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World Journal of Gastroenterology Nov 2014The potential for the positive manipulation of the gut microbiome through the introduction of beneficial microbes, as also known as probiotics, is currently an active... (Review)
Review
The potential for the positive manipulation of the gut microbiome through the introduction of beneficial microbes, as also known as probiotics, is currently an active area of investigation. The FAO/WHO define probiotics as live microorganisms that confer a health benefit to the host when administered in adequate amounts. However, dead bacteria and bacterial molecular components may also exhibit probiotic properties. The results of clinical studies have demonstrated the clinical potential of probiotics in many pathologies, such as allergic diseases, diarrhea, inflammatory bowel disease and viral infection. Several mechanisms have been proposed to explain the beneficial effects of probiotics, most of which involve gene expression regulation in specific tissues, particularly the intestine and liver. Therefore, the modulation of gene expression mediated by probiotics is an important issue that warrants further investigation. In the present paper, we performed a systematic review of the probiotic-mediated modulation of gene expression that is associated with the immune system and inflammation. Between January 1990 to February 2014, PubMed was searched for articles that were published in English using the MeSH terms "probiotics" and "gene expression" combined with "intestines", "liver", "enterocytes", "antigen-presenting cells", "dendritic cells", "immune system", and "inflammation". Two hundred and five original articles matching these criteria were initially selected, although only those articles that included specific gene expression results (77) were later considered for this review and separated into three major topics: the regulation of immunity and inflammatory gene expression in the gut, in inflammatory diseases of the gut and in the liver. Particular strains of Bifidobacteria, Lactobacilli, Escherichia coli, Propionibacterium, Bacillus and Saccharomyces influence the gene expression of mucins, Toll-like receptors, caspases, nuclear factor-κB, and interleukins and lead mainly to an anti-inflammatory response in cultured enterocytes. In addition, the interaction of commensal bacteria and probiotics with the surface of antigen-presenting cells in vitro results in the downregulation of pro-inflammatory genes that are linked to inflammatory signaling pathways, whereas other anti-inflammatory genes are upregulated. The effects of probiotics have been extensively investigated in animal models ranging from fish to mice, rats and piglets. These bacteria induce a tolerogenic and hyporesponsive immune response in which many genes that are related to the immune system, in particular those genes expressing anti-inflammatory cytokines, are upregulated. By contrast, information related to gene expression in human intestinal cells mediated by the action of probiotics is scarce. There is a need for further clinical studies that evaluate the mechanism of action of probiotics both in healthy humans and in patients with chronic diseases. These types of clinical studies are necessary for addressing the influence of these microorganisms in gene expression for different pathways, particularly those that are associated with the immune response, and to better understand the role that probiotics might have in the prevention and treatment of disease.
Topics: Animals; Bacteria; Disease Models, Animal; Gene Expression Regulation; Host-Pathogen Interactions; Humans; Inflammation Mediators; Inflammatory Bowel Diseases; Intestinal Mucosa; Intestines; Liver; Liver Diseases; Probiotics
PubMed: 25400447
DOI: 10.3748/wjg.v20.i42.15632 -
Zoonoses and Public Health Mar 2015Human illness due to infections with Escherichia coli O157 is a serious health concern. Infection occurs through direct contact with infected animals or their faeces,... (Meta-Analysis)
Meta-Analysis Review
Human illness due to infections with Escherichia coli O157 is a serious health concern. Infection occurs through direct contact with infected animals or their faeces, through contaminated food or water and/or through person-to-person transmission. A reduction in faecal E. coli O157 shedding in cattle might reduce the burden of human infections. We used systematic review and meta-analysis to assess the efficacy of direct-fed microbials (DFM), compared with placebo or no treatment, fed during the pre-harvest stage of production in reducing faecal E. coli O157 shedding in beef cattle during field trials. Four electronic databases, Nebraska Beef Reports and review article reference lists were searched. A total of 16 publications assessing faecal shedding at the end of the trial and/or throughout the trial period were included. The majority of publicly disseminated trials evaluated the prevalence of E. coli O157 faecal shedding; only two evaluated the concentration of organisms in faeces. The prevalence of faecal E. coli O157 shedding in cattle is significantly reduced by DFM treatments (summary effect size for all DFM - OR = 0.46; CI = 0.36-0.60). The DFM combination Lactobacillus acidophilus (NP51) and Propionibacterium freudenreichii (NP24) was more efficacious in reducing the prevalence of faecal E. coli O157 shedding at the time of harvest and throughout the trial period compared with the group of other DFM, although this difference was not statistically significant. Furthermore, we found that the combination [NP51 and NP24] treatment was more efficacious in reducing the prevalence of faecal E. coli O157 shedding at the time of harvest and throughout the trial period when fed at the dose of 10(9) CFU/animal/day than any lesser amount, although this difference was not statistically significant. Feeding beef cattle DFM during the pre-harvest stage of production reduces the prevalence of E. coli O157 faecal shedding and might effectively reduce human infections.
Topics: Animals; Antibiosis; Bacterial Shedding; Cattle; Escherichia coli Infections; Escherichia coli O157; Humans; Probiotics; Zoonoses
PubMed: 24751204
DOI: 10.1111/zph.12112