G T Macfarlane

University of Dundee, Dundee, Scotland, United Kingdom

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Publications (149)550.05 Total impact

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    ABSTRACT: Ageing can result in major changes in the composition and metabolic activities of bacterial populations in the large gut and an impaired immune system. To investigate the effects of synbiotic consumption on the colonic microbiota, immune function and health status in older people. A randomised, double-blind placebo-controlled, 4-week crossover study was carried out, involving 43 older volunteers, using a synbiotic comprising the probiotic Bifidobacterium longum and an inulin-based prebiotic Synergy 1 (SudZucker, Mannheim, Germany). Faecal and blood samples were collected, and clinical status scored at the start, and at 2- and 4-week intervals, with a 4-week washout between each feeding period. Faecal bacteria were determined by fluorescent in situ hybridisation. Short-chain fatty acid concentrations, cytokine production, bowel habit and a range of clinical parameters were measured. The synbiotic increased bifidobacterial numbers by 1.4 log units (P < 0.0001) and also increased members of the phyla Actinobacteria and Firmicutes (P = 0.0004, P < 0.0001). Proteobacteria were reduced by 1.0 log units (P < 0.0001). Synbiotic feeding was associated with increased butyrate production (P = 0.0399). The pro-inflammatory response was modified by the synbiotic, with significantly reduced pro-inflammatory cytokine TNF-α in peripheral blood after 2 and 4 weeks of synbiotic consumption (P = 0.02, P = 0.0406). The synbiotic had no effect on bowel habit or any clinical parameters. Short-term synbiotic use can be effective in improving the composition and metabolic activities of colonic bacterial communities and immune parameters in older people. This study was registered at clinicaltrials.gov as NCT01226212.
    Alimentary Pharmacology & Therapeutics 08/2013; · 4.55 Impact Factor
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    ABSTRACT: Barrett's oesophagus (BO) and gastro-oesophageal reflux disease (GERD) are precursors of oesophageal adenocarcinoma (OAC). There is an oesophageal biofilm, which changes in disease, but its role in aetiopathogenesis remains unclear. AIM: To define the oesophageal microbiota of patients with GERD, BO and OAC compared with controls and to investigate mucosal responses related to the microbiota. METHODS: Cultural analysis identified the dominant bacterial species from a subset of each disease group. Based on this, molecular techniques were used to define the cohort. Host responses were analysed in tissues and co-culture experiments. RESULTS: A total of 111 species belonging to 26 genera were isolated. There was a significant decrease in bacterial counts in the GERD and BO groups for all genera except Campylobacter, which colonised GERD and Barrett's patients in increasing numbers. Campylobacter concisus was the dominant species. This relationship was not seen in the cancer group. Significant increases in IL-18 were seen in GERD and BO colonised by Campylobacter. CONCLUSIONS: This study defines differences in the oesophageal biofilm in disease states, revealing the emergence of C. concisus as the dominant new colonist in the refluxed oesophagus. We also associate the presence of these bacteria with increased expression of cytokines related to carcinogenesis.
    Alimentary Pharmacology & Therapeutics 04/2013; · 4.55 Impact Factor
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    Dorothy F Newton, Sandra Macfarlane, George T Macfarlane
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    ABSTRACT: The composition and metabolic activities of the human colonic microbiota are modulated by a number of external factors, including diet and antibiotic therapy. Changes in the structure and metabolism of the gut microbiota may have long term consequences for host health. The large intestine harbors a complex microbial ecosystem comprising several hundreds of different bacterial species, which complicates investigations on intestinal physiology and ecology. To facilitate such studies, a highly simplified microbiota was used in this investigation consisting of 14 anaerobic and facultatively anaerobic organisms (Bacteroides thetaiotaomicron, B. vulgatus, Bifidobacterium longum, Bif. infantis, Bif. pseudolongum, Bif. adolescentis, Clostridium butyricum, C. perfringens, C. bifermentans, C. innocuum, Escherichia coli, Enterococcus faecalis, Ent. faecium, Lactobacillus acidophilus). Ampicillin (9.2 μg (mL culture)(-1)) was added to two chemostats operated at different dilution rates (D=0.10 h(-1) and D=0.21 h(-1)), and metronidazole (76.9 μg (mL culture)(-1)) to a third vessel (D=0.21 h(-1)). Perturbations in bacterial physiology and metabolism were sampled over a 48 hour period. Lactobacillus acidophilus and C. bifermentans populations did not establish in the fermentors, under the imposed growth conditions. Ampicillin resulted in substantial reductions in bacteroides and C. perfringens populations at both dilution rates. Metronidazole strongly affected bacteroides, but had no effect on bifidobacterial communities. The bacteriostatic effect of ampicillin on bifidobacterial species was growth rate-dependent. Several metabolic activities were affected by antibiotic addition, including fermentation product formation and enzyme synthesis. The growth of antibiotic-resistant bifidobacteria in the large bowel may enable them to occupy ecological niches left vacant post-antibiotic administration, preventing colonization by pathogenic species.
    Antimicrobial Agents and Chemotherapy 02/2013; · 4.57 Impact Factor
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    ABSTRACT: The majority of bacteria live not planktonically, but as residents of sessile biofilm communities. Such populations have been defined as 'matrix-enclosed microbial accretions, which adhere to both biological and nonbiological surfaces'. Bacterial formation of biofilm is implicated in many chronic disease states. Growth in this mode promotes survival by increasing community recalcitrance to clearance by host immune effectors and therapeutic antimicrobials. The human gastrointestinal (GI) tract encompasses a plethora of nutritional and physicochemical environments, many of which are ideal for biofilm formation and survival. However, little is known of the nature, function, and clinical relevance of these communities. This review summarizes current knowledge of the composition and association with health and disease of biofilm communities in the GI tract.
    Pathogens and disease. 02/2013; 67(1):25-38.
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    ABSTRACT: Bacteria belonging to the normal colonic microbiota are associated with the etiology of ulcerative colitis (UC). Although several mucosal species have been implicated in the disease process, the organisms and mechanisms involved are unknown. The aim of this investigation was to characterize mucosal biofilm communities over time, and to determine the relationship of these bacteria to disease severity and duration, and patient age. Multiple rectal biopsies were taken from 33 patients with active UC over a period of one year. Real-time PCR was used to quantify mucosal bacteria in UC compared to 18 non-inflammatory bowel disease controls, and the relationship between indicators of disease severity and bacterial colonization was evaluated by linear regression analysis. Significant differences were detected in bacterial populations on the UC mucosa and in the control group, which varied over the study period. High clinical activity indices (CAI) and sigmoidoscopy scores (SS) were associated with enterobacteria, desulfovibrios, Type E Clostridium perfringens and Enterococcus faecalis, whereas the reverse was true for Clostridium butyricum, Ruminococcus albus and Eubacterium rectale. Lactobacilli and bifidobacterial numbers were linked with low CAI. Only E. rectale and C. clostridioforme had a high age dependence. These findings demonstrated that longitudinal variations in mucosal bacterial populations occur in UC, and that bacterial community structure is related to disease severity.
    Journal of clinical microbiology 12/2012; · 4.23 Impact Factor
  • George T Macfarlane, Sandra Macfarlane
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    ABSTRACT: The colonic microbiota plays an important role in human digestive physiology and makes a significant contribution to homeostasis in the large bowel. The microbiome probably comprises thousands of different bacterial species. The principal metabolic activities of colonic microorganisms are associated with carbohydrate and protein digestion. Nutrients of dietary and host origin support the growth of intestinal organisms. Short-chain fatty acids (SCFAs), predominantly acetate, propionate, and butyrate, are the principal metabolites generated during the catabolism of carbohydrates and proteins. In contrast, protein digestion yields a greater diversity of end products, including SCFAs, amines, phenols, indoles, thiols, CO2, H2, and H2S, many of which have toxic properties. The majority of SCFAs are absorbed from the gut and metabolized in various body tissues, making a relatively small but significant contribution to the body's daily energy requirements. Carbohydrate fermentation is, for the most part, a beneficial process in the large gut, because the growth of saccharolytic bacteria stimulates their requirements for toxic products associated with putrefaction, for incorporation into cellular proteins, thereby protecting the host. However, as digestive materials move along the gut, carbohydrates become depleted, which may be linked to the increased prevalence of colonic disease in the distal bowel.
    Journal of AOAC International 01/2012; 95(1):50-60. · 1.39 Impact Factor
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    ABSTRACT: Patients with dysphagia require long-term nutritional support. This can be delivered by the enteral route via a percutaneous endoscopic gastrostomy (PEG) tube. Enteral nutrition (EN) bypasses the body's innate defences that prevent the microbial colonization of the proximal gut, which predisposes to microbial overgrowth. A continuous culture model simulating the upper gastrointestinal tract microbiota of EN patients was used to investigate the effects of a synbiotic (Lactobacillus acidophilus DUN-311, Bifidobacterium bifidum BB-02, Bifidobacterium lactis BL-01, Synergy 1) on microbial community structure and metabolism. A PEG tube was inserted into the fermenters to study biofilm formation. The synbiotic delivered in sterile semi-skimmed milk (SSSM) was introduced either 48 h prior to or after PEG tube insertion. The synbiotic reduced biofilm formation on PEG tube surfaces, with suppression of Escherichia coli and Klebsiella pneumoniae when it was added subsequent to PEG insertion. When synbiotic feeding was commenced prior to PEG insertion, colonization by Staphylococcus aureus, Candida albicans and Candida famata was also inhibited. Lactate production increased in response the synbiotic or control (SSSM). These results indicate that the use of a synbiotic has the potential to reduce pathogen colonization on PEG tube surfaces in vivo, thereby reducing the incidence of biofilm-related infectious complications.
    FEMS Microbiology Ecology 12/2011; 80(1):135-45. · 3.88 Impact Factor
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    ABSTRACT: Sepsis is common in liver cirrhosis, and animal studies have shown the gut to be the principal source of infection, through bacterial overgrowth and translocation in the small bowel. A total of 33 patients were recruited into this study, 10 without cirrhosis and 23 with cirrhotic liver disease. Six distal duodenal biopsies were obtained and snap frozen for RNA and DNA extraction, or frozen for FISH. Peripheral venous bloods were obtained from 30 patients, including 17 chronic liver disease patients. Samples were analysed by real-time PCR, to assess total bacteria, bifidobacteria, bacteroides, enterobacteria, staphylococci, streptococci, lactobacilli, enterococci, Helicobacter pylori and moraxella, as well as TNF-α, IL-8 and IL-18. There was no evidence of bacterial overgrowth with respect to any of the individual bacterial groups, with the exception of enterococci, which were present in higher numbers in cirrhotic patients (P = 0.04). There were no significant differences in any of the cytokines compared to the controls. The small intestinal mucosal microbiota in cirrhotic patients was qualitatively and quantitatively normal, and this shifts the focus of disease aetiology to factors that reduce gut integrity, failure of mechanisms to remove translocating bacteria, or the large bowel as the source of sepsis.
    FEMS Immunology & Medical Microbiology 12/2011; 63(3):346-54. · 2.68 Impact Factor
  • George T Macfarlane, Sandra Macfarlane
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    ABSTRACT: The human large intestine harbors a complex microbiota containing many hundreds of different bacterial species. Although structure/function relationships between different components of the microbiota are unclear, this complex multicellular entity plays an important role in maintaining homeostasis in the body. Many of the physiologic properties of the microbiota can be attributed to fermentation and the production of short-chain fatty acids (SCFAs), particularly acetate, propionate, and butyrate. In healthy people, fermentation processes are largely controlled by the amounts and different types of substrate, particularly complex carbohydrates that are accessible to bacteria in the colonic ecosystem. However, other factors impact on bacterial metabolism in the large gut, including large bowel transit time, the availability of inorganic terminal electron acceptors, such as nitrate and sulfate, and gut pH. They all affect the types and levels of SCFA that can be formed by the microbiota. This is important because to a large extent, acetate, propionate, and butyrate have varying physiologic effects in different body tissues. Prebiotics such as galactooligosaccharides together with inulins and their fructooligosaccharide derivatives have been shown to modify the species composition of the colonic microbiota, and in various degrees, to manifest several health-promoting properties related to enhanced mineral absorption, laxation, potential anticancer properties, lipid metabolism, and anti-inflammatory and other immune effects, including atopic disease. Many of these phenomena can be linked to their digestion and SCFA production by bacteria in the large gut.
    Journal of clinical gastroenterology 11/2011; 45 Suppl:S120-7. · 2.21 Impact Factor
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    ABSTRACT: This study describes the consensus opinion of the participants of the third Yale Workshop on probiotic use. There were 10 experts participating. The recommendations update those of the first 2 meetings that were published in 2005 and 2008. The workshop presentations and papers in this supplement relate to the involvement of normal microbiota involved in intestinal microecology, how the microbes interact with the intestine to affect our immunologic responses, the stability and natural history of probiotic organisms, and the role of the intestinal microbatome with regard to affecting cardiac risk factors and obesity. Recommendations for the use of probiotics in necrotizing enterocolitis, childhood diarrhea, inflammatory bowel disease, irritable bowel syndrome, and Clostridium difficile diarrhea are reviewed. As in previous publications, the recommendations are given as A, B, or C ratings. The recent positive experiences with bacteriotherapy (fecal microbiome transplant) are also discussed in detail and a positive recommendation is made for use in severe resistant C. difficile diarrhea.
    Journal of clinical gastroenterology 11/2011; 45 Suppl:S168-71. · 2.21 Impact Factor
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    ABSTRACT: IntroductionAn altered colonic microbiota contributes to inflammatory bowel disease (IBD) pathogenesis. Adult studies suggest modification of the microbiota by synbiotics (probiotics+prebiotics) can improve ulcerative colitis (UC)1 and Crohn's disease (CD)2.AimTo assess the feasibility of using a synbiotic in children with IBD.Methods Patients with IBD aged 6 to 16 years were approached. Children were excluded if they used any prebiotic/probiotic agent in the preceding 14 days, were using antibiotics or had a severe IBD exacerbation. Patients were withdrawn if they started antibiotics or another prebiotic/probiotic or they wished to discontinue. Participation involved taking the probiotic (Bifidobacterium longum in a capsule) and prebiotic (3.5 g Synergy 1 inulin oligofructose) twice daily for 12 weeks. A pre-study questionnaire and physician's global assessment (PGA) were completed. Questionnaires were provided for return at 1, 4, 8 and 12 weeks. Trial completion involved finishing the synbiotic course and returning all questionnaires.Results23 children were recruited. 11 (48%) were male. Median age was 13.4 years (7.8–16.6 years). 11 had CD, 6 UC and 4 IBD-unspecified. Initial PGA was ‘inactive’ in 19, ‘mild’ in 3, ‘moderate’ in 1 and ‘severe’ in 1. Only 3 of the first 17 patients completed the study. Feedback indicated the prebiotic was poorly tolerated, therefore the last six participants undertook a tapered probiotic course: none in week 1, once daily in week 2, then twice daily from week 3. Only two of six completed the modified study. Completion overall was 5/23 (22%). Reasons for withdrawal were: six diarrhoea/IBD flare, six stopped returning questionnaires, four required antibiotics, one advised by GP because of rash, one unwell on prebiotic but completed probiotic and one parent stopped after noticing ‘no difference.Conclusion Although synbiotics have shown promise in adult IBD this feasibility study in fairly well paediatric IBD patients has shown poor tolerability. We suspect the drop-out rate was due to the prebiotic agent, but further studies are necessary to assess the tolerance of different prebiotics/probiotics in paediatric IBD before larger efficacy trials.
    Archives of Disease in Childhood 04/2011; 96(1). · 2.91 Impact Factor
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    ABSTRACT: Adherence of bacteria to epithelial cells is an important step in colonization and immune modulation in the large bowel. The aims of this study were to use a three-stage continuous-culture system (CCS) to investigate how environmental factors affect bacterial attachment to Caco-2 cells and modulation of cytokine expression by gut microorganisms, including a probiotic Bifidobacterium longum strain, DD2004. The CCS simulated environmental conditions in the proximal large intestine (vessel 1 [V1]) and distal colon (V2 and V3) at two different system retention times (R) within the range of normal colonic transits (20 and 60 h). The model was inoculated with human fecal material, and fluorescence in situ hybridization (FISH) was used to characterize microbial populations and to assess bacterial attachment to Caco-2 cells. Real-time quantitative PCR (qPCR) was employed to measure cytokine gene expression following challenge with bacteria from different components of the CCS in the presence and absence of B. longum. At an R of 60 h, bacterial adherence increased from V1 to V3, but this trend was reversed at an R of 20 h. Atopobia were the predominant adherent organisms detected at both system retention times in each culture vessel. Modulation of transforming growth factor β1 (TGF-β1), interleukin 6 (IL-6), and IL-18 gene expression by CCS bacteria was marked at an R of 60 h, while at an R of 20 h, IL-4, IL-10, TGF-β2, IL-1α, and tumor necrosis factor alpha (TNF-α) were significantly affected. The addition of B. longum affected cytokine expression significantly at both retention times. This study demonstrates that environmental determinants regulate the adherence properties of intestinal bacteria and their abilities to regulate cytokine synthesis.
    Applied and Environmental Microbiology 03/2011; 77(9):2934-42. · 3.95 Impact Factor
  • Sandra Macfarlane, Bahram Bahrami, George T Macfarlane
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    ABSTRACT: Complex and highly variable site-dependent bacterial ecosystems exist throughout the length of the human gastrointestinal tract. Until relatively recently, the majority of our information on intestinal microbiotas has come from studies on feces, or from aspirates taken from the upper gut. However, there is evidence showing that mucosal bacteria growing in biofilms on surfaces lining the gut differ from luminal populations, and that due to their proximity to the epithelial surface, these organisms may be important in modulating the host's immune system and contributing to some chronic inflammatory diseases. Over the past decade, increasing interest in mucosal bacteria, coupled with advances in molecular approaches for assessing microbial diversity, has begun to provide some insight into the complexity of these mucosa-associated communities. In gastrointestinal conditions such as inflammatory bowel diseases (ulcerative colitis, Crohn's disease), it has been shown that a dysbiosis exists in microbial community structure, and that there is a reduction in putatively protective mucosal organisms such as bifidobacteria. Therefore, manipulation of mucosal communities may be beneficial in restoring normal functionality in the gut, thereby improving the immune status and general health of the host. Biofilm structure and function has been studied intensively in the oral cavity, and as a consequence, mucosal communities in the mouth will not be covered in this chapter. This review addresses our current knowledge of mucosal populations in the gastrointestinal tract, changes that can occur in community structure in disease, and therapeutic modulation of biofilm composition by antibiotics, prebiotics, and probiotics.
    Advances in applied microbiology 01/2011; 75:111-43. · 2.24 Impact Factor
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    ABSTRACT: Enteral feeding via a percutaneous endoscopic gastrostomy tube is required for nutritional support in patients with dysphagia. Enteral tube feeding bypasses the innate defence mechanisms in the upper gastrointestinal tract. This study examined the surface-associated microbial populations and immune response in the gastric and duodenal mucosae of eight enteral nutrition (EN) patients and ten controls. Real-time PCR and fluorescence in situ hybridization were employed to assess microbiota composition and mucosal pro-inflammatory cytokine expression. The results showed that EN patients had significantly higher levels of bacterial DNA in mucosal biopsies from the stomach and duodenum (P<0.05) than the controls, and that enterobacteria were the predominant colonizing species on mucosal surfaces in these individuals. Expression of the pro-inflammatory cytokines interleukin (IL)-1α, IL-6 and tumour necrosis factor-α was significantly higher in gastric and small intestinal mucosae from patients fed normal diets in comparison with those receiving EN (P<0.05). These results indicate that EN can lead to significant bacterial overgrowth on upper gastrointestinal tract mucosae and a significantly diminished pro-inflammatory cytokine response.
    Journal of Medical Microbiology 11/2010; 60(Pt 3):359-65. · 2.27 Impact Factor
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    B Bahrami, S Macfarlane, G T Macfarlane
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    ABSTRACT: To investigate the effects of human gut micro-organisms on cytokine production by human intestinal cell lines. Quantitative real-time PCR assays were developed to measure the production of pro-inflammatory (IL-1α, IL-6, IL-18 and TNFα) and anti-inflammatory (TGF-β1, TGF-β2, TGF-β3, IL-4 and IL-10) cytokines in HT-29 and Caco-2 cell lines. They were co-cultured with a range of mucosal bacteria isolated from ulcerative colitis patients, together with lactobacilli and bifidobacteria obtained from healthy people. HT-29 cells were also co-cultured with Campylobacter jejuni, enterotoxigenic Escherichia coli (ETEC), enteropathogenic E. coli and Salmonella typhimurium. The majority of commensal bacteria tested suppressed the expression of anti-inflammatory cytokine mRNA, increased IL-18, reduced IL-1α, and with the exception of nonpathogenic E. coli, reduced TNF-α. All overtly pathogenic species increased both pro-inflammatory and anti-inflammatory cytokine mRNA. Conclusion:  Commensal and pathogenic species induced fundamentally different cytokine responses in human intestinal epithelial cell lines. Interactions between commensal bacteria tested in this study and the innate immune system were shown to be anti-inflammatory in nature, in contrast to the pathogenic organisms investigated. These data contribute towards our understanding of how potential probiotic species can be used to suppress the pro-inflammatory response in inflammatory bowel disease.
    Journal of Applied Microbiology 10/2010; 110(1):353-63. · 2.39 Impact Factor
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    ABSTRACT: Crohn's disease is an inflammatory illness in which the immune response against gut microorganisms is believed to drive an abnormal immune response. Consequently, modification of mucosal bacterial communities, and the immune effects they elicit, might be used to modify the disease state. To investigate the effects of synbiotic consumption on disease processes in patients with Crohn's disease. A randomized, double-blind placebo-controlled trial was conducted involving 35 patients with active Crohn's disease, using a synbiotic comprising Bifidobacterium longum and Synergy 1. Clinical status was scored and rectal biopsies were collected at the start, and at 3- and 6-month intervals. Transcription levels of immune markers and mucosal bacterial 16S rRNA gene copy numbers were quantified using real-time PCR. Significant improvements in clinical outcomes occurred with synbiotic consumption, with reductions in both Crohn's disease activity indices (P = 0.020) and histological scores (P = 0.018). The synbiotic had little effect on mucosal IL-18, INF-gamma and IL-1beta; however, significant reductions occurred in TNF-alpha expression in synbiotic patients at 3 months (P = 0.041), although not at 6 months. Mucosal bifidobacteria proliferated in synbiotic patients. Synbiotic consumption was effective in improving clinical symptoms in patients with active Crohn's disease.
    Alimentary Pharmacology & Therapeutics 10/2010; 32(7):872-83. · 4.55 Impact Factor
  • Sandra Macfarlane, Helen Steed, George T Macfarlane
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    ABSTRACT: Crohn's disease (CD) and ulcerative colitis (UC) are the two principal forms of inflammatory bowel disease (IBD). Animal studies show that bacteria are involved in the etiology of IBD, and much is now known about the inflammatory processes associated with CD and UC, as well as the underlying genetic, environmental, and lifestyle issues that can affect an individual's predisposition to these diseases. However, while a number of candidate microorganisms have been put forward as causative factors in IBD, the primary etiologic agents are unknown. This review discusses the potential role of luminal and mucosal microbial communities in the etiology of IBD, and outlines studies that have been made using a variety of biotherapeutic therapies, involving the use of antibiotics, probiotics, prebiotics, and synbiotics.
    Critical Reviews in Clinical Laboratory Sciences 02/2009; 46(1):25-54. · 3.78 Impact Factor
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    ABSTRACT: Crohn's disease and ulcerative colitis are the two principal forms of inflammatory bowel disease (IBD). The root causes of these chronic and acute immunological disorders are unclear, but intestinal microorganisms are known to play a key role in the initiation and maintenance of disease. However, at present, there is no clear evidence for a single transmissible agent being involved in IBD aetiology. Although marked alterations occur in faecal and mucosal bacterial communities in IBD, it is unclear whether they are responsible for causing disease, or are due to changes in the gut environment that result from inflammatory reactions and extensive tissue destruction. Despite the involvement of microorganisms in inflammatory processes, antibiotic therapy has generally been unsuccessful in IBD. However, recent studies involving the use of probiotics, prebiotics and synbiotics suggest that there is potential for controlling these diseases through manipulation of the composition of the gut microbiota, and direct interactions with the gut immune system.
    Current pharmaceutical design 02/2009; 15(13):1528-36. · 4.41 Impact Factor
  • G T Macfarlane, L E Macfarlane
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    ABSTRACT: The gut is sterile at birth, but is rapidly colonised by faecal and vaginal bacteria of maternal origin. Over the succeeding weeks, months and years, a complex microbiota develops that plays a major role in host physiology. While the digestive tract is colonised to varying degrees by micro-organisms throughout its length, due to acid pH and the short retention time of gastric contents, bacterial numbers in the stomach are usually low. The rapid passage of digestive materials through the upper gut does not provide time for significant bacterial growth to occur, but cell numbers increase considerably in the distal ileum. The rate of movement of intestinal contents slows in the colon, which facilitates the development of complex bacterial communities. The large intestine is an intricate ecosystem that contains a complex microbiota composed of several hundred different types of bacteria. The growth and metabolism of microbial communities in the large intestine are determined by many factors, such as diet, environment and host physiological processes, as well as the anatomic structure of the digestive tract, disease, immunity, host genetics, drugs and ageing. Modifications in diet and host immune system activity, as well as physiological changes in the digestive tract affect microbiota composition in older people. The elderly have fewer bifidobacteria and higher numbers of enterobacteria and clostridia than young adults. Increased antibiotic use in older people and simply going into hospital have been shown to change bacterial community structure in the colonic microbiota, although the metabolic significance of this is unclear.
    Digestive Diseases 01/2009; 27 Suppl 1:90-8. · 2.73 Impact Factor
  • Gut 01/2009; 58:A68-A69. · 13.32 Impact Factor

Publication Stats

8k Citations
550.05 Total Impact Points


  • 2000–2013
    • University of Dundee
      • Division of Neuroscience
      Dundee, Scotland, United Kingdom
  • 2005–2010
    • Ninewells Hospital
      Dundee, Scotland, United Kingdom
  • 2007
    • University of Cape Town
      • Division of Cell Biology
      Cape Town, Province of the Western Cape, South Africa
  • 2001–2007
    • The University of Manchester
      • School of Pharmacy and Pharmaceutical Sciences
      Manchester, England, United Kingdom
  • 2000–2001
    • London South Bank University
      • Department of Applied Science
      London, ENG, United Kingdom
  • 1987–1998
    • MRC Clinical Sciences Centre
      London Borough of Harrow, England, United Kingdom
  • 1992–1996
    • University of Cambridge
      Cambridge, England, United Kingdom
  • 1994
    • Newcastle University
      Newcastle-on-Tyne, England, United Kingdom