Probiotics inhibit enteropathogenic E. coli adherence in vitro by inducing intestinal mucin gene expression

Impact of a probiotic fermented milk in the gut ecosystem and in the systemic immunity using a non-severe protein-energy-malnutrition model in mice

BACKGROUND

Malnutrition affects the immune response, causing a decrease of defence mechanisms and making the host more susceptible to infections. Probiotics can reconstitute the intestinal mucosa and stimulate local and systemic immunity. The aim of this work was evaluate the effects of a probiotic fermented milk as a complement of a re-nutrition diet, on the recovery of the intestinal barrier, and mucosal and systemic immune functions in a murine model of non-severe protein-energy-malnutrition. Its potential protection against Salmonella enterica serovar Typhimurium (S. Typhimurium) infection was also analyzed.

METHODS

Mice were undernourished and divided into 3 groups according to the dietary supplement received during re-nutrition (milk, probiotic fermented milk or its bacterial free supernatant) and compared to well-nourished and malnourished mice. They were sacrificed previous to the re-nutrition and 5 days post re-nutrition. The phagocytic activity of macrophages from spleen and peritoneum and the changes in the intestinal histology and microbiota were evaluated. Different immune cell populations and cytokine productions were analyzed in the small intestine tissues. The effect of the re-nutrition supplements on the systemic immunity using OVA antigen and against an infection with S. Typhimurium was also studied.

RESULTS

Probiotic fermented milk was the most effective re-nutrition diet that improved the intestinal microbiota. Its administration also increased the number of IgA+ cells, macrophages and dendritic cells. The production of different cytokine (IFN-γ, TNF-α, IL-12) by these cells and the phagocytic activity in peritoneum and spleen was also increased. This re-nutrition diet also stimulated the systemic immune response against OVA antigen which was diminished after the malnutrition period and also improved the host response against S. Typhimurium, decreasing the spread of pathogenic bacteria to the liver and the spleen. The importance of the metabolites released during milk fermentation was also demonstrated through the analysis of the bacterial free supernatant obtained from the probiotic fermented milk, but the whole product showed the best effects in the parameters evaluated in this study.

CONCLUSIONS

The administration of probiotic fermented milk as a dietary supplement during the re-nutrition process in a murine immunodeficiency model by malnutrition could be a good adjuvant diet to improve the gut and systemic immune response for the protection against Salmonella infection.

Probiotics in the prevention of antibiotic-associated diarrhoea and Clostridium difficile infection

Diarrhoea, as a common side effect of antibiotics, increases treatment costs and length of stay in acute healthcare facilities. One potential strategy to prevent this side effect is the concurrent use of probiotic bacteria or yeast. This review discusses the evidence for the efficacy of probiotics in the prevention of antibiotic-associated diarrhoea and Clostridium difficile infection; the potential mechanisms by which probiotics may work; their safety; what future research is required; and recommendations for use in clinical practice.

A prebiotic, Celmanax™, decreases Escherichia coli O157:H7 colonization of bovine cells and feed-associated cytotoxicity in vitro

Background

Escherichia coli O157:H7 is the most common serovar of enterohemorrhagic E. coli associated with serious human disease outbreaks. Cattle are the main reservoir with E. coli O157:H7 inducing hemorrhagic enteritis in persistent shedding beef cattle, however little is known about how this pathogen affects cattle health. Jejunal Hemorrhage Syndrome (JHS) has unclear etiology but the pathology is similar to that described for E. coli O157:H7 challenged beef cattle suggestive that E. coli O157:H7 could be involved. There are no effective treatments for JHS however new approaches to managing pathogen issues in livestock using prebiotics and probiotics are gaining support. The first objective of the current study was to characterize pathogen colonization in hemorrhaged jejunum of dairy cattle during natural JHS outbreaks. The second objective was to confirm the association of mycotoxigenic fungi in feeds with the development of JHS and also to identify the presence of potential mycotoxins. The third objective was to determine the impact of a prebiotic, Celmanax™, or probiotic, Dairyman's Choice™ paste, on the cytotoxicity associated with feed extracts in vitro. The fourth objective was to determine the impact of a prebiotic or a probiotic on E. coli O157:H7 colonization of mucosal explants and a bovine colonic cell line in vitro. The final objective was to determine if prebiotic and probiotic feed additives could modify the symptoms that preceded JHS losses and the development of new JHS cases.

Findings

Dairy cattle developed JHS after consuming feed containing several types of mycotoxigenic fungi including Fusarium culmorum, F. poae, F. verticillioides, F. sporotrichioides, Aspergillusflavus, Penicillium roqueforti, P. crustosum, P. paneum and P. citrinum. Mixtures of Shiga toxin - producing Escherichia coli (STEC) colonized the mucosa in the hemorrhaged tissues of the cattle and no other pathogen was identified. The STECs expressed Stx1 and Stx2, but more significantly, Stxs were also present in the blood clot blocking the jejunum. Mycotoxin analysis of the corn crop confirmed the presence of fumonisin, NIV, ZEAR, DON, 15-ADON, 3-ADON, NEO, DAS, HT-2 and T-2. Feed extracts were toxic to enterocytes and 0.1% Celmanax™ removed the cytotoxicity in vitro. There was no effect of Dairyman's Choice™ paste on feed-extract activity in vitro. Fumonisin, T-2, ZEAR and DON were toxic to bovine cells and 0.1% Celmanax™ removed the cytotoxicity in vitro. Celmanax™ also directly decreased E. coli O157:H7 colonization of mucosal explants and a colonic cell line in a dose-dependent manner. There was no effect of Dairyman's Choice™ paste on E. coli O157:H7 colonization in vitro. The inclusion of the prebiotic and probiotic in the feed was associated with a decline in disease.

Conclusion

The current study confirmed an association between mycotoxigenic fungi in the feed and the development of JHS in cattle. This association was further expanded to include mycotoxins in the feed and mixtures of STECs colonizing the severely hemorrhaged tissues. Future studies should examine the extent of involvement of the different STEC in the infection process. The prebiotic, Celmanax™, acted as an anti-adhesive for STEC colonization and a mycotoxin binder in vitro. Future studies should determine the extent of involvement of the prebiotic in altering disease.

Gut microbiota is not modified by Randomized, Double-blind, Placebo-controlled Trial of VSL#3 in Diarrhea-predominant Irritable Bowel Syndrome

Irritable Bowel Syndrome (IBS) is a common condition that negatively impacts the quality of life for many individuals. The exact etiology of this disorder is largely unknown; however, emerging studies suggest that the gut microbiota is a contributing factor. Several clinical trials show that probiotics, such as VSL#3, can have a favorable effect on IBS. This double-blind, randomized placebo-controlled study has been conducted in diarrhea-predominant IBS subjects in order to investigate the effect of VSL#3 on the fecal microbiota. The bacterial composition of the fecal microbiota was investigated using high-throughput microarray technology to detect 16S RNA. Twenty four subjects were randomized to receive VSL#3 or placebo for 8 weeks. IBS symptoms were monitored using GSRS and quality of life questionnaires. A favorable change in Satiety subscale was noted in the VSL #3 groups. However, the consumption of the probiotic did not change the gut microbiota. There were no adverse events or any safety concerns encountered during this study. To summarize, the use of VSL#3 in this pilot study was safe and showed improvement in specific GSRS-IBS scores in diarrhea-predominant IBS subjects. The gut microbiota was not affected by VSL#3 consumption suggesting that the mechanism of action is not directly linked to the microbiota.

Antibiotic treatment alters the colonic mucus layer and predisposes the host to exacerbated Citrobacter rodentium-induced colitis

Antibiotics are often used in the clinic to treat bacterial infections, but the effects of these drugs on microbiota composition and on intestinal immunity are poorly understood. Citrobacter rodentium was used as a model enteric pathogen to investigate the effect of microbial perturbation on intestinal barriers and susceptibility to colitis. Streptomycin and metronidazole were used to induce alterations in the composition of the microbiota prior to infection with C. rodentium. Metronidazole pretreatment increased susceptibility to C. rodentium-induced colitis over that of untreated and streptomycin-pretreated mice, 6 days postinfection. Both antibiotic treatments altered microbial composition, without affecting total numbers, but metronidazole treatment resulted in a more dramatic change, including a reduced population of Porphyromonadaceae and increased numbers of lactobacilli. Disruption of the microbiota with metronidazole, but not streptomycin treatment, resulted in an increased inflammatory tone of the intestine characterized by increased bacterial stimulation of the epithelium, altered goblet cell function, and thinning of the inner mucus layer, suggesting a weakened mucosal barrier. This reduction in mucus thickness correlates with increased attachment of C. rodentium to the intestinal epithelium, contributing to the exacerbated severity of C. rodentium-induced colitis in metronidazole-pretreated mice. These results suggest that antibiotic perturbation of the microbiota can disrupt intestinal homeostasis and the integrity of intestinal defenses, which protect against invading pathogens and intestinal inflammation.

Intestinal goblet cells and mucins in health and disease: recent insights and progress

The mucus layer coating the gastrointestinal tract is the front line of innate host defense, largely because of the secretory products of intestinal goblet cells. Goblet cells synthesize secretory mucin glycoproteins (MUC2) and bioactive molecules such as epithelial membrane-bound mucins (MUC1, MUC3, MUC17), trefoil factor peptides (TFF), resistin-like molecule beta (RELMbeta), and Fc-gamma binding protein (Fcgbp). The MUC2 mucin protein forms trimers by disulfide bonding in cysteine-rich amino terminal von Willebrand factor (vWF) domains, coupled with crosslinking provided by TFF and Fcgbp proteins with MUC2 vWF domains, resulting in a highly viscous extracellular layer. Colonization by commensal intestinal microbiota is limited to an outer "loose" mucus layer, and interacts with the diverse oligosaccharides of mucin glycoproteins, whereas an "inner" adherent mucus layer is largely devoid of bacteria. Defective mucus layers resulting from lack of MUC2 mucin, mutated Muc2 mucin vWF domains, or from deletion of core mucin glycosyltransferase enzymes in mice result in increased bacterial adhesion to the surface epithelium, increased intestinal permeability, and enhanced susceptibility to colitis caused by dextran sodium sulfate. Changes in mucin gene expression and mucin glycan structures occur in cancers of the intestine, contributing to diverse biologic properties involved in the development and progression of cancer. Further research is needed on identification and functional significance of various components of mucus layers and the complex interactions among mucus layers, microbiota, epithelial cells, and the underlying innate and adaptive immunity. Further elucidation of the regulatory mechanisms involved in mucin changes in cancer and inflammation may lead to the development of novel therapeutic approaches.

Effect of lactobacilli on paracellular permeability in the gut

Paracellular permeability is determined by the complex structures of junctions that are located between the epithelial cells. Already in 1996, it was shown that the human probiotic strain Lactobacillus plantarum 299v and the rat-originating strain Lactobacillus reuteri R2LC could reduce this permeability in a methotrexate-induced colitis model in the rat. Subsequently, many animal models and cell culture systems have shown indications that lactobacilli are able to counteract increased paracellular permeability evoked by cytokines, chemicals, infections, or stress. There have been few human studies focusing on the effect of lactobacilli on intestinal paracellular permeability but recently it has been shown that they could influence the tight junctions. More precisely, short-term administration of L. plantarum WCSF1 to healthy volunteers increased the relocation of occludin and ZO-1 into the tight junction area between duodenal epithelial cells.

Characterisation and response of intestinal microflora and mucins to manno-oligosaccharide and antibiotic supplementation in broiler chickens

1. An experiment was conducted to characterise and evaluate, in comparison to zinc bacitracin (ZnB), the response of intestinal microflora and mucins to manno-oligosacchares (MOS, Bio-MOS(R), Alltech Biotechnology, Nicholasville, Kentucky, USA). 2. Supplementation of MOS and ZnB selectively increased the intensity of sulphomucins. As revealed by the plate culture method, MOS accelerated the maturation of gut microflora by promoting the growth of lactobacilli in the ileal mucosa and vice versa on ileal and caecal clostridia. Unlike MOS, ZnB suppressed the growth of intestinal bacteria, especially those of lactobacilli and clostridia. Use of T-RFLP further revealed that MOS increased the diversity of lactobacilli in the ileum and ileal mucosa but the opposite was observed for ZnB. It also appears that MOS and ZnB possessed a common property in differentially favouring the growth of certain Lactobacillus species. There was also evidence to show that both MOS and ZnB also increased the homogeneity of the gut microflora, possibly through the regulation of the overall gut bacterial communities. 3. Improvement in intestinal microbial homogeneity and mucin synthesis, coupled with the differential selections for certain specific beneficial bacterial species, may ultimately be proven to be the target mechanisms in the search for more effective alternatives to antibiotics.

Interaction of orally administered Lactobacillus rhamnosus GG with skin and gut microbiota and humoral immunity in infants with atopic dermatitis

BACKGROUND

The intestinal mucosa functions as a defence barrier against gut intraluminar antigens. The maturational events in the gut parallel its step-wise colonization. Atopic dermatitis (AD) is associated with aberrant barrier functions of the skin epithelium and, in a subgroup of patients, of the gut mucosa.

OBJECTIVE

To investigate the interaction of Lactobacillus rhamnosus GG (LGG) with skin and gut microbiota and humoral immunity in infants with AD.

METHODS

Thirty-nine infants with AD were randomized for a 3-month period in a double-blind design to receive extensively hydrolysed casein formula supplemented with (n=19) or without (n=20) LGG (ATCC 53103) 5.0 × 10⁷ CFU/g to achieve a daily intake of 3.4 × 10⁹ CFU. Sampling (blood and fecal samples, cotton swab from the skin) was carried out at entry, 1 and 3 months thereafter. Ig-secreting cells were determined by enzyme-linked immunospot and the proportions of CD19(+)CD27(+) B cells among peripheral blood leucocytes by flow cytometry. The major groups of gut and skin bacteria were characterized using PCR.

RESULTS

The proportions of IgA- and IgM-secreting cells decreased significantly in the treated group; the baseline-adjusted ratios for treated vs. untreated at 1 month were 0.59 (95%CI 0.36-0.99, P=0.044) for IgA- and 0.53 (95%CI 0.29-0.96, P=0.036) for IgM-secreting cells. The proportions of CD19(+)CD27(+) B cells increased in the probiotic-treated infants but not in the untreated. There were no significant differences in bifidobacterial species composition of the gut between the study groups. On the skin, the bacterial counts of Bifidobacterium genus vs. Clostridium coccoides in the treated and untreated infants were similar.

CONCLUSION AND CLINICAL RELEVANCE

Specific probiotics may enhance gut barrier function and aid in the development of immune responses. Thus, specific probiotics may afford protection against offending macromolecules in the gut and provide control for future infections by accelerated immunological maturation (ClinicalTrials.gov ID NCT01148667).

Effects of Lactobacillus rhamnosus GG on saliva-derived microcosms

OBJECTIVE

The probiotic strain Lactobacillus rhamnosus GG (LGG) is shown to hamper the presence of mutans streptococci in saliva and may have positive effects on oral health. We investigated the effects of LGG on the cariogenic potential and microbial composition of saliva-derived microcosms.

DESIGN

Single and dual species biofilms of LGG and Streptococcus mutans, and saliva-derived microcosms with or without LGG were grown in an Active Attachment Biofilm model. The microcosms were grown on bovine dentin/enamel discs in the presence or absence of sucrose (suc+/suc-). The presence of LGG was determined by multiplex ligation-dependent probe amplification (MLPA) and real-time PCR. Mutans streptococci (MS) and total viable counts, pH of the spent medium, capacity of lactate formation and integrated mineral loss in dentin was assessed. MLPA was used for identification and relative quantification of 20 oral microorganisms in the microcosms. Principal Component Analysis was applied to MLPA data.

RESULTS

LGG inhibited the growth of S. mutans in dual species biofilms and did not affect the pH. LGG established in saliva-derived microcosms and reduced MS counts significantly, but did not affect pH or dentin demineralization. Simultaneous growth of the microcosms with LGG under heavy cariogenic conditions (suc+) introduced a compositional shift in the microbial community. The CFU, real-time PCR and MLPA data correlated significantly.

CONCLUSION

We conclude that LGG established into and inhibited the growth of MS in complex saliva-derived biofilms, but this had no significant effect on cariogenic potential of the microcosms. This suggests that other microorganisms besides MS were responsible for increased cariogenicity of sucrose-exposed biofilms.

Porcine small intestinal epithelial cell line (IPEC-J2) of rotavirus infection as a new model for the study of innate immune responses to rotaviruses and probiotics

Previous studies of epithelial immune responses to rotavirus infection have been conducted in transformed cell lines. In this study, we evaluated a non-transformed porcine jejunum epithelial cell line (IPEC-J2) as an in-vitro model of rotavirus infection and probiotic treatment. Cell-culture-adapted porcine rotavirus (PRV) OSU strain, or human rotavirus (HRV) Wa strain, along with Lactobacillus acidophilus (LA) or Lactobacillus rhamnosus GG (LGG) were used to inoculate IPEC-J2 cells. LA or LGG treatment was applied pre- or post-rotavirus infection. We demonstrated that IPEC-J2 cells were productively infected by PRV. LA or LGG treatment of the cells did not reduce virus replication. PRV infection increased MUC3 mucin secretion. LGG treatment post-rotavirus infection reduced the mucin secretion response induced by PRV; LGG alone increased the production of membrane-associated MUC3 mucin. LA treatment prior to rotavirus infection significantly increased PRV replication and the IL-6 response to PRV infection, which is consistent with the adjuvant effect of LA. LGG treatment post-rotavirus infection downregulated the IL-6 response, confirming the anti-inflammatory effect of LGG. IPEC-J2 cells expressed toll-like receptor (TLR) 2, TLR3, and TLR9 constitutively. TLR2 expression was upregulated by LGG and peptidoglycan, corresponding to the decreased IL-6 response, indicating that the protective effect of LGG is associated with upregulation of TLR2 expression on intestinal epithelial cells. The IPEC-J2 cell model of PRV infection is a completely homologous system. It is a valuable model for studying the interactions among rotavirus-host-probiotics, and the mechanisms behind the immunomodulating effect of probiotic bacteria on innate immune responses.

Dietary supplementation with a probiotic fermented four-herb combination enhances immune activity in broiler chicks and increases survivability against Salmonella Gallinarum in experimentally infected broiler chicks

Herbs including Curcuma longa, Houttuynia cordata, Prunus mume and Rubus coreanus have potential immune enhancing and antimicrobial effects. Probiotics also have antibacterial effects, and some are important in regulating the immune system. The aims of the present study were to evaluate the immune enhancing effects of a probiotic fermented four-herb combination (PFH) in broiler chicks and to demonstrate the prophylactic effect of PFH against Salmonella Gallinarum in experimentally infected broiler chicks as an initial step towards the development of feed supplements for promotion of immune activity and disease prevention. Continuous ingestion of PFH markedly increased lysozyme activity in serum and the spleen, peripheral blood mononuclear cell (PBMC) proliferation, the CD4(+):CD8(+) T lymphocyte ratio in the spleen and antibody production level in broiler chicks. Conversely, prostaglandin E(2) synthesis in serum and PBMC culture medium was significantly decreased in the PFH-fed chicks compared with the control group in a dose-dependent manner. In the chicks experimentally infected with S. Gallinarum, mortality was delayed in the 2% PFH-fed chicks. Moreover, the survival rates in the 2% PFH-fed group remained the highest among all the trial groups throughout the experimental period. Taken together, these findings suggest that PFH enhances immune activity in broiler chicks and increases survivability against Salmonella Gallinarum in experimentally infected broiler chicks, likely because of potent stimulation of nonspecific immune responses.

Back to the future: studying cholera pathogenesis using infant rabbits

Cholera is a severe diarrheal disease, caused by Vibrio cholerae, for which there has been no reproducible, nonsurgical animal model. Here, we report that orogastric inoculation of V. cholerae into 3-day-old rabbits pretreated with cimetidine led to lethal, watery diarrhea in virtually all rabbits. The appearance and chemical composition of the rabbit diarrheal fluid were comparable to those of the “rice-water stool” produced by cholera patients. As in humans, V. cholerae mutants that do not produce cholera toxin (CT) and toxin-coregulated pilus (TCP) did not induce cholera-like disease in rabbits. CT induced extensive exocytosis of mucin from intestinal goblet cells, and wild-type V. cholerae was predominantly found in close association with mucin. Large aggregates of mucin-embedded V. cholerae were observed, both attached to the epithelium and floating within the diarrheal fluid. These findings suggest that CT-dependent mucin secretion significantly influences V. cholerae’s association with the host intestine and its exit from the intestinal tract. Our model should facilitate identification and analyses of factors that may govern V. cholerae infection, survival, and transmission, such as mucin. In addition, our results using nontoxigenic V. cholerae suggest that infant rabbits will be useful for study of the reactogenicity of live attenuated-V. cholerae vaccines.

Cholera remains a significant threat to populations in developing nations. Currently, there is no reproducible, nonsurgical animal model of cholera, the secretory diarrheal disease caused by Vibrio cholerae. We found that oral infection of infant rabbits with V. cholerae led to lethal, watery diarrhea in most rabbits. Using this disease model, we discovered a new role for cholera toxin (CT) during infection. This toxin not only caused secretory diarrhea but also profoundly influenced how V. cholerae associates with the intestine and how the pathogen exits from the host. Rabbits inoculated with V. cholerae that does not produce CT developed mild diarrhea, suggesting that this model may prove useful for generating improved live attenuated-V. cholerae vaccine candidates. Overall, our findings suggest that the infant rabbit model will enable pursuit of several new avenues for research on cholera pathogenesis, as well as serve as a vehicle for testing new therapeutics.

Muc2 protects against lethal infectious colitis by disassociating pathogenic and commensal bacteria from the colonic mucosa

Despite recent advances in our understanding of the pathogenesis of attaching and effacing (A/E) Escherichia coli infections, the mechanisms by which the host defends against these microbes are unclear. The goal of this study was to determine the role of goblet cell-derived Muc2, the major intestinal secretory mucin and primary component of the mucus layer, in host protection against A/E pathogens. To assess the role of Muc2 during A/E bacterial infections, we inoculated Muc2 deficient (Muc2^−/−) mice with Citrobacter rodentium, a murine A/E pathogen related to diarrheagenic A/E E. coli. Unlike wildtype (WT) mice, infected Muc2^−/− mice exhibited rapid weight loss and suffered up to 90% mortality. Stool plating demonstrated 10–100 fold greater C. rodentium burdens in Muc2^−/− vs. WT mice, most of which were found to be loosely adherent to the colonic mucosa. Histology of Muc2^−/− mice revealed ulceration in the colon amid focal bacterial microcolonies. Metabolic labeling of secreted mucins in the large intestine demonstrated that mucin secretion was markedly increased in WT mice during infection compared to uninfected controls, suggesting that the host uses increased mucin release to flush pathogens from the mucosal surface. Muc2 also impacted host-commensal interactions during infection, as FISH analysis revealed C. rodentium microcolonies contained numerous commensal microbes, which was not observed in WT mice. Orally administered FITC-Dextran and FISH staining showed significantly worsened intestinal barrier disruption in Muc2^−/− vs. WT mice, with overt pathogen and commensal translocation into the Muc2^−/− colonic mucosa. Interestingly, commensal depletion enhanced C. rodentium colonization of Muc2^−/− mice, although colonic pathology was not significantly altered. In conclusion, Muc2 production is critical for host protection during A/E bacterial infections, by limiting overall pathogen and commensal numbers associated with the colonic mucosal surface. Such actions limit tissue damage and translocation of pathogenic and commensal bacteria across the epithelium.

Enteropathogenic E. coli (EPEC) and Enterohemorrhagic E. coli (EHEC) are important causes of diarrheal disease and other serious complications worldwide. Despite many studies addressing the pathogenic strategies used by these microbes, how the host protects itself from these pathogens is poorly understood. A critical question we address here is whether the thick mucus layer that overlies the intestinal surface plays a role in host protection. Since EPEC and EHEC do not infect mice efficiently, we used a related mouse pathogen called Citrobacter rodentium to infect and compare responses between wildtype mice and Muc2-deficient mice, which are defective in mucus production. We show that Muc2-deficient mice are extremely susceptible to C. rodentium infection-induced mortality and disease. Muc2-deficient mice were also colonized faster and had higher pathogen burdens throughout the experiment. Resident (non-pathogenic) bacteria were found to interact with C. rodentium and host tissues in Muc2-deficient mice, indicating Muc2 regulates all forms of intestinal microbiota at the gut surface. Deficiency in mucus production also contributed to increased leakiness of the gut, which allowed microbes to enter mucosal tissues. Our study shows that Muc2-dependent mucus production is critical for effective management of both pathogenic and non-pathogenic bacteria during infection by an EPEC/EHEC-like pathogen.

Lactobacillus johnsonii N6.2 mitigates the development of type 1 diabetes in BB-DP rats

Background

The intestinal epithelium is a barrier that composes one of the most immunologically active surfaces of the body due to constant exposure to microorganisms as well as an infinite diversity of food antigens. Disruption of intestinal barrier function and aberrant mucosal immune activation have been implicated in a variety of diseases within and outside of the gastrointestinal tract. With this model in mind, recent studies have shown a link between diet, composition of intestinal microbiota, and type 1 diabetes pathogenesis. In the BioBreeding rat model of type 1 diabetes, comparison of the intestinal microbial composition of diabetes prone and diabetes resistant animals found Lactobacillus species were negatively correlated with type 1 diabetes development. Two species, Lactobacillus johnsonii and L. reuteri, were isolated from diabetes resistant rats. In this study diabetes prone rats were administered pure cultures of L. johnsonii or L. reuteri isolated from diabetes resistant rats to determine the effect on type 1 diabetes development.

Methodology/Principal

Findings Results Rats administered L. johnsonii, but not L. reuteri, post-weaning developed type 1 diabetes at a protracted rate. Analysis of the intestinal ileum showed administration of L. johnsonii induced changes in the native microbiota, host mucosal proteins, and host oxidative stress response. A decreased oxidative intestinal environment was evidenced by decreased expression of several oxidative response proteins in the intestinal mucosa (Gpx1, GR, Cat). In L. johnsonii fed animals low levels of the pro-inflammatory cytokine IFNγ were correlated with low levels of iNOS and high levels of Cox2. The administration of L. johnsonii also resulted in higher levels of the tight junction protein claudin.

Conclusions

It was determined that the administration of L. johnsonii isolated from BioBreeding diabetes resistant rats delays or inhibits the onset of type 1 diabetes in BioBreeding diabetes prone rats. Taken collectively, these data suggest that the gut and the gut microbiota are potential agents of influence in type 1 diabetes development. These data also support therapeutic efforts that seek to modify gut microbiota as a means to modulate development of this disorder.

Immune-enhancing effect of fermented Maesil (Prunus mume Siebold & Zucc.) with probiotics against Bordetella bronchiseptica in mice

Maesil (Prunus mume) has long been used as a traditional drug and healthy food in East Asian countries. It possesses a number of beneficial biological activities including potential antimicrobial effects against pathogens. Probiotics also have antibacterial effects. Moreover, some probiotics have an important role in regulating the immune system. The present study evaluated the immune enhancing effects of fermented Maesil with probiotics (Saccharomyces cerevisiae, Bacillus subtilis and Lactobacillus acidophilus) in mice, especially against Bordetella bronchiseptica, as an initial step towards the development of feed supplements for the promotion of immune activity and prevention of disease, especially in pigs. Continuous ingestion of fermented Maesil with probiotics markedly increased the macrophage ratio in peripheral blood and the T lymphocyte ratio in the spleen. In addition, antibody production against formalin-killed B. bronchiseptica significantly increased in the mice fed fermented Maesil compared with the control group. The number of leukocytes was significantly higher in the bronchio-alveolar lavage obtained from the fermented Maesil-fed animals compared to it in the control group at day 3 (maximal peak time) after experimental B. bronchiseptica infection. Moreover, at 7 day post-infection, relative messenger RNA expression levels of tumor necrosis factor- α and interferon-γ were significantly increased in splenocytes of mice fed fermented Maesil compared with those in the control group. Taken together, these findings suggest that feed containing fermented Maesil with probiotics enhances immune activity in mice, especially against B. bronchiseptica, via the potent stimulation of non-specific immune responses.

Two atypical enteropathogenic Escherichia coli strains induce the production of secreted and membrane-bound mucins to benefit their own growth at the apical surface of human mucin-secreting intestinal HT29-MTX cells

In rabbit ligated ileal loops, two atypical enteropathogenic Escherichia coli (aEPEC) strains, 3991-1 and 0421-1, intimately associated with the cell membrane, forming the characteristic EPEC attachment and effacement lesion of the brush border, induced a mucous hypersecretion, whereas typical EPEC (tEPEC) strain E2348/69 did not. Using cultured human mucin-secreting intestinal HT29-MTX cells, we demonstrate that apically aEPEC infection is followed by increased production of secreted MUC2 and MUC5AC mucins and membrane-bound MUC3 and MUC4 mucins. The transcription of the MUC5AC and MUC4 genes was transiently upregulated after aEPEC infection. We provide evidence that the apically adhering aEPEC cells exploit the mucins' increased production since they grew in the presence of membrane-bound mucins, whereas tEPEC did not. The data described herein report a putative new virulence phenomenon in aEPEC.

The role of the immune system in regulating the microbiota

A diverse population of bacteria, archaea and fungi, collectively known as the microbiota, abounds within the gastrointestinal tract of the mammalian host. This microbial population makes many important contributions to host physiology through inter-kingdom signalling and by providing nutrients that have both local and systemic effects. In a healthy state the overall host-microbial interaction is symbiotic; however, a growing number of diseases have been associated with a dysregulated microbiota. To avoid these consequences, the host exerts substantial effort to maintain proper regulation of the microbiota with respect to localization and composition. Although important to maintaining microbial balance, the host immune response can also be the cause of a disrupted microbiota, contributing to disease severity. Here, we discuss the role of the host in both maintaining and disrupting a balanced gastrointestinal microbiota.

Probiotics-host communication: Modulation of signaling pathways in the intestine

The intestinal microbiota includes a diverse group of functional microorganisms, including candidate probiotics or viable microorganisms that benefit the host. Beneficial effects of probiotics include enhancing intestinal epithelial cell function, protecting against physiologic stress, modulating cytokine secretion profiles, influencing T lymphocyte populations, and enhancing antibody secretion. Probiotics have demonstrated significant potential as therapeutic options for a variety of diseases, but the mechanisms responsible for these effects remain to be fully elucidated. Accumulating evidence demonstrates that probiotics communicate with the host by modulating key signaling pathways, such as NFκB and MAPK, to either enhance or suppress activation and influence downstream pathways. Beneficial microbes can profoundly alter the physiology of the gastrointestinal tract, and understanding these mechanisms may result in new diagnostic and therapeutic strategies.

Environmentally-acquired bacteria influence microbial diversity and natural innate immune responses at gut surfaces

Background

Early microbial colonization of the gut reduces the incidence of infectious, inflammatory and autoimmune diseases. Recent population studies reveal that childhood hygiene is a significant risk factor for development of inflammatory bowel disease, thereby reinforcing the hygiene hypothesis and the potential importance of microbial colonization during early life. The extent to which early-life environment impacts on microbial diversity of the adult gut and subsequent immune processes has not been comprehensively investigated thus far. We addressed this important question using the pig as a model to evaluate the impact of early-life environment on microbe/host gut interactions during development.

Results

Genetically-related piglets were housed in either indoor or outdoor environments or in experimental isolators. Analysis of over 3,000 16S rRNA sequences revealed major differences in mucosa-adherent microbial diversity in the ileum of adult pigs attributable to differences in early-life environment. Pigs housed in a natural outdoor environment showed a dominance of Firmicutes, in particular Lactobacillus, whereas animals housed in a hygienic indoor environment had reduced Lactobacillus and higher numbers of potentially pathogenic phylotypes. Our analysis revealed a strong negative correlation between the abundance of Firmicutes and pathogenic bacterial populations in the gut. These differences were exaggerated in animals housed in experimental isolators. Affymetrix microarray technology and Real-time Polymerase Chain Reaction revealed significant gut-specific gene responses also related to early-life environment. Significantly, indoor-housed pigs displayed increased expression of Type 1 interferon genes, Major Histocompatibility Complex class I and several chemokines. Gene Ontology and pathway analysis further confirmed these results.

Conclusion

Early-life environment significantly affects both microbial composition of the adult gut and mucosal innate immune function. We observed that a microbiota dominated by lactobacilli may function to maintain mucosal immune homeostasis and limit pathogen colonization.

Persistence of colicinogenic Escherichia coli in the mouse gastrointestinal tract

BACKGROUND

The ability of a bacterial strain to competitively exclude or displace other strains can be attributed to the production of narrow spectrum antimicrobials, the bacteriocins. In an attempt to evaluate the importance of bacteriocin production for Escherichia coli strain residence in the gastrointestinal tract, a murine model experimental evolution study was undertaken.

RESULTS

Six colicin-producing, yet otherwise isogenic, E. coli strains were administered and established in the large intestine of streptomycin-treated mice. The strains' persistence, population density, and doubling time were monitored over a period of 112 days. Early in the experiment only minor differences in population density between the various colicin-producing and the non-producing control strains were detected. However, over time, the density of the control strains plummeted, while that of the colicin-producing strains remained significantly higher (F(7,66) = 2.317; P < 0.0008).

CONCLUSION

The data presented here support prior claims that bacteriocin production may play a significant role in the colonization of E. coli in the gastrointestinal tract. Further, this study suggests that the ability to produce bacteriocins may prove to be a critical factor in determining the success of establishing probiotic E. coli in the gastrointestinal tract of humans and animals.

Unraveling mechanisms of action of probiotics

Probiotics are defined as living organisms that, when administered in sufficient numbers, are of benefit to the host. Current evidence indicates that varying probiotic strains mediate their effects by a variety of different effects that are dependent on the dosage employed as well as the route and frequency of delivery. Some probiotics act in the lumen of the gut by elaborating antibacterial molecules such as bacteriocins; others enhance the mucosal barrier by increasing the production of innate immune molecules, including goblet cell-derived mucins and trefoil factors and defensins produced by intestinal Paneth cells; and other probiotics mediate their beneficial effects by promoting adaptive immune responses (secretory immune globulin A, regulatory T cells, interleukin-10). Some probiotics have the capacity to activate receptors in the enteric nervous system, which could be used to promote pain relief in the setting of visceral hyperalgesia. Future development of the effective use of probiotics in treating various gastroenterological disorders in human participants should take advantage of this new knowledge. The creation of novel formulations of probiotics could be directed to effectively target certain mechanisms of actions that are altered in specific disease states.

Comparative analysis of attachment of Shiga-toxigenic Escherichia coli and Salmonella strains to cultured HT-29 and Caco-2 cell lines

The ability of Escherichia coli and Salmonella isolates to attach to Caco-2 and HT-29 cell monolayers was measured. All isolates displayed a greater ability to attach to Caco-2 cells than HT-29 cells, and overall E. coli isolates attached better to both cell lines than Salmonella isolates. Bacteria that were considered to be pathogenic displayed no greater ability to attach to cell lines than those that were not considered to be pathogenic. Additionally, no correlation was found between cell line attachment and previously determined hydrophobicity results.

Mucin dynamics in intestinal bacterial infection

BACKGROUND

Bacterial gastroenteritis causes morbidity and mortality in humans worldwide. Murine Citrobacter rodentium infection is a model for gastroenteritis caused by the human pathogens enteropathogenic Escherichia coli and enterohaemorrhagic E. coli. Mucin glycoproteins are the main component of the first barrier that bacteria encounter in the intestinal tract.

METHODOLOGY/PRINCIPAL FINDINGS

Using Immunohistochemistry, we investigated intestinal expression of mucins (Alcian blue/PAS, Muc1, Muc2, Muc4, Muc5AC, Muc13 and Muc3/17) in healthy and C. rodentium infected mice. The majority of the C. rodentium infected mice developed systemic infection and colitis in the mid and distal colon by day 12. C. rodentium bound to the major secreted mucin, Muc2, in vitro, and high numbers of bacteria were found in secreted MUC2 in infected animals in vivo, indicating that mucins may limit bacterial access to the epithelial surface. In the small intestine, caecum and proximal colon, the mucin expression was similar in infected and non-infected animals. In the distal colonic epithelium, all secreted and cell surface mucins decreased with the exception of the Muc1 cell surface mucin which increased after infection (p<0.05). Similarly, during human infection Salmonella St Paul, Campylobacter jejuni and Clostridium difficile induced MUC1 in the colon.

CONCLUSION

Major changes in both the cell-surface and secreted mucins occur in response to intestinal infection.

Prebiotics, probiotics, synbiotics in surgery--are they only trendy, truly effective or even dangerous?

BACKGROUND

Despite advances in surgical technique and intensive care medicine, nosocomial bacterial infections frequently occur in patients after major abdominal surgery and have a negative impact on operative outcome and hospital costs. In parallel, the routine use of antibiotics led to the development of resistance. Some probiotics (living bacteria) and prebiotics (fibers) are able to stabilize the intestinal barrier and prevent bacterial translocation and infections. The aim of this article was to review all available experience with pro- and prebiotics in surgical trials.

MATERIALS AND METHODS

Medical databases were searched for animal trials and randomized controlled studies with pro- and prebiotics in surgical patients. Primary endpoint of all reported studies was the occurrence of bacterial infections. In addition, type and concentration of the pro- and prebiotics, duration of therapy, adverse events, and other effects were investigated.

RESULTS

In three animal trials and in ten of the 15 clinical studies, probiotics or synbiotics led to a significant reduction of bacterial infection rates compared to the control groups. In two studies, there was a positive trend in the groups with synbiotics, but the results were not statistically significant. Two studies showed no effect, and in one study, the mortality rate was even higher in the synbiotic group. Except in the latter study, no severe adverse events were observed. The success of treatment depends on the synbiotic preparation and the length of therapy. Patients after surgery of the liver and pancreas and multiple trauma patients profited most from synbiotic treatment.

CONCLUSION

The existing randomized controlled trials demonstrated a positive effect of synbiotics in patients with high-risk operations; however, synbiotic preparations should be extensively tested before using them in clinical trials.

Lactobacillus bulgaricus prevents intestinal epithelial cell injury caused by Enterobacter sakazakii-induced nitric oxide both in vitro and in the newborn rat model of necrotizing enterocolitis

Enterobacter sakazakii is an emerging pathogen that has been associated with outbreaks of necrotizing enterocolitis (NEC) as well as infant sepsis and meningitis. Our previous studies demonstrated that E. sakazakii induces NEC in a newborn rat model by inducing enterocyte apoptosis. However, the mechanisms responsible for enterocyte apoptosis are not known. Here we demonstrate that E. sakazakii induces significant production of nitric oxide (NO) in rat intestinal epithelial cells (IEC-6) upon infection. The elevated production of NO, which is due to increased expression of inducible NO synthase, is responsible for apoptosis of IEC-6 cells. Notably, pretreatment of IEC-6 cells with Lactobacillus bulgaricus (ATCC 12278) attenuated the upregulation of NO production and thereby protected the cells from E. sakazakii-induced apoptosis. Furthermore, pretreatment with L. bulgaricus promoted the integrity of enterocytes both in vitro and in the infant rat model of NEC, even after challenge with E. sakazakii. Infection of IEC-6 cells with E. sakazakii upregulated several genes related to apoptosis, cytokine production, and various signaling pathways, as demonstrated by rat gene array analysis, and this upregulation was subdued by pretreatment with L. bulgaricus. In agreement with these data, L. bulgaricus pretreatment protected newborn rats infected with E. sakazakii from developing NEC, resulting in improved survival.

Interactions of the intestinal epithelium with the pathogen and the indigenous microbiota: a three-way crosstalk

The mucosal surfaces of the gastrointestinal tract harbor a vast number of commensal microbiota that have coevolved with the host, and in addition display one of the most complex relationships with the host. This relationship affects several important aspects of the biology of the host including the synthesis of nutrients, protection against infection, and the development of the immune system. On the other hand, despite the existence of several lines of mucosal defense mechanisms, pathogenic organisms such as Shigella and Salmonella have evolved sophisticated virulence strategies for breaching these barriers. The constant challenge from these pathogens and the attempts by the host to counter them set up a dynamic equilibrium of cellular and molecular crosstalk. Even slight perturbations in this equilibrium may be detrimental to the host leading to severe bacterial infection or even autoimmune diseases like inflammatory bowel disease. Several experimental model systems, including germ-free mice and antibiotic-treated mice, have been used by various researchers to study this complex relationship. Although it is only the beginning, it promises to be an exciting era in the study of these host-microbe relationships.

Interactions between commensal bacteria and the gut-associated immune system of the chicken

The chicken gut-associated lymphoid tissue is made up of a number of tissues and cells that are responsible for generating mucosal immune responses and maintaining intestinal homeostasis. The normal chicken microbiota also contributes to this via the ability to activate both innate defense mechanisms and adaptive immune responses. If left uncontrolled, immune activation in response to the normal microbiota would pose a risk of excessive inflammation and intestinal damage. Therefore, it is important that immune responses to the normal microbiota be under strict regulatory control. Through studies of mammals, it has been established that the mucosal immune system has specialized regulatory and anti-inflammatory mechanisms for eliminating or tolerating the normal microbiota. The mechanisms that exist in the chicken to control host responses to the normal microbiota, although assumed to be similar to that of mammals, have not yet been fully described. This review summarizes what is currently known about the host response to the intestinal microbiota, particularly in the chicken.

Do you have a probiotic in your future?

The possibility of using microbes to maintain health, and to prevent or treat disease is a topic as old as microbiology. However, one factor impeding the introduction of effective probiotics has been our very limited understanding of the composition of the human microbiome, as well as the biological requirements for these organisms. With advances in understanding the microbiome and its metagenome in humans and other mammals, we now can build a more robust scientific basis to develop probiotic strategies. Increasing knowledge of intramicrobial competition and cooperation, as well as host-microbe cross-signaling, will facilitate design of new probiotics and the modeling of their deployment, leading to eventual clinical trials.

Effect of the administration of a fermented milk containing Lactobacillus casei DN-114001 on intestinal microbiota and gut associated immune cells of nursing mice and after weaning until immune maturity

Background

Microbial colonization of the intestine after birth is an important step for the development of the gut immune system. The acquisition of passive immunity through breast-feeding may influence the pattern of bacterial colonization in the newborn. The aim of this work was to evaluate the effect of the administration of a probiotic fermented milk (PFM) containing yogurt starter cultures and the probiotic bacteria strain Lactobacillus casei DN-114001 to mothers during nursing or their offspring, on the intestinal bacterial population and on parameters of the gut immune system.

Results

Fifteen mice of each group were sacrificed at ages 12, 21, 28 and 45 days. Large intestines were taken for determination of intestinal microbiota, and small intestines for the study of secretory-IgA (S-IgA) in fluid and the study of IgA+ cells, macrophages, dendritic cells and goblet cells on tissue samples. The consumption of the PFM either by the mother during nursing or by the offspring after weaning modified the development of bifidobacteria population in the large intestine of the mice. These modifications were accompanied with a decrease of enterobacteria population. The administration of this PFM to the mothers improved their own immune system and this also affected their offspring. Offspring from mice that received PFM increased S-IgA in intestinal fluids, which mainly originated from their mother's immune system. A decrease in the number of macrophages, dendritic cells and IgA+ cells during the suckling period in offspring fed with PFM was observed; this could be related with the improvement of the immunity of the mothers, which passively protect their babies. At day 45, the mice reach maturity of their own immune system and the effects of the PFM was the stimulation of their mucosal immunity.

Conclusion

The present work shows the beneficial effect of the administration of a PFM not only to the mothers during the suckling period but also to their offspring after weaning and until adulthood. This effect positively improved the intestinal microbiota that are related with a modulation of the gut immune response, which was demonstrated with the stimulation of the IgA + cells, macrophages and dendritic cells.

Rationale for probiotic treatment strategies in inflammatory bowel disease

Chronic inflammatory bowel diseases (IBD), such as Crohn's disease and ulcerative colitis, are recurrent and aggressive inflammatory disorders that are most likely the result of an overly aggressive immune response to ubiquitous intestinal antigens in a genetically susceptible host. Despite decades of intense research, our knowledge of factors causing IBD remains incomplete and, therefore, conventional therapy to induce and maintain remission works in a symptomatic fashion, merely suppressing the immune response. Probiotic bacteria have long been known to confer health benefits, especially with regard to intestinal disorders. Although there is mounting evidence from in vitro and animal experiments supporting the use of probiotics in IBD, clinical trials have not provided definite evidence for the therapeutic effect of probiotic therapy in IBD to date. This is with the notable exception of pouchitis and the maintenance of remission in ulcerative colitis, whereas Crohn's disease and active ulcerative colitis do not seem amenable to probiotic intervention. The next 5 years will see more trials targeting specific clinical settings using tailor-made probiotic combinations, taking into account our increasing knowledge of individual probiotic properties and the diversity of these microorganisms.

Probiotics in clinical practice: an overview

The observation that intestinal bacterial microflora might be able to influence immune system surveillance through changed nutritional habits has raised awareness of the role of probiotics. These are live microorganisms that are able to reach the gastrointestinal tract and alter its microfloral composition, producing beneficial health effects when consumed in adequate amounts. Recent clinical trials have evaluated the clinical effectiveness of probiotics in the treatment and prevention of a wide range of acute and chronic gastrointestinal diseases, and also non-gastrointestinal diseases, such as atopy, respiratory infections, vaginitis and hypercholesterolaemia. Probiotic supplements are generally regarded as safe because the microorganisms they contain are identical to those found in human gastrointestinal and vaginal microflora. Guidelines on the use of probiotics in the clinical setting require periodical updates for the latest data to be included in clinical applications. The purpose of this clinical report is to review current evidence on the use of probiotics in a variety of gastrointestinal and non-gastrointestinal conditions.

The role of probiotics in management of irritable bowel syndrome

Irritable bowel syndrome (IBS) affects a significant proportion of the North American population; however, the etiology and pathophysiology of this disease remain poorly understood, and treatment is focused on symptom management. Over the years, research has revealed that the bacterial flora in the human gut interact with the bowel in a complex and dynamic relationship and may be responsible for the induction and progression of some of the pathophysiologic aspects of IBS. Probiotics are nonpathogenic bacteria that benefit the host, and the roles they can play in the bacterio-gut relationship provide hope of a safe treatment that would allow for modulation of IBS disease states. Probiotic treatment for IBS has undergone significant exploration, yet the exact therapeutic effects and doses of these beneficial bacteria remain unclear due to the conflicting nature of available evidence. This review discusses the evidence from randomized controlled trials on probiotic treatment of IBS and presents the current understanding of the mechanisms of action of probiotics as they apply to IBS and provides a plausible explanation for the variability in evidence documented by the various trials under review.

Role of the intestinal barrier in inflammatory bowel disease

A critical function of the intestinal mucosa is to form a barrier that separates luminal contents from the interstitium. The single layer of intestinal epithelial cells (IECs) serves as a dynamic interface between the host and its environment. Cell polarity and structural properties of the epithelium is complex and is important in the development of epithelial barrier function. Epithelial cells associate with each other via a series of intercellular junctions. The apical most intercellular junctional complex referred to as the Apical Junction Complex (AJC) is important in not only cell-cell recognition, but also in the regulation of paracellular movement of fluid and solutes. Defects in the intestinal epithelial barrier function have been observed in a number of intestinal disorders such as inflammatory bowel disease (IBD). It is now becoming evident that an aberrant epithelial barrier function plays a central role in the pathophysiology of IBD. Thus, a better understanding of the intestinal epithelial barrier structure and function in healthy and disease states such as IBD will foster new ideas for the development of therapies for such chronic disorders.

Mucins in the mucosal barrier to infection

The mucosal tissues of the gastrointestinal, respiratory, reproductive, and urinary tracts, and the surface of the eye present an enormous surface area to the exterior environment. All of these tissues are covered with resident microbial flora, which vary considerably in composition and complexity. Mucosal tissues represent the site of infection or route of access for the majority of viruses, bacteria, yeast, protozoa, and multicellular parasites that cause human disease. Mucin glycoproteins are secreted in large quantities by mucosal epithelia, and cell surface mucins are a prominent feature of the apical glycocalyx of all mucosal epithelia. In this review, we highlight the central role played by mucins in accommodating the resident commensal flora and limiting infectious disease, interplay between underlying innate and adaptive immunity and mucins, and the strategies used by successful mucosal pathogens to subvert or avoid the mucin barrier, with a particular focus on bacteria.

Modulation of intestinal goblet cell function during infection by an attaching and effacing bacterial pathogen

The attaching and effacing (A/E) bacterial pathogens enteropathogenic Escherichia coli and enterohemorrhagic E. coli and the related mouse pathogen Citrobacter rodentium colonize their hosts' intestines by infecting the apical surfaces of enterocytes, subverting their function, and they ultimately cause diarrhea. Surprisingly, little is known about the interactions of these organisms with goblet cells, which are specialized epithelial cells that secrete the protective molecules Muc2 and trefoil factor 3 (Tff3) into the intestinal lumen. C. rodentium infection leads to dramatic goblet cell depletion within the infected colon, yet it is not clear whether C. rodentium infects goblet cells or if this pathology is pathogen or host mediated. As determined by immunostaining and PCR, both the number of goblet cells and the expression of genes encoding Muc2 and Tff3 were significantly reduced by day 10 postinfection. While electron microscopy and immunostaining revealed that C. rodentium directly infected a fraction of colonic goblet cells, C. rodentium localization did not correlate with goblet cell depletion. To assess the role of the host immune system in these changes, Rag1 knockout (KO) (T- and B-cell-deficient) mice were infected with C. rodentium. Rag1 KO mice did not exhibit the reduction in the number of goblet cells or in mediator (Muc2 and Tff3) expression observed in infected immunocompetent mice. However, reconstitution of Rag1 KO mice with T and B lymphocytes from C57BL/6 mice restored the goblet cell depletion phenotype during C. rodentium infection. In conclusion, these studies demonstrated that while colonic goblet cells can be subject to direct infection and potential subversion by A/E pathogens in vivo, it is the host immune system that primarily modulates the function of these cells during infection.

Host protein binding and adhesive properties of H6 and H7 flagella of attaching and effacing Escherichia coli

It had been suggested that the flagella of enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) might contribute to host colonization. In this study, we set out to investigate the adhesive properties of H7 and H6 flagella. We studied the abilities of EHEC EDL933 (O157:H7) and EPEC E2348/69 (O127:H6) flagella to bind to bovine mucus, host proteins such as mucins, and extracellular matrix proteins. Through several approaches, we found that H6 and H7 flagella and their flagellin monomers bind to mucins I and II and to freshly isolated bovine mucus. A genetic approach showed that EHEC and EPEC fliC deletion mutants were significantly less adherent to bovine intestinal tissue than the parental wild-type strains. In addition, we found that EPEC bacteria and H6 flagella, but not EHEC, bound largely, in a dose-dependent manner, to collagen and to a lesser extent to laminin and fibronectin. We also report that EHEC O157:H7 strains agglutinate rabbit red blood cells via their flagella, a heretofore unknown phenotype in this pathogroup. Collectively, our data demonstrate that the H6 and H7 flagella possess adhesive properties, particularly the ability to bind mucins, that may contribute to colonization of mucosal surfaces.

Use of probiotics in pediatrics: rationale, mechanisms of action, and practical aspects

The use of probiotics (ingested microbes that can modify intestinal microbial populations in a way that benefit the host) has moved from concept to actual demonstration of specific benefits by specific microorganisms for specific populations. It is increasingly clear that these benefits to the host are mostly mediated by the profound effect that intestinal microflora (microbiota) have on gut barrier function and host immune response. Intestinal bacteria are more numerous than the human cells of the host that harbors them. Despite having many potential pathogens in this microflora, humans do not routinely get infected. It is no coincidence that gut-associated immune tissue constitutes approximately 80% of all immunologically active cells in the human host. The gut interacts with intestinal bacteria, both resident and ingested, to develop protective mechanisms (via improving gut barrier function and immune stimulation for defense) and appropriate, nonexaggerated responses (via immune modulation and immune tolerance) to support host health. The mechanisms of this interaction between host and bacteria are increasingly being unraveled and in great part explain the clinical benefits that have been reported with specific probiotic bacteria by enhancing host defense mechanisms (such as for treatment and prevention of viral diarrhea and reducing risk of necrotizing enterocolitis), mitigating antibiotic-associated diarrhea, and modulating host immune response (such as in allergic disease).

Probiotic treatment of vancomycin-resistant enterococci: a randomised controlled trial

OBJECTIVE

To determine whether eating Lactobacillus rhamnosus GG (LGG) in the form of commercially available yoghurt improves clearance of vancomycin-resistant enterococci (VRE).

DESIGN

Double-blind, randomised, placebo-controlled trial.

SETTING

Renal ward of Austin Health, a tertiary hospital, Feb-Oct 2005.

PARTICIPANTS

27 VRE-positive patients, 14 receiving active treatment and 13 controls.

INTERVENTIONS

Subjects were randomly assigned to either a treatment group (receiving 100 g daily of yoghurt containing LGG for 4 weeks) or a control group (receiving standard pasteurised yoghurt). Faecal samples were obtained three times at about weekly intervals. Treated patients were tested for VRE again at 8 weeks. Patients in the control group who had failed to clear VRE after 4 weeks were then given LGG-containing yoghurt for 4 weeks, as an open continuation.

MAIN OUTCOME MEASURE

Number of faecal specimens clear of VRE.

RESULTS

Of the 27 patients enrolled, 23 completed the study. Two patients were lost to follow-up, one died and one withdrew. All 11 patients in the treatment group who completed the study cleared VRE. Three subjects reverted to VRE positivity after using antibiotics to which LGG is sensitive, while all others remained negative for at least 4 weeks after trial completion. Twelve control subjects completed the study, of whom one cleared VRE and 11 remained VRE-positive. Eight of these 11 patients were subsequently crossed over to receive LGG yoghurt, and all cleared VRE within 4 weeks.

CONCLUSION

To our knowledge, this is the first description of a probiotic therapy to successfully treat gastrointestinal carriage of VRE in renal patients. Further investigation of the use of LGG in VRE-positive patients is warranted.

Probiotics affect virulence-related gene expression in Escherichia coli O157:H7

The attachment of enterohemorrhagic Escherichia coli O157:H7 (EHEC O157) to host intestinal epithelial cells is essential for the development of hemorrhagic colitis and hemolytic-uremic syndrome in humans. Genes involved in attachment are carried within a pathogenicity island named the locus of enterocyte effacement (LEE), known to be directly activated by quorum sensing (QS). In the present study, we investigated autoinducer-2 (AI-2) production and the expression of several virulence-related genes in EHEC O157 grown in the absence and presence of a Lactobacillus acidophilus-secreted molecule(s). Transcription of important EHEC O157 virulence-related genes was studied by constructing promoter-reporter fusions and reverse transcriptase PCR. Shiga toxin (Stx) production was assayed by an enzyme immunoassay. When EHEC O157 was grown in the presence of chromatographically selected fractions of L. acidophilus La-5 cell-free spent medium, we observed a significant reduction of both extracellular AI-2 concentration and the expression of important virulence-related genes, although no significant difference in Stx production was observed. We show here that L. acidophilus La-5 secretes a molecule(s) that either acts as a QS signal inhibitor or directly interacts with bacterial transcriptional regulators, controlling the transcription of EHEC O157 genes involved in colonization.

Bacteriocin production as a mechanism for the antiinfective activity of Lactobacillus salivarius UCC118

The mechanisms by which probiotic strains enhance the health of the host remain largely uncharacterized. Here we demonstrate that Lactobacillus salivarius UCC118, a recently sequenced and genetically tractable probiotic strain of human origin, produces a bacteriocin in vivo that can significantly protect mice against infection with the invasive foodborne pathogen Listeria monocytogenes. A stable mutant of Lb. salivarius UCC118 that is unable to produce the Abp118 bacteriocin also failed to protect mice against infection with two strains of L. monocytogenes, EGDe and LO28, confirming that bacteriocin production is the primary mediator of protection against this organism. Furthermore, Lb. salivarius UCC118 did not offer any protection when mice were infected with a strain of L. monocytogenes expressing the cognate Abp118 immunity protein AbpIM, confirming that the antimicrobial effect is a result of direct antagonism between Lb. salivarius and the pathogen, mediated by the bacteriocin Abp118.

Enhancement of gastric mucosal integrity by Lactobacillus rhamnosus GG

The gastric mucosa is frequently exposed to different exogenous and endogenous ulcerative agents. Alcoholism is one of the risk factors for the development of mucosal damage in the stomach. This study aimed to assess if a probiotic strain Lactobacillus rhamnosus GG (LGG) is capable of protecting the gastric mucosa from acute damage induced by intragastric administration of ethanol. Pre-treatment of rats with LGG at 10(9) cfu/ml twice daily for three consecutive days markedly reduced ethanol-induced mucosal lesion area by 45%. LGG pre-treatment also significantly increased the basal mucosal prostaglandin E(2) (PGE(2)) level. In addition, LGG attenuated the suppressive actions of ethanol on mucus-secreting layer and transmucosal resistance and reduced cellular apoptosis in the gastric mucosa. It is suggested that the protective action of LGG on ethanol-induced gastric mucosal lesions is likely attributed to the up-regulation of PGE(2), which could stimulate the mucus secretion and increase the transmucosal resistance in the gastric mucosa. All these would protect mucosal cells from apoptosis in the stomach.

Induction of human beta-defensin 2 by the probiotic Escherichia coli Nissle 1917 is mediated through flagellin

Human beta-defensin 2 (hBD-2) is an inducible antimicrobial peptide synthesized by the epithelium to counteract bacterial adherence and invasion. Proinflammatory cytokines, as well as certain bacterial strains, have been identified as potent endogenous inducers. Recently, we have found that hBD-2 induction by probiotic Escherichia coli Nissle 1917 was mediated through NF-kappaB- and AP-1-dependent pathways. The aim of the present study was to identify the responsible bacterial factor. E. coli Nissle 1917 culture supernatant was found to be more potent than the pellet, indicating a soluble or shed factor. Chemical analysis demonstrated the factor to be heat resistant and proteinase digestible. Several E. coli Nissle 1917 deletion mutants were constructed and tested for their ability to induce hBD-2 expression in Caco-2 cells. Deletion mutants for flagellin specifically exhibited an impaired immunostimulatory capacity. Reinsertion of the flagellin gene restored the induction capacity to normal levels. Isolated flagellin from E. coli Nissle 1917 and from Salmonella enterica serovar Enteritidis induced hBD-2 mRNA significantly in contrast to the flagellin of the apathogenic E. coli strain ATCC 25922. H1 flagellin antiserum abrogated hBD-2 expression induced by flagellin as well as E. coli Nissle 1917 supernatant, confirming that flagellin is the major stimulatory factor of E. coli Nissle 1917.

Oral administration of probiotic bacteria (E. coli Nissle, E. coli O83, Lactobacillus casei) influences the severity of dextran sodium sulfate-induced colitis in BALB/c mice

Our study examined whether repeated preventive oral administration of live probiotic bacterial strains Escherichia coli O83:K24:H31 (Ec O83), Escherichia coli Nissle 1917 O6:K5:H1 (Ec Nis) and Lactobacillus casei DN 114001 (Lc) can protect mice against dextran sodium sulfate (DSS)-induced colitis. A significant decrease in average symptom score was observed in Ec O83-, Ec Nis- and Lc-pretreated group (p < 0.05). Significant differences in body mass loss between Lc pretreated mice with DSS-induced colitis were found when compared with nontreated mice (p < 0.05). PBS pretreated mice had a significantly shorter colon than Ec O83-, Ec Nis- and Lc-pretreated mice (p < 0.05). Administration of Lc significantly decreased the severity of DSS induced histological marks of inflammation (p < 0.05). A significant difference (p < 0.05) was also found in specific IgA level against given probiotic in enteral fluid between colitic mice and healthy mice pretreated with Ec 083 and Ec Nis.

Probiotics and inflammatory bowel diseases

Enteric microflora profiles vary considerably between active inflammatory bowel diseases (IBD) and healthy conditions. Intestinal microflora may partake in the pathogenesis of IBD by one or some ways: specific pathogenic infection induces abnormal intestinal mucosal inflammation; aberrant microflora components trigger the onset of IBD; abnormal host immune response loses normal immune tolerance to luminal components; luminal antigens permeate through the defective mucosal barrier into mucosal lamina propria and induce abnormal inflammatory response. Preliminary studies suggest that administration of probiotics may be benefit for experimental colitis and clinical trials for IBD. Researches have been studying the function of probiotics. Introduction of probiotics can balance the aberrant enteric microflora in IBD patients, and reinforce the various lines of intestinal defence by inhibiting microbial pathogens growth, increasing intestinal epithelial tight junction and permeability, modulating immune response of intestinal epithelia and mucosal immune cells, secreting antimicrobial products, decomposing luminal pathogenic antigens.

VSL#3 probiotic mixture: a review of its use in chronic inflammatory bowel diseases

VSL#3 (VSL#3) is a high-concentration probiotic preparation of eight live freeze-dried bacterial species that are normal components of the human gastrointestinal microflora, including four strains of lactobacilli (Lactobacillus casei, L. plantarum, L. acidophilus and L. delbrueckii subsp. bulgaricus), three strains of bifidobacteria (Bifidobacterium longum, B. breve and B. infantis) and Streptococcus salivarius subsp. thermophilus. Data from noncomparative trials suggest that VSL#3 has clinical potential in the treatment of active mild to moderate ulcerative colitis and as maintenance therapy for patients with ulcerative colitis in remission. In addition, a randomised, open-label, multicentre trial showed that VSL#3 in combination with low-dose balsalazide (a prodrug of mesalazine [mesalamine; 5-aminosalicylic acid]) was more effective than standard doses of basalazide or mesalazine monotherapy in the treatment of acute mild to moderate ulcerative colitis. Randomised, double-blind, placebo-controlled studies have shown VSL#3 is effective in preventing the onset of acute pouchitis in patients with newly formed surgical pouches, and in maintaining remission following antibacterial treatment of acute pouchitis in patients with a history of refractory or recurrent pouchitis. Treatment guidelines from the US and the UK include VSL#3 as a therapeutic option for the prevention of pouchitis relapse in patients with chronic pouchitis. In general, VSL#3 was well tolerated in clinical trials. Large, well designed, controlled confirmatory clinical trials will further determine the place of VSL#3 in the treatment of ulcerative colitis.