Control of pathogens and pathobionts by the gut microbiota.
TL;DR: The mechanisms that regulate the ability of the microbiota to restrain pathogen growth are complex and include competitive metabolic interactions, localization to intestinal niches and induction of host immune responses.
Abstract: A dense resident microbial community in the gut, referred as the commensal microbiota, coevolved with the host and is essential for many host physiological processes that include enhancement of the intestinal epithelial barrier, development of the immune system and acquisition of nutrients. A major function of the microbiota is protection against colonization by pathogens and overgrowth of indigenous pathobionts that can result from the disruption of the healthy microbial community. The mechanisms that regulate the ability of the microbiota to restrain pathogen growth are complex and include competitive metabolic interactions, localization to intestinal niches and induction of host immune responses. Pathogens, in turn, have evolved strategies to escape from commensal-mediated resistance to colonization. Thus, the interplay between commensals and pathogens or indigenous pathobionts is critical for controlling infection and disease. Understanding pathogen-commensal interactions may lead to new therapeutic approaches to treating infectious diseases.
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TL;DR: In high-income countries, overuse of antibiotics, changes in diet, and elimination of constitutive partners, such as nematodes, may have selected for a microbiota that lack the resilience and diversity required to establish balanced immune responses.
3,257 citations
Cites background from "Control of pathogens and pathobiont..."
...Alteration of nutrient availability by thehostmicrobiota canalsohaveprofound consequences on the expression of virulence genes and growth rateof pathogenssuchasenterohemorragicE. coliorClostridium difficile (Kamada et al., 2013; Ng et al., 2013; Pacheco et al., 2012)....
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...Consequently, commensals have been shown to limit pathogen colonization though competition for defined metabolites in a process referred to as colonization resistance (Kamada et al., 2013)....
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...Consequently, commensals have been shown to limit pathogen colonization through competition for defined metabolites in a process referred to as colonization resistance (Kamada et al., 2013)....
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TL;DR: The large majority of studies on the role of the microbiome in the pathogenesis of disease are correlative and preclinical; several have influenced clinical practice.
Abstract: The large majority of studies on the role of the microbiome in the pathogenesis of disease are correlative and preclinical; several have influenced clinical practice.
2,083 citations
TL;DR: Future studies will focus on understanding the mechanisms underlying the microbiota-gut-brain axis and attempt to elucidate microbial-based intervention and therapeutic strategies for neuropsychiatric disorders.
Abstract: The importance of the gut-brain axis in maintaining homeostasis has long been appreciated. However, the past 15 yr have seen the emergence of the microbiota (the trillions of microorganisms within ...
1,775 citations
TL;DR: An overview of microbial SCFAs production and their effects on the intestinal mucosa with specific emphasis on their relevance for Inflammatory Bowel Diseases is presented and the therapeutic potential ofSCFAs for IBD is discussed.
Abstract: Ulcerative colitis (UC) and Crohn's disease (CD), collectively known as Inflammatory Bowel Diseases (IBD), are caused by a complex interplay between genetic, immunologic, microbial and environmental factors. Dysbiosis of the gut microbiome is increasingly considered to be causatively related to IBD and is strongly affected by components of a Western life style. Bacteria that ferment fibers and produce short chain fatty acids (SCFAs) are typically reduced in mucosa and feces of patients with IBD, as compared to healthy individuals. SCFAs, such as acetate, propionate and butyrate, are important metabolites in maintaining intestinal homeostasis. Several studies have indeed shown that fecal SCFAs levels are reduced in active IBD. SCFAs are an important fuel for intestinal epithelial cells and are known to strengthen the gut barrier function. Recent findings, however, show that SCFAs, and in particular butyrate, also have important immunomodulatory functions. Absorption of SCFAs is facilitated by substrate transporters like MCT1 and SMCT1 to promote cellular metabolism. Moreover, SCFAs may signal through cell surface G-protein coupled receptors (GPCRs), like GPR41, GPR43, and GPR109A, to activate signaling cascades that control immune functions. Transgenic mouse models support the key role of these GPCRs in controlling intestinal inflammation. Here, we present an overview of microbial SCFAs production and their effects on the intestinal mucosa with specific emphasis on their relevance for IBD. Moreover, we discuss the therapeutic potential of SCFAs for IBD, either applied directly or by stimulating SCFAs-producing bacteria through pre- or probiotic approaches.
1,732 citations
Cites background from "Control of pathogens and pathobiont..."
...The bacterial community participates in maintaining intestinal homeostasis through the “training” of the immune system and inhibiting growth of pathogens and pathobionts (11, 12)....
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TL;DR: Current knowledge and emerging mechanisms governing oral polymicrobial synergy and dysbiosis that have both enhanced the understanding of pathogenic mechanisms and aided the design of innovative therapeutic approaches for oral diseases are discussed.
Abstract: The dynamic and polymicrobial oral microbiome is a direct precursor of diseases such as dental caries and periodontitis, two of the most prevalent microbially induced disorders worldwide. Distinct microenvironments at oral barriers harbour unique microbial communities, which are regulated through sophisticated signalling systems and by host and environmental factors. The collective function of microbial communities is a major driver of homeostasis or dysbiosis and ultimately health or disease. Despite different aetiologies, periodontitis and caries are each driven by a feedforward loop between the microbiota and host factors (inflammation and dietary sugars, respectively) that favours the emergence and persistence of dysbiosis. In this Review, we discuss current knowledge and emerging mechanisms governing oral polymicrobial synergy and dysbiosis that have both enhanced our understanding of pathogenic mechanisms and aided the design of innovative therapeutic approaches for oral diseases.
938 citations
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TL;DR: Few microorganisms are as versatile as Escherichia coli; it can also be a highly versatile, and frequently deadly, pathogen.
Abstract: Few microorganisms are as versatile as Escherichia coli. An important member of the normal intestinal microflora of humans and other mammals, E. coli has also been widely exploited as a cloning host in recombinant DNA technology. But E. coli is more than just a laboratory workhorse or harmless intestinal inhabitant; it can also be a highly versatile, and frequently deadly, pathogen. Several different E. coli strains cause diverse intestinal and extraintestinal diseases by means of virulence factors that affect a wide range of cellular processes.
4,583 citations
TL;DR: The authors showed that colonisation of mice with a segmented filamentous bacterium (SFB) is sufficient to induce the appearance of CD4+ T helper cells that produce IL-17 and IL-22 (Th17 cells) in the lamina propria.
3,860 citations
TL;DR: The infusion of donor feces was significantly more effective for the treatment of recurrent C. difficile infection than the use of vancomycin and patients showed increased fecal bacterial diversity, similar to that in healthy donors, with an increase in Bacteroidetes species and clostridium clusters IV and XIVa and a decrease in Proteobacteria species.
Abstract: A b s t r ac t Results The study was stopped after an interim analysis. Of 16 patients in the infusion group, 13 (81%) had resolution of C. difficile-associated diarrhea after the first infu - sion. The 3 remaining patients received a second infusion with feces from a differ- ent donor, with resolution in 2 patients. Resolution of C. difficile infection occurred in 4 of 13 patients (31%) receiving vancomycin alone and in 3 of 13 patients (23%) receiving vancomycin with bowel lavage (P<0.001 for both comparisons with the infusion group). No significant differences in adverse events among the three study groups were observed except for mild diarrhea and abdominal cramping in the in- fusion group on the infusion day. After donor-feces infusion, patients showed in- creased fecal bacterial diversity, similar to that in healthy donors, with an increase in Bacteroidetes species and clostridium clusters IV and XIVa and a decrease in Proteobacteria species. Conclusions The infusion of donor feces was significantly more effective for the treatment of recurrent C. difficile infection than the use of vancomycin. (Funded by the Nether- lands Organization for Health Research and Development and the Netherlands Organization for Scientific Research; Netherlands Trial Register number, NTR1177.)
3,081 citations
TL;DR: This study illustrates how combining comparative metagenomics with gnotobiotic mouse models and specific dietary manipulations can disclose the niches of previously uncharacterized members of the gut microbiota.
2,578 citations
TL;DR: It is found that lateral gene transfer is far more extensive than previously anticipated and 1,387 new genes encoded in strain-specific clusters of diverse sizes were found in O157:H7, including candidate virulence factors, alternative metabolic capacities, several prophages and other new functions—all of which could be targets for surveillance.
Abstract: The bacterium Escherichia coli O157:H7 is a worldwide threat to public health and has been implicated in many outbreaks of haemorrhagic colitis, some of which included fatalities caused by haemolytic uraemic syndrome. Close to 75,000 cases of O157:H7 infection are now estimated to occur annually in the United States. The severity of disease, the lack of effective treatment and the potential for large-scale outbreaks from contaminated food supplies have propelled intensive research on the pathogenesis and detection of E. coli O157:H7 (ref. 4). Here we have sequenced the genome of E. coli O157:H7 to identify candidate genes responsible for pathogenesis, to develop better methods of strain detection and to advance our understanding of the evolution of E. coli, through comparison with the genome of the non-pathogenic laboratory strain E. coli K-12 (ref. 5). We find that lateral gene transfer is far more extensive than previously anticipated. In fact, 1,387 new genes encoded in strain-specific clusters of diverse sizes were found in O157:H7. These include candidate virulence factors, alternative metabolic capacities, several prophages and other new functions--all of which could be targets for surveillance.
2,011 citations