolic compounds also decreased bacterial protease secretion and mucin penetration in vitro. In vivo study revealed that the polyphenolic fraction significantly inhibited V. cholerae induced fluid accumulation in the rabbit ileal loop model and intestinal colonization in suckling mice model. Therefore, the anti-virulence activity of the Kombucha polyphenolic fraction involved inhibition of motility and protease secretion of V. cholerae, thus preventing bacterial penetration through the mucin layer as well as fluid accumulation and bacterial colonization in the intestinal epithelial cells. The overall results implied that Kombucha might be considered as a potential alternative source of anti-virulence polyphenols against V. cholerae. To the best of our knowledge, this is the first report on the anti-virulence activity of Kombucha, mostly attributed to its polyphenolic content.

Quercetin a major biomarker of Psidium guajava L. inhibits SepA protease activity of Shigella flexneri in treatment of infectious diarrhoea

The leaves of the plant Psidium guajava L. (Myrtaceae) has been traditionally used in treatment of various gastrointestinal disorders including diarrhoea and have also been reported for its potent antidiarrhoeal activity on various chemical induced diarrhoea models. The objective of our present study was to evaluate the potency of the leaf extract of the plant Psidium guajava (PGE) along with its major biomarker quercetin against Shigella flexneri-induced sub chronic model of infectious diarrhoea. PGE at 100, 200 and 400 mg/kg, p.o. and quercetin at 50 mg/kg, p.o. were administered to Shigella flexneri-induced diarrhoeal rats for five days and various behavioural parameters were evaluated on 1st, 3rd and 5th day of treatment. This was followed by assessment of stool water content, density of Shigella flexneri in stools and blood parameters examination. After treatment, colon and small intestine of rats was dissected and subjected to biochemical estimations, cytokine profiling, antioxidant evaluations, ion concentration determination, Na⁺/K⁺-ATPase activity and histopathology. Molecular docking studies on crystal structure of Secreted Extracellular Protein A (SepA) from Shigella flexneri with biomarker quercetin was also performed. PGE at 200 mg/kg followed by quercetin depicted maximum antidiarrhoeal potential, which was confirmed through diarrhoea score and % protection, while PGE at 400 mg/kg showed similar effect to PGE 200 mg/kg thus, the later may have ceiling effect. PGE and quercetin also significantly reduced the density of Shigella flexneri in stools, water content of stools and restored the alterations observed in blood parameters, antioxidant status and pro-inflammatory cytokines (IL-6 and TNF-α) expression. These parameters contributed in normalization of electrolyte balance, reactivation of Na⁺/K⁺-ATPase activity and repairing of epithelial tissue damage, confirmed through histopathology. Docking simulation studies revealed the role of quercetin in inactivating the protease activity of SepA, a protein secreted by Shigella, which disrupts epithelial barrier integrity during infection and also manages its signal production. Thus, the overall results confirmed the role of quercetin as a major biomarker for the observed antidiarrhoeal potential of P. guajava against Shigella flexneri induced infectious diarrhoea.

The potency of eriosematin E from Eriosema chinense Vogel. against enteropathogenic Escherichia coli induced diarrhoea using preclinical and molecular docking studies

The main objective of the present study was to evaluate the potential of eriosematin E (ECM) isolated from the roots of Eriosema chinense against enteropathogenic Escherichia coli (EPEC) induced diarrhoea. ECM isolated from the bioactive chloroform fraction of E. chinense was subjected to antidiarrhoeal evaluation on rats against diarrhoea, induced by the oral suspension of EPEC. The study included evaluation of behavioral parameters for 6 h and up to 24 h of induction, followed by estimation of water content, the density of EPEC in stools and evaluation of various blood parameters. Further, the colonic and small intestinal tissues were subjected to biochemical estimations, antioxidant evaluation, determination of ion concentration, Na⁺/K⁺ -ATPase activity, pro-inflammatory cytokines assessment and histopathology. Finally, the impact of ECM on Na⁺/K⁺-ATPase was studied through molecular docking studies. Significant antidiarrhoeal potential of ECM was demonstrated at 5 and 10 mg/kg, p.o., however, ECM at 10 mg/kg, p.o. was found to be more effective, as confirmed through higher % protection, density of EPEC in stools and water content of stools. ECM also significantly increased the level of WBC, Hb, platelets and revealed restoration of altered antioxidants, pro-inflammatory cytokines (IL-1β and TNF-α) status and also reactivated the suppressed Na⁺/K⁺-ATPase activity, which was also confirmed through docking studies showing H-bonding of hydroxyl group of ECM with amino acids Asp 190, Asn 167 and Glu 169 thus, maintaining proper electrolyte balance and also prevented epithelial tissue damage. The overall effect of ECM may be attributed to the decline in the elevated level of cytokines, inhibition in nitric oxide production and reactivation of Na⁺/K⁺-ATPase activity resulting in reduced intestinal secretion.

Dietary Factors in Prevention of Pediatric Escherichia coli Infection: A Model Using Domestic Piglets

Enterotoxigenic Escherichia coli (ETEC) is the major etiological agent causing acute watery diarrhea that is most frequently seen in young children in lower-income countries. The duration of diarrheal symptom may be shortened by antibiotic treatment, but ETEC is relative refractory to common antibiotics. Burgeoning evidence suggests bioactive components that naturally occur in human milk (e.g., lysozyme and oligosaccharides) and plants (e.g., nondigestible carbohydrates and phytochemicals) contain antimicrobial functions are promising preventive measures to control ETEC infection. Although the exact protective mechanisms may vary for each compound and are still not completely understood, they generally act to (1) competitively inhibit the binding of pathogenic bacteria and toxins to gut epithelium; (2) directly kill pathogens; and (3) stimulate and/or enhance host mucosal and systemic immune defense against pathogenic microorganisms. An appropriate ETEC-challenge animal model is critical to evaluate the effect and unveil the mechanism of bioactive compounds in prevention of enteric infection. Despite wide application in biomedical research, rodents do not usually manifest typical clinical signs of enteric infections. The remarkable differences in digestive physiology, immune response, and gut microbiota between rodents and human beings necessitate the use of alternative animal models. Pigs are closely related to humans in terms of genomes, physiology, anatomy of gastrointestinal tracts, digestive enzymes, components of immune system, and gut microbiota. Like human infants and young children, nursing and nursery piglets are more susceptible to ETEC infection and reproduce the clinical signs as observed in humans. Hence, the ETEC-challenge piglet represents a valuable translational model to study pathogenesis and evaluate dietary factors (e.g., milk bioactive compounds, nondigestible carbohydrates, and phytochemicals) as preventive measures for ETEC infection in pediatrics.

Agrimonia procera exerts antimicrobial effects, modulates the expression of defensins and cytokines in colonocytes and increases the immune response in lipopolysaccharide-challenged piglets

Background

Because antibiotic use in livestock is assumed to contribute to the emerging public health crisis of antibiotic resistance, alternatives are required. Phytogenic additives are extensively studied due to their antibiotic properties. Components of Agrimonia species have been reported as candidate antimicrobials that possess antioxidative and anti-inflammatory properties. We studied the impact of Agrimonia procera (AP) on the growth of selected strains of gut bacteria, the effect of AP on the mRNA abundance of genes involved in inflammation and bacterial defense in a colon carcinoma cell line, the effect of AP in piglets challenged with lipopolysaccharides, and the effect of AP on the growth performance of healthy piglets.

Results

The in vitro growth rate of different bacteria strains was negatively affected by AP, especially in Pediococcus pentosaceus and all tested E. coli strains. Stimulation of Caco-2 cells with TNFα resulted in elevated mRNA expression of CXCL1, IL-8 and GPX2. After pretreatment of cells with AP, stimulation of Caco-2 cells with TNFα still resulted in elevated mRNA expression of CXCL1 and IL-8 at all measured points in time. However, mRNA expression in AP-pretreated cells was lower after 6 h and 24 h. In addition, expression of DEFB1 and GPX2 was significantly elevated after TNFα stimulation. In vivo, application of lipopolysaccharides induced significantly increased animal body temperatures. Piglets pretreated with AP prior to lipopolysaccharide application showed a faster and larger increase in body temperature than controls. In addition, piglets pretreated with AP appeared to release more TNFα than controls. In healthy piglets, AP treatment had no impact on growth performance parameters. Fecal dry matter and total plasma antioxidant capacity tended to be higher in piglets treated with AP than in control piglets (P = 0.055 and P = 0.087, respectively).

Conclusions

AP has antimicrobial effects in vitro and stimulated the expression of proinflammatory cytokines in Caco-2 cells. The additive had no effect on growth in healthy piglets but increased the immune response in LPS-treated animals. In addition, AP appeared to have antioxidative effects in vivo. Therefore, AP merits testing as a future alternative to antibiotics in animal husbandry.

Aquaporin-4 Is Downregulated in the Basolateral Membrane of Ileum Epithelial Cells during Enterotoxigenic Escherichia coli-Induced Diarrhea in Mice

Enterotoxigenic Escherichia coli (ETEC) are opportunistic pathogens that colonize the small intestine, produce enterotoxins and induce diarrhea. Some aquaporins (AQPs), such as AQP3 and AQP8, have been reported to participate in diarrhea by decreasing cellular influx in the gastrointestinal (GI) tract. AQP4 is another important water channel in the GI tract, but its role in ETEC-induced diarrhea has not been reported. Here, we demonstrated the potential roles of AQP4 in ETEC-induced diarrhea. Reverse transcription-polymerase chain reaction (RT-PCR) and western blotting showed that AQP4 was expressed in the mouse ileum, but not in the duodenum or jejunum while immunohistochemical staining showed that AQP4 localized to the basolateral membrane of ileum epithelial cells. Using an ETEC-induced mice diarrhea model, we demonstrated that both AQP4 mRNA level and the AQP4 protein level in the ileum decreased gradually over a time course of 7 days. These results suggest that AQP4 plays a role in the pathogenesis of ETEC-induced diarrhea by mediating water transport.

Aquaporin-3 is down-regulated in jejunum villi epithelial cells during enterotoxigenic Escherichia coli-induced diarrhea in mice

Enterotoxigenic Escherichia coli (ETEC)-induced diarrhea is a complex pathological process, involving ion channel regulation and water efflux. While the mechanism underlying water efflux in ETEC-induced diarrhea is still largely unknown, aquaporins (AQPs) play important roles in transcellular water movement, but their expression profile has not been demonstrated in the murine small intestine. We identified AQP3 expression in the jejunum, but not the duodenum or ileum, using reverse transcription PCR and western blotting. Immunohistochemistry showed that AQP3 localized to the jejunum villi epithelial cells. Using an ETEC-induced murine diarrhea model, we demonstrated that both AQP3 mRNA expression and protein concentration in the jejunum were gradually but significantly decreased over 7 d compared with controls. These results suggested impaired water influx also plays an important role in ETEC-induced diarrhea.

Effects of Ex Vivo Infection with ETEC on Jejunal Barrier Properties and Cytokine Expression in Probiotic-Supplemented Pigs

BACKGROUND AND AIM

Enterotoxigenic Escherichia coli (ETEC) strains are involved in piglet post-weaning diarrhea. Prophylactic measures including probiotics have been examined in infection experiments with live piglets. In the present study, we have tested whether the early effects of ETEC infection can also be evoked and studied in a model in which ETEC is added to whole mucosal tissues ex vivo, and whether this response can be modulated by prior supplementation of the piglets with probiotics.

METHODS

Jejunal barrier and transport properties of Enterococcus faecium-supplemented or control piglets were assessed in Ussing chambers. Part of the epithelia was challenged with an ETEC strain at the mucosal side. Fluxes of fluorescein as a marker of paracellular permeability, and the expression of selected tight junction (TJ) proteins and of proinflammatory cytokines were measured.

RESULTS

The addition of ETEC ex vivo induced an increase in transepithelial resistance peaking in the first 2 h with a concomitant reduction in fluorescein fluxes, indicating tightening effects on barrier function. The response of short-circuit current after stimulation with PGE₂ or glucose was reduced in epithelia treated with ETEC. ETEC induced a decrease in the TJ protein claudin-4 in the control diet group after 280 min and an increase in the mRNA expression of the proinflammatory cytokines interleukin-8 and TNF-α in both groups after 180 min.

CONCLUSIONS

The addition of ETEC ex vivo affected barrier function and transport properties of the jejunal tissues and enhanced cytokine expression. The differences in claudin-4 expression in the jejunum might indicate a beneficial effect of E. faecium prefeeding.

Cranberry extract inhibits in vitro adhesion of F4 and F18+Escherichia coli to pig intestinal epithelium and reduces in vivo excretion of pigs orally challenged with F18+ verotoxigenic E. coli

F4⁺E. coli and F18⁺E. coli infections are an important threat for pig industry worldwide. Antibiotics are commonly used to treat infected piglets, but the emerging development of resistance against antibiotics raises major concerns. Hence, alternative therapies to prevent pigs from F4⁺E. coli and F18⁺E. coli infections need to be developed. Since cranberry previously showed anti-adhesive activity against uropathogenic E. coli, we aimed to investigate whether cranberry extract could also inhibit binding of F4⁺E. coli and F18⁺E. coli to pig intestinal epithelium. Using the in vitro villus adhesion assay, we found that low concentrations of cranberry extract (20μg or 100μg/ml) have strong inhibitory activity on F4⁺E. coli (75.3%, S.D.=9.31 or 95.8%, S.D.=2.56, respectively) and F18⁺E. coli adherence (100% inhibition). This effect was not due to antimicrobial activity. Moreover, cranberry extract (10mg or 100mg) could also abolish in vivo binding of F4 and F18 fimbriae to the pig intestinal epithelium in ligated loop experiments. Finally, two challenge experiments with F18⁺E. coli were performed to address the efficacy of in-feed or water supplemented cranberry extract. No effect could be observed in piglets that received cranberry extract only in feed (1g/kg or 10g/kg). However, supplementation of feed (10g/kg) and drinking water (1g/L) significantly decreased excretion and diarrhea. The decreased infection resulted in a decreased serum antibody response indicating reduced exposure to F18⁺E. coli.

Effects of green tea on Escherichia coli as a uropathogen

Escherichia coli is the most common cause of urinary tract infections. The development of antibiotic resistance in E. coli is an important problem. Finding alternative antimicrobial agents from plant extracts has received growing interest. Camellia sinensis is a safe, nontoxic, cheap beverage that has been reported to have antimicrobial effects against various pathogenic bacteria including E. coli. Polyphenolic components of green tea ( lǜ chá) have antibacterial activity. Catechins also have synergistic effect with antibiotics such as chloramphenicol, amoxicillin, sulfamethoxazole, azithromycin, levofloxacin, gentamycin, methicillin, naldixic acid, and, especially ciprofloxacin. In this review, all experimental studies that evaluated the effect of green tea on E. coli were collected. Data from in vitro studies on the antimicrobial effects of green tea are promising, but human data are currently lacking. In vivo studies on antibacterial effects of green tea and evaluating the efficacy of its catechins in the treatment of urinary tract infection are needed.

Exopolysaccharides synthesized by Lactobacillus reuteri protect against enterotoxigenic Escherichia coli in piglets

Enterotoxigenic Escherichia coli (ETEC) is a major cause of diarrhea in piglets; ETEC cells colonize the intestinal mucosa with adhesins and deliver toxins that cause fluid loss. This study determined the antiadhesive properties of bacterial exopolysaccharides (reuteran and levan) and related glycans (dextran and inulin) in a small intestinal segment perfusion (SISP) model. The SISP model used 10 jejunal segments from 5-week-old piglets. Five segments were infected with ETEC expressing K88 fimbriae (ETEC K88), while five segments were treated with saline. Every two segments (ETEC and non-ETEC infected) were infused with 65 ml of 10 g liter(-1) of glycans or saline (control) for 8 h. High-resolution melting-curve (HRM) quantitative PCR (qPCR) indicated that E. coli is the dominant bacterium in infected segments, while other bacteria were predominant in noninfected segments. Infection by ETEC K88 was also verified by qPCR; gene copy numbers of K88 fimbriae and the heat-labile toxin (LT) in mucosal scrapings and outflow fluid of infected segments were significantly higher than those in noninfected segments. Genes coding for K88 fimbriae and LT were also detected in noninfected segments. LT amplicons from infected and noninfected segments were 99% identical over 481 bp, demonstrating the presence of autochthonous ETEC K88. All glycans reduced fluid loss caused by ETEC K88 infection. Reuteran tended (P = 0.06) to decrease ETEC K88 levels in mucosal scraping sample, as judged by qPCR. Fluorescent in situ hybridization analysis demonstrated that reuteran significantly (P = 0.012) decreased levels of adherent ETEC K88. Overall, reuteran may prevent piglet diarrhea by reducing adhesion of ETEC K88.

Interactions of black tea polyphenols with human gut microbiota: implications for gut and cardiovascular health

Epidemiologic studies have convincingly associated consumption of black tea with reduced cardiovascular risk. Research on the bioactive molecules has traditionally been focused on polyphenols, such as catechins. Black tea polyphenols (BTPs), however, mainly consist of high-molecular-weight species that predominantly persist in the colon. There, they can undergo a wide range of bioconversions by the resident colonic microbiota but can in turn also modulate gut microbial diversity. The impact of BTPs on colon microbial composition can now be assessed by microbiomics technologies. Novel metabolomics platforms coupled to de novo identification are currently available to cover the large diversity of BTP bioconversions by the gut microbiota. Nutrikinetic modeling has been proven to be critical for defining nutritional phenotypes related to gut microbial bioconversion capacity. The bioactivity of circulating metabolites has been studied only to a certain extent. Bioassays dedicated to specific aspects of gut and cardiovascular health have been used, although often at physiologically irrelevant concentrations and with limited coverage of relevant metabolite classes and their conjugated forms. Evidence for cardiovascular benefits of BTPs points toward antiinflammatory and blood pressure-lowering properties and improvement in platelet and endothelial function for specific microbial bioconversion products. Clearly, more work is needed to fill in existing knowledge gaps and to assess the in vitro and in vivo bioactivity of known and newly identified BTP metabolites. It is also of interest to assess how phenotypic variation in gut microbial BTP bioconversion capacity relates to gut and cardiovascular health predisposition.

Antibacterial and antidiarrheal activities of plant products against enterotoxinogenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) produces two types of enterotoxins: heat-labile (LT) and heat-stable (STa and STb). These molecules are involved in the induction of secretory diarrhea in animals including humans. This condition is currently treated using a fluid replacement therapy and antibiotics. This treatment is often not available to people in developing countries, and several die from the condition provoke by ETEC. Over the years, plants and plant extracts have been use as traditional medicine to treat various gastrointestinal ailments including diarrhea. Many of these plant products have been claimed to be active against diarrhea, however few have been extensively studied. The main objective of this review was to gather the scattered information on the antidiarrheal activities reported for various plant products on ETEC. This includes two major effects: (1) The inhibitory effect on bacterial growth or viability and (2) The interference with ETEC enterotoxins activity upon the intestinal epithelium. We will focus on plant products and extracts for which we have major indications of their biological activity against ETEC and their enterotoxins. Because Vibrio cholerae toxin (CT) is structurally, antigenically and mechanistically related to LT, it will also be discussed in this review.

Use of pigs as a potential model for research into dietary modulation of the human gut microbiota

The human intestinal microbial ecosystem plays an important role in maintaining health. A multitude of diseases including diarrhoea, gastrointestinal inflammatory disorders, such as necrotising enterocolitis (NEC) of neonates, and obesity are linked to microbial composition and metabolic activity. Therefore, research on possible dietary strategies influencing microbial composition and activity, both preventive and curative, is being accomplished. Interest has focused on pre- and probiotics that stimulate the intestinal production of beneficial bacterial metabolites such as butyrate, and beneficially affect microbial composition. The suitability of an animal model to study dietary linked diseases is of much concern. The physiological similarity between humans and pigs in terms of digestive and associated metabolic processes places the pig in a superior position over other non-primate models. Furthermore, the pig is a human-sized omnivorous animal with comparable nutritional requirements, and shows similarities to the human intestinal microbial ecosystem. Also, the pig has been used as a model to assess microbiota–health interactions, since pigs exhibit similar syndromes to humans, such as NEC and partly weanling diarrhoea. In contrast, when using rodent models to study diet–microbiota–health interactions, differences between rodents and humans have to be considered. For example, studies with mice and human subjects assessing possible relationships between the composition and metabolic activity of the gut microbiota and the development of obesity have shown inconsistencies in results between studies. The present review displays the similarities and differences in intestinal microbial ecology between humans and pigs, scrutinising the pig as a potential animal model, with regard to possible health effects.

Tea: A native source of antimicrobial agents

Tea (Camellia sinensis) is one of the most popular nonalcoholic beverages, consumed by over two-thirds of the world's population because of its refreshing, mild stimulant and medicinal properties. It is processed in different ways in different parts of the world to give green, black, oolong, and pu-erh tea. Among all tea polyphenols, epigallocatechin-3-gallate has been responsible for much of the health promoting abilities of tea including anti-inflammatory, antimicrobial, antitumour, anti-oxidative, protection from cardiovascular disease, anti-obesity, and anti-aging properties. In the present review, the antibacterial, antiviral, and antifungal activities of different types of tea and their polyphenols are reported, highlighting their mechanisms of action and structure–activity relationship. Moreover, considering that the changing patterns of infectious diseases and the emergence of microbial strains resistant to current antibiotics, there is an urgent need to find out new potent antimicrobial agents as adjuvants to antibiotic therapy. The synergistic effect of tea polyphenols in combination with conventional antimicrobial agents against clinical multidrug-resistant microorganisms has also been discussed in this review.

Can scientific evidence support using Bangladeshi traditional medicinal plants in the treatment of diarrhoea? A review on seven plants

Diarrhoea is a common disease which causes pain and may be deadly, especially in developing countries. In Bangladesh, diarrhoeal diseases affect thousands of people every year, and children are especially vulnerable. Bacterial toxins or viral infections are the most common cause of the disease. The diarrhoea outbreaks are often associated with flood affected areas with contaminated drinking water and an increased risk of spreading the water-borne disease. Not surprisingly, plants found in the near surroundings have been taken into use by the local community as medicine to treat diarrhoeal symptoms. These plants are cheaper and more easily available than conventional medicine. Our question is: What is the level of documentation supporting the use of these plants against diarrhoea and is their consumption safe? Do any of these plants have potential for further exploration? In this review, we have choosen seven plant species that are used in the treatment of diarrhoea; Diospyros peregrina, Heritiera littoralis, Ixora coccinea, Pongamia pinnata, Rhizophora mucronata, Xylocarpus granatum, and Xylocarpus moluccensis. Appearance and geographical distribution, traditional uses, chemical composition, and biological studies related to antidiarrhoeal activity will be presented. This review reveals that there is limited scientific evidence supporting the traditional use of these plants. Most promising are the barks from D. peregrina, X. granatum and X. moluccensis which contain tannins and have shown promising results in antidiarrhoeal mice models. The leaves of P. pinnata also show potential. We suggest these plants should be exploited further as possible traditional herbal remedies against diarrhoea including studies on efficacy, optimal dosage and safety.

Evaluation of pharmacological activities, cytotoxicity and phenolic composition of four Maytenus species used in southern African traditional medicine to treat intestinal infections and diarrhoeal diseases

BACKGROUND

Microbial infections and resulting inflammation and oxidative stress are common pathogenesis of gastrointestinal tract (GIT) disorders. In South Africa, several species of the genus Maytenus are used in traditional medicine to treat various infectious diseases. Most of the previous work on this genus was focused on nonpolar extracts from the root and bark. In this study, leaf extracts of polar extracts of Maytenus peduncularis, Maytenus procumbens, Maytenus senegalensis and Maytenus undata were evaluated for antimicrobial, anti-inflammatory and antioxidant activities to determine their efficacy as therapeutic agents in GIT disorders.

METHODS

Phenolic-enriched leaf extracts and fractions were prepared by extracting with acidified 70% methanol and solvent-solvent fractionation. The activities of the fractions against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Enterococcus faecalis as well as clinical isolates of Aspergillus fumigatus, Candida albicans and Cryptococcus neoformans were determined using a serial microplate dilution method. Antioxidant activities were determined using 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azinobis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS), hydroxyl (OH) radical scavenging and linoleic acid peroxidation inhibitory assays. The phenolic composition as well as the cytotoxicity against Vero cell lines of the crude extracts was evaluated using various standard protocols.

RESULTS

The antimicrobial activities were concentrated in the non-polar fractions of hexane, dichloromethane and ethyl acetate (MICs 19-312 μg/ml). The crude extracts and polar fractions (butanol and water) had moderate to poor antimicrobial activity (MICs 312 to above 2500 μg/ml). The crude extracts and polar fractions had good antioxidant activity (EC50 values varied from 1.22 to 607 μg/ml, 1.71 to 312 μg/ml and 23 to 284 μg/ml for DPPH, ABTS and OH respectively. Linoleic acid peroxidation inhibition EC50 values of the crude extracts ranged between 27 and 39 μg/ml with relatively low toxicity against Vero cell lines (IC50 values 87 to 187 μg/ml). Fractionation of a crude extract with low activity could lead to fractions with more potent activity.

CONCLUSION

This study justifies the traditional use of leaf crude extracts and fractions from these four plants to remedy gastrointestinal disorders resulting from infection, inflammation and oxidative stress complications. The study also provides rationale for the use of leaf extracts with same beneficial effects in place of unsustainable root and bark harvest.

Optimization of a small intestinal segment perfusion model for heat-stable enterotoxin A induced secretion in pigs

Enterotoxigenic Escherichia coli (ETEC) are a major cause of infectious diarrhea both in human and pigs. After ingestion of contaminated food or water, ETEC bacteria colonize the small intestine where they produce heat-labile (LT) and/or heat-stable (ST) enterotoxins, which induce watery diarrhea. We investigated the possibility of eliciting STa-induced secretion in jejunal segments of anesthetized pigs using a small-intestinal segment perfusion (SISP) model. Five consecutive mid-jejunal segments of anaesthetized piglets were perfused for 6h with different concentrations of STa in a physiologic salt solution. Changes in intestinal net fluid absorption were measured. From the results we could conclude that the STa response was dose-dependent and that continuous perfusion with 50 nM of STa or more was required to reduce net absorption. This concentration was sufficient to reduce net absorption compared to control segments in 12 out of 14 piglets. STa-induced responses however showed relative high variation between different jejunal segments of one pig, similar to the inter-segment variation seen in control animals where segments were perfused with physiologic salt solution. These results indicate that more optimization is required before this model could be used to test compounds that could interfere with the STa-induced fluid secretion.

Small intestinal segment perfusion test in piglets: future applications in studying probiotics-gut crosstalk in infectious diarrhoea?

Worldwide infectious diarrhoea, mainly caused by rotavirus and enterotoxigenic Escherichia coli (ETEC), accounts for a large part of deaths in children. ETEC is also the main cause of traveller's diarrhoea. Probiotics are promising for prevention and treatment of diarrhoea, but there is insufficient evidence to support the use of any specific probiotic or probiotics in general. Because of the sensitivity of suckling and weaned piglets for ETEC, piglets are a good model for infectious diarrhoea in infants and traveller's diarrhoea. Just as in human the efficacy of probiotics in diminishing diarrhoea and improving growth in suckling and weaned piglets is not uniform. A piglet model of infectious diarrhoea provides access to intestinal compartments that are not easily accessible in infants. In an in situ piglet model of secretory diarrhoea, the functional physiological response to ETEC and the concomitant host genome response to ETEC and probiotics may be tested. This will provide new insights in the complex crosstalk between ETEC, probiotics and the gut in the future.

Effect of products derived from hydrolysis of wheat and flaxseed non starch polysaccharides by carbohydrase enzymes on net absorption in enterotoxigenic Escherichia coli (K88) challenged piglet jejunal segments

Enterotoxigenic Escherichia coli (ETEC) infection results in fluid and electrolyte losses in the small intestine. We investigated the effect of non-starch polysaccharides (NSP) hydrolysis products of wheat middlings (WM) and flaxseed (FS) on net absorption of fluid and solutes during ETEC challenge. Products were generated by incubating WM and FS with a blend of carbohydrase enzymes to produce 2 products: 80% ethanol-soluble (ES) and 80% ethanol-insoluble (EI) which were studied in 2 experiments in which 2 factors were investigated: products (EI vs. ES) and time of ETEC challenge (before vs. after perfusion). Pairs of small-intestine segments, one non-challenged and the other ETEC-challenged were perfused with products for 7.5 h. ETEC reduced fluid absorption by more than 380 microL/cm(2) in saline (control) perfused segments, whereas this reduction was significantly (P < 0.05) less for the WM and FS products. Interaction (P > 0.05) between product and time of challenge was not observed. For WM, products effects on ETEC-challenged segments were such that perfusion of ES resulted in higher total solute (measured as osmolality) absorption than EI (138 vs. 103 microOsmol/cm(2)). In conclusion, hydrolysis products from WM and FS were beneficial in maintaining fluid balance during ETEC challenge, suggesting potential in controlling ETEC induced diarrhea in piglets.

Identification of Escherichia coli enterotoxin inhibitors from traditional medicinal herbs by in silico, in vitro, and in vivo analyses

ETHNOPHARMACOLOGICAL RELEVANCE

Glycyrrhiza uralensis has been used for the treatment of gastrointestinal disorders, such as diarrhea, in several ancient cultures. Glycyrrhizin is the principal component of liquorice and lots of pharmacological effects have been demonstrated.

AIM OF THE STUDY

Heat-labile enterotoxin (LT), the virulence factor of enterotoxigenic Escherichia coli, induces diarrhea by initially binding to the GM1 on the surfaces of intestinal epithelial cells and consequently leading to the massive loss of fluid and ions from cells. Therefore, we evaluated the inhibitory effects of traditional medicinal herbs (TMH) on the B subunit of LT (LTB) and GM1 interaction.

MATERIALS AND METHODS

The inhibitory effects of TMH on LTB-GM1 interaction were evaluated by GM1-enzyme-linked immunosorbent assay (ELISA). The likely active phytochemicals of these TMH were then predicted by in silico model (docking) and analyzed by in vitro (GM1-ELISA) and in vivo (patent mouse gut assay) models.

RESULTS

We found that various TMH, which have been ethnomedically used for the treatment of diarrhea, inhibited the LTB-GM1 interaction. Docking data showed that triterpenoids were the most active phytochemicals and the oleanane-type triterpenoids presented better LTB-binding abilities than other types of triterpenoids. Moreover, by in vitro and in vivo models, we demonstrated that glycyrrhizin was the most effective oleanane-type triterpenoid that significantly suppressed both the LTB-binding ability (IC50=3.26+/-0.17 mM) and the LT-induced fluid accumulation in mice.

CONCLUSIONS

We found an LT inhibitor, glycyrrhizin, from TMH by in silico, in vitro, and in vivo analyses.

Mannose-specific interaction of Lactobacillus plantarum with porcine jejunal epithelium

Host-microorganism interactions in the intestinal tract are complex, and little is known about specific nonpathogenic microbial factors triggering host responses in the gut. In this study, mannose-specific interactions of Lactobacillus plantarum 299v with jejunal epithelium were investigated using an in situ pig Small Intestinal Segment Perfusion model. The effects of L. plantarum 299v wild-type strain were compared with those of two corresponding mutant strains either lacking the gene encoding for the mannose-specific adhesin (msa) or sortase (srtA; responsible for anchoring of cell surface proteins like Msa to the cell wall). A slight enrichment of the wild-type strain associated with the intestinal surface could be observed after 8 h of perfusion when a mixture of wild-type and msa-mutant strain had been applied. In contrast to the mutant strains, the L. plantarum wild-type strain tended to induce a decrease in jejunal net fluid absorption compared with control conditions. Furthermore, after 8 h of perfusion expression of the host gene encoding pancreatitis-associated protein, a protein with proposed bactericidal properties, was found to be upregulated by the wild-type strain only. These observations suggest a role of Msa in the induction of host responses in the pig intestine.

Nonstarch polysaccharide hydrolysis products of soybean and canola meal protect against enterotoxigenic Escherichia coli in piglets

Infectious diarrhea is a major problem in both children and piglets. Enterotoxigenic Escherichia coli (ETEC) infection results in fluid and electrolyte losses in the small intestine. We investigated the effect of nonstarch polysaccharide (NSP) hydrolysis products of soybean meal (SBM) and canola meal (CM) on net absorption of fluid and solutes during ETEC infection. Products were generated by incubating SBM and CM with a blend of carbohydrase enzymes. Following incubation, slurries were centrifuged and the supernatants mixed with absolute ethanol to produce 2 product types: 80% ethanol-soluble (ES) and 80% ethanol-insoluble (EI). Products from SBM and CM were studied in 2 independent experiments in which 2 factors were investigated: product type (EI vs. ES) and time of ETEC infection (before vs. after perfusion). Pairs of small intestine segments, one noninfected and the other ETEC infected, were perfused simultaneously with different products for 7.5 h. Net absorption of fluid and solutes were determined. In both experiments, ETEC-infected segments perfused with saline control had lower (P < or = 0.05) net fluid and solute absorption compared with SBM and CM products. The interaction (P < or = 0.05) between product type and time of infection on fluid absorption was only evident for SBM, in which case perfusing ES products before infection resulted in higher fluid absorption (735 +/- 22 microL/cm2) compared with ETEC infection before perfusion (428 +/- 34 microL/cm2). In conclusion, NSP hydrolysis products of SBM and CM, particularly ES from SBM, were beneficial in maintaining fluid balance during ETEC infection, suggesting potential for controlling ETEC-induced diarrhea in piglets.

Ginger and its bioactive component inhibit enterotoxigenic Escherichia coli heat-labile enterotoxin-induced diarrhea in mice

Ginger is one of the most commonly used fresh herbs and spices. Enterotoxigenic Escherichia coli heat-labile enterotoxin (LT)-induced diarrhea is the leading cause of infant death in developing countries. In this study, we demonstrated that ginger significantly blocked the binding of LT to cell-surface receptor G M1, resulting in the inhibition of fluid accumulation in the closed ileal loops of mice. Biological-activity-guided searching for active components showed that zingerone (vanillylacetone) was the likely active constituent responsible for the antidiarrheal efficacy of ginger. Further analysis of chemically synthesized zingerone derivatives revealed that compound 31 (2-[(4-methoxybenzyl)oxy]benzoic acid) significantly suppressed LT-induced diarrhea in mice via an excellent surface complementarity with the B subunits of LT. In conclusion, our findings provide evidence that ginger and its derivatives may be effective herbal supplements for the clinical treatment of enterotoxigenic Escherichia coli diarrhea.