Biomedical subjects

G R Gibson

Publications and source records attributed to G R Gibson.

At least 37 records · Page 2Linked to original sources

PubMed2002

Comparison of the in vitro bifidogenic properties of pectins and pectic-oligosaccharides.

AIMS: To compare the in vitro fermentation properties of pectins and oligosaccharides derived from them in pure and mixed faecal cultures. METHODS AND RESULTS: Specific growth rates of selected bacterial genera were calculated in pure culture. Bifidobacterium angulatum, B. infantis and B. adolescentis had higher growth rates on pectic oligosaccharides (POS I) derived from high methylated pectin (HMP) than on HMP and B. pseudolongum and B. adolescentis on pectic oligosaccharides (POS II) derived from low methylated pectin than on HMP. Controlled pH batch mixed faecal cultures were then carried out and a prebiotic index was calculated as a mean to compare the fermentation properties of the different substrates. In general, greater fermentation selectivity was obtained with lower degrees of methylation (PI24(-HMP) = -0.11, PI24(-LMP) = 0.033; PI24(-POS I) = 0.071 and PI24(-POS II) = 0.092). An effect of size on prebiotic potential was observed, with the oligosaccharides having more selective fermentation properties than the pectins they derived from. CONCLUSIONS: The degree of methylation plays an important role in the fermentation properties of pectins. Pectic-oligosaccharides are a better prebiotic candidate than the pectins, although their bifidogenic effect is low compared to oligofructose. SIGNIFICANCE AND IMPACT OF THE STUDY: The effect of size on prebiotic potential was demonstrated. Non-selectively fermented polysaccharides like pectin can have their bifidogenic properties improved by partial hydrolysis.

Bacteria↗

PubMed2002

Bacteriology of the Labrador dog gut: a cultural and genotypic approach.

AIMS: To carry out an extensive study of the microflora composition of the Labrador dog gut. METHODS AND RESULTS: Faecal specimens from four Labradors were collected and plated onto growth media designed to recover total anaerobes, bacteroides, bifidobacteria, lactobacilli, clostridia, Gram-positive cocci, total aerobes and coliforms. Morphologically different isolates were collected from all agars inoculated with faeces from one canine individual (repeated four times). A total of 157 out of 171 isolates were identified using 16S rRNA gene sequencing. Sequence analysis showed that agar selectivity was poor, especially when bacteroides and Gram-positive cocci were the targets. Bifidobacteria were not detected in any of the samples analysed, indicating their presence at low or negligible levels. The gene sequences of many of the isolates (n=45, representing 29% of the total) did not correlate with known species in the Ribosomal Database Project and EMBL databases, suggesting the presence of novel gut diversity. CONCLUSIONS: Traditional culture methods fail to reflect the bacterial diversity present in Labrador dog faeces. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has shown the value of molecular-based methodologies for determining bacterial profiles in the Labrador dog gut microbiota, but has also exposed the limitations of purportedly selective agars.

Animals↗

PubMed2002

Investigating the prebiotic and gas-generating effects of selected carbohydrates on the human colonic microflora.

AIMS: To compare the fermentation of dietary carbohydrates with reference to their prebiotic and gas-generating capacity. METHODS AND RESULTS: Static anaerobic batch culture fermentations were carried out measuring gas generation and the prebiotic effect of five selected substrates (including various fructo-oligosaccharides, levan and maltodextrin). The largest gas producer was levan, whilst those showing no significant difference to Actilight included oligofructose and maltodextrin. Gas composition data showed that hydrogen and carbon dioxide were the two most quantitatively important gases. The substrate that appeared to have the best prebiotic effect in vitro was branched chain fructo-oligosaccharide (FOS), followed by oligofructose, Actilight and maltodextrin which each exerted a similar effect. The substrate with the least bifidogenic effect was levan. CONCLUSIONS: The composition and total gas generation data showed that there was much variation between and within donor inocula. Generally, the lower gas producers had a more selective fermentation whilst larger gas producers were less specific. SIGNIFICANCE AND IMPACT OF THE STUDY: The study of these three parameters enabled a more complete picture of carbohydrate breakdown to be drawn and hence highlighted the need for potential prebiotics to be more extensively evaluated in order to reduce negative side-effects such as gas distension.

Bacteria↗

PubMed2002

Probiotics as modulators of the gut flora.

Probiotic ingestion can be recommended as a preventative approach to maintaining the balance of the intestinal microflora and thereby enhance 'well-being'. Research into the use of probiotic intervention in specific illnesses and disorders has identified certain patient populations that may benefit from the approach. Undoubtedly, probiotics will vary in their efficacy and it may not be the case that the same results occur with all species. Those that prove most efficient will likely be strains that are robust enough to survive the harsh physico-chemical conditions present in the gastrointestinal tract. This includes gastric acid, bile secretions and competition with the resident microflora. A survey of the literature indicates positive results in over fifty human trials, with prevention/treatment of infections the most frequently reported output. In theory, increased levels of probiotics may induce a 'barrier' influence against common pathogens. Mechanisms of effect are likely to include the excretion of acids (lactate, acetate), competition for nutrients and gut receptor sites, immunomodulation and the formation of specific antimicrobial agents. As such, persons susceptible to diarrhoeal infections may benefit greatly from probiotic intake. On a more chronic basis, it has been suggested that some probiotics can help maintain remission in the inflammatory conditions, ulcerative colitis and pouchitis. They have also been suggested to repress enzymes responsible for genotoxin formation. Moreover, studies have suggested that probiotics are as effective as anti-spasmodic drugs in the alleviation of irritable bowel syndrome. The approach of modulating the gut flora for improved health has much relevance for the management of those with acute and chronic gut disorders. Other target groups could include those susceptible to nosocomial infections, as well as the elderly, who have an altered microflora, with a decreased number of beneficial microbial species. For the future, it is imperative that mechanistic interactions involved in probiotic supplementation be identified. Moreover, the survival issues associated with their establishment in the competitive gut ecosystem should be addressed. Here, the use of prebiotics in association with useful probiotics may be a worthwhile approach. A prebiotic is a dietary carbohydrate selectively metabolised by probiotics. Combinations of probiotics and prebiotics are known as synbiotics.

Animals↗

PubMed2002

Prebiotic effects of inulin and oligofructose.

Prebiotics are non-digestible food ingredients that target certain components within the microbiota of the human large intestine. Efficient prebiotics need to have a specific fermentation therein and thereby have the ability to alter the faecal microflora composition towards a more 'beneficial' community structure. This should occur by the stimulation of benign or potentially health promoting genera but not the harmful groups. Because of their positive attributes bifidobacteria and lactobacilli are the most frequent target organisms. Both inulin and oligofructose have been demonstrated to be effective prebiotics. This has been shown through both in vitro and in vivo assessments in different laboratories. Because of their recognised prebiotic properties, principally the selective stimulation of colonic bifidobacteria, both inulin and oligofructose are increasingly used in new food product developments. Examples include drinks, yoghurts, biscuits and table spreads. Because of the recognised inhibitory effects that bifidobacteria can exert against gut pathogens, one of the most important aspects of prebiotic ingestion is fortification of the gut flora to resist acute infections.

Bifidobacterium↗

PubMed2002

Bacterial biofilms in the human gastrointestinal tract.

Microbial biofilms were first described in 1936 and subsequent research has unveiled their ubiquity and physiological distinction from free-living (planktonic) microorganisms. In light of their emerging significance this review examines the bacterial biofilms within the human gastrointestinal tract. Attention is paid to the nature of these mucosally- associated populations, focusing on the protected environment afforded by the continual secretion of mucus by host epithelial cells. It also examines the attributes possessed by various bacterial species that facilitate habitation of this microenvironment. Additionally, contrasts are drawn between planktonic bacteria of the lumen and sessile (biofilm) bacteria growing in close association with host cells and food particles. In particular the different fermentation profiles exhibited by these two fractions are discussed. The potential role of these communities in host health and disease, as well as the stabilisation of the lumenal population, is also considered. Reference is made to the state of mutualism that exists between these little understood populations and the host epithelia, thus highlighting their ecological significance in terms of gastrointestinal health.

Bacterial Physiological Phenomena↗

PubMed2001

Intranodal immunization with tumor lysate-pulsed dendritic cells enhances protective antitumor immunity.

We developed a technique for direct inguinal lymph node injection in mice to compare various routes of immunization with tumor lysate-pulsed dendritic cell (DC) vaccines. Syngeneic, bone marrow-derived, tumor lysate-pulsed DCs administered intranodally generated more potent protective antitumor immunity than s.c. or i.v. DC immunizations. Intranodal immunization with ovalbumin peptide-pulsed DCs induced significantly greater antigen-specific T-lymphocyte expansion in the spleen than either s.c. or i.v. immunization. Furthermore, a significantly more potent, antigen-specific TH1-type response to the ovalbumin peptide was induced by intranodal, compared with s.c. or i.v., immunization. Intranodal immunization, designed to enhance DC-T cell interaction in a lymphoid environment, optimizes induction of T lymphocyte-mediated protective antitumor immunity. These results support the use of intranodal immunization as a feasible and effective route of DC vaccine administration.

Animals↗

PubMed2001

A comparison of ink-directed and traditional whole-cavity re-excision for breast lumpectomy specimens with positive margins.

BACKGROUND: Excising a breast tumor with negative margins minimizes local recurrence. With a positive margin, the standard re-excision consists of excising the whole cavity and all surrounding breast tissue. By marking the sides of the lumpectomy specimen with six different colored inks, the surgeon can limit the re-excision to the involved margin. We compared the local recurrence rate after these two re-excision methods. METHODS: Records were reviewed of 527 women (546 breasts) treated with lumpectomy at two institutions. The log-rank test was used to compare the local recurrence-free survival. RESULTS: Of 546 tumors, 245 (45%) had negative margins on the initial lumpectomy and were not re-excised. Fifty-five percent had a positive or close margin; 181 underwent whole-cavity re-excision, and 120 had ink-directed re-excision. The mean follow-up time was 3.4 years. There was no significant difference in local recurrence for the patients whose initial margin was negative (3.7%) compared with the 243 patients with initially positive margins who underwent a re-excision (3.3%). Eleven of 181 (6%) patients undergoing a whole-cavity re-excision developed a local recurrence, compared with none of 120 (0%) patients with an ink-directed re-excision (P = not significant). Tissue mass excised was significantly smaller in the ink-directed group (23 vs. 83 g, P < .05). CONCLUSIONS: Ink-directed re-excision of lumpectomy specimens with positive margins minimizes the amount of breast tissue removed without increasing the incidence of local recurrence and is therefore preferable to the standard whole-cavity method.

Breast Neoplasms↗

PubMed2001

Isolation and characterization of human colonic bacteria able to hydrolyse chlorogenic acid.

AIMS: Conjugated hydroxycinnamates, such as chlorogenic acid (caffeoyl-quinic acid), are widely consumed in a Western diet, coffee being one of the richest sources. Ingested hydroxycinnamate esters can reach the large intestine essentially unaltered, and may then be hydrolysed by esterases produced by the indigenous microflora. This study is aimed at identifying bacterial species responsible for the release of natural antioxidants, such as hydroxycinnamic acids, in the human large intestine. METHODS AND RESULTS: Thirty-five isolates recovered after anaerobic batch culture incubation of human faecal bacteria in a chlorogenic acid-based medium were screened for cinnamoyl esterase activity. Six isolates released the hydroxycinnamate, ferulic acid, from its ethyl ester in a plate-screening assay, and these were identified through genotypic characterization (16S rRNA sequencing) as Escherichia coli (three isolates), Bifidobacterium lactis and Lactobacillus gasseri (two strains). Chlorogenic acid hydrolysing activities were essentially intracellular. These cinnamoyl esterase-producing organisms were devoid of other phenolic-degrading activities. CONCLUSION: The results show that certain gut bacteria, including some already recognized as potentially health-promoting (i.e. species belonging to the genera Bifidobacterium and Lactobacillus), are involved in the release of bioactive hydroxycinnamic acids in the human colon. SIGNIFICANCE AND IMPACT OF THE STUDY: Free hydroxycinnamates, including caffeic, ferulic and p-coumaric acids, exhibit antioxidant and anticarcinogenic properties both in vitro and in animal models. Given that the gut flora has a major role in human nutrition and health, some of the beneficial effects of phenolic acids may be ascribed to the microflora involved in metabolism.

Adult↗

PubMed2001

A comparative in vitro evaluation of the fermentation properties of prebiotic oligosaccharides.

AIMS: Comparison of in vitro fermentation properties of commercial prebiotic oligosaccharides. METHODS AND RESULTS: Populations of predominant gut bacterial groups were monitored over 24 h of batch culture through fluorescent in-situ hybridization. Short-chain fatty acid and gas production were also measured. All prebiotics increased the numbers of bifidobacteria and most decreased clostridia. Xylo-oligosaccharides and lactulose produced the highest increases in numbers of bifidobacteria whilst fructo-oligosaccharides produced the highest populations of lactobacilli. Galacto-oligosaccharides (GOS) resulted in the largest decreases in numbers of clostridia. Short-chain fatty acid generation was highest on lactulose and GOS. Gas production was lowest on isomalto-oligosaccharides and highest on inulin. CONCLUSIONS: The oligosaccharides differed in their fermentation characteristics. Isomalto-oligosaccharides and GOS were effective at increasing numbers of bifidobacteria and lactate whilst generating the least gas. SIGNIFICANCE AND IMPACT OF THE STUDY: The study provides comparative data on the properties of commercial prebiotics, allowing targeting of dietary intervention for particular applications and blending of oligosaccharides to enhance overall functionality.

Bacteria↗

PubMed2001

The role of probiotics and prebiotics in the management of diarrhoea associated with enteral tube feeding.

INTRODUCTION: Diarrhoea is a common and serious complication of enteral tube feeding, and has a range of aetiologies. Manipulation of the colonic microflora may reduce the incidence of enteral tube feeding diarrhoea via suppression of enteropathogens and production of short-chain fatty acids. Probiotics and prebiotics are commonly used during enteral tube feeding to manipulate the colonic microflora; however, their efficacy is as yet uncertain. METHODS: English-language studies investigating the pathogenesis of enteral tube feeding diarrhoea and the use of probiotics and prebiotics were identified by searching the electronic databases CINAHL, EMBASE and MEDLINE from 1980 to 2001. The bibliographies of articles obtained were searched manually. RESULTS: Only two prospective, randomized, double-blind, placebo-controlled trials have investigated the effect of a probiotic on enteral tube feeding diarrhoea; however, results are conflicting. No prospective, randomized, double-blind, placebo-controlled studies have specifically addressed the effect of a prebiotic on the incidence of enteral tube feeding diarrhoea. CONCLUSION: Theoretically, probiotics and prebiotics may be of benefit in prophylaxis against enteral tube feeding diarrhoea; however, there is currently insufficient evidence to support their routine use. Prospective, randomised, double-blind, placebo-controlled studies investigating their effect on diarrhoea are required. These observations are discussed with reference to the current literature.

Diarrhea↗

PubMed2001

Fermentation properties of gentio-oligosaccharides.

AIMS: To investigate the fermentation properties of gentio-oligosaccharides (GOS), as compared to fructo-oligosaccharides (FOS) and maltodextrin in mixed faecal culture. METHODS AND RESULTS: The substrates were incubated in 24 h batch culture fermentations of human faecal bacteria. Fluorescent in situ hybridization was used to determine changes in populations of bifidobacteria, lactobacilli, clostridia, bacteroides, streptococci and Escherichia coli. Gas and short-chain fatty acid (SCFA) production was also measured. GOS gave the largest significant increases in bifidobacteria, lactobacilli and total bacterial numbers during the incubations. However, FOS appeared to be a more selective prebiotic as it did not significantly stimulate growth of bacterial groups which were not probiotic in nature. GOS and maltodextrin produced the highest levels of SCFA. Lowest gas production was seen with GOS and highest with FOS. CONCLUSIONS: GOS possessed bifidogenic activity in vitro. Although fermentation of GOS was not as selective as FOS, gas production was lower. Gas production is often seen as an undesirable side effect of prebiotic consumption. SIGNIFICANCE AND IMPACT OF THE STUDY: The study has provided the first data on fermentation of GOS in mixed faecal culture. The study has also used molecular microbiology methods (FISH) to quantify bacterial groups. The data extend our knowledge of the selectivity of fermentation of oligosaccharides by the gut microflora.

Bacteria↗

PubMed2001

Clostridium hathewayi sp. nov., from human faeces.

A strictly anoxic, Gram-positive, sporeforming, rod-shaped bacterium was isolated from a chemostat inoculated with human faeces. The bacterium used carbohydrate as fermentable substrates, producing acetate, ethanol, carbon dioxide and hydrogen as the major products of glucose metabolism, and possessed a G + C content of 50.7 to 50.9 mol%. Comparative 16S rRNA gene sequencing showed that the unidentified bacterium represents a previously unrecognised sub-line within the Clostridium coccoides rRNA group of organisms. The nearest relatives of the unknown bacterium corresponded to Clostridium algidixylanolyticum, C. aerotolerans, C. celerecrescens, C. indolis, C. sphenoides, C. methoxybenzovorans and C. xylanolyticum but 16S rRNA sequence divergence values of >4% demonstrated that it represents a novel species. Based on the presented findings a new species, Clostridium hathewayi, is described. The type strain of Clostridium hathewayi is DSM = 13479T (= CCUG 43506 T).

Clostridium↗

PubMed2001

The prebiotic effects of biscuits containing partially hydrolysed guar gum and fructo-oligosaccharides--a human volunteer study.

Prebiotics are non-digestible food ingredients that target selected groups of the human colonic microflora, thus having the ability to alter the composition towards a more 'beneficial' community, i.e. selectively increasing populations of bifidobacteria and/or lactobacilli. In the present study the prebiotic potential of partially hydrolysed guar gum (PHGG) and fructo-oligosaccharides (FOS) in a biscuit was assessed in human volunteers. Fluorescent in situ hybridization using oligonucleotide probes targeting Bacteroides spp., Bifidobacterium spp., Clostridium spp. and Lactobacillus-Enterococcus spp. were used for the bacteriology and total bacteria were enumerated using the fluorescent stain 4',6-diamidino-2-phenylindole. Thirty-one volunteers consumed daily either three experimental biscuits (providing a total (g/d) of 6.6 FOS and 3.4 PHGG) or three placebo biscuits for two 21-d crossover periods. Bifidobacteria significantly increased in number on ingestion of the experimental biscuits compared with pre-treatment and placebo population levels. Bifidobacterial numbers returned to pretreatment levels within 7 d of the cessation of intake of experimental biscuits. A correlation was observed between the initial faecal bifidobacterial numbers and the magnitude of bifidogenesis, with volunteers who possessed low initial population levels of bifidobacteria experiencing the greatest increase in bifidogenesis. No changes were observed in the other bacterial groups monitored during the trial. Thus, the prebiotic nature of FOS and PHGG was maintained in a final food product as evidenced from the selective increase in bifidobacterial numbers.

Adult↗

PubMed2001

Characterizing the composition of intestinal microflora as a prospective treatment target in infant allergic disease.

We assessed the fecal microflora of 10 healthy infants and 27 infants with atopic eczema during breast-feeding and after weaning. The atopic infants had less frequently Gram-positive species among the most predominant aerobes and smaller total cell counts. Further differences were associated with more extensive manifestations, seen as higher bacteroides and lower bifidobacteria counts. Weaning resulted in decreased bacteroides counts in atopic and total cell counts in healthy infants and diminished predominance by bifidobacteria in both. In conclusion, the most prominent question raised by these data is whether Gram-positive bacteria may have distinctive importance in protection against atopic sensitization. Further studies aiming to answer this question are warranted.

Animals↗

PubMed2001

Differences in the gut bacterial flora of healthy and milk-hypersensitive adults, as measured by fluorescence in situ hybridization.

We enumerated the predominant gut genera from fecal samples of nine healthy and eight milk-hypersensitive adults both before and after 4 weeks Lactobacillus rhamnosus GG (LGG) supplementation. The anaerobic intestinal microflora of milk-hypersensitive adults was found to resemble that of healthy adults. LGG-consumption resulted in a significant increase in the number of bifidobacteria in healthy but not in milk-hypersensitive subjects, as well as a general increase in bacterial numbers in all other bacterial genera tested in both groups. In conclusion, the composition of the gut microbiota in milk-hypersensitive adults appears to be normal. LGG may have potential in reinforcing the endogenous flora.

Adult↗

PubMed2001

Synthesis and fermentation properties of novel galacto-oligosaccharides by beta-galactosidases from Bifidobacterium species.

beta-Galactosidase enzymes were extracted from pure cultures of Bifidobacterium angulatum, B. bifidum BB-12, B. adolescentis ANB-7, B. infantis DSM-20088, and B. pseudolongum DSM-20099 and used in glycosyl transfer reactions to synthesize oligosaccharides from lactose. At a lactose concentration of 30% (wt/wt) oligosaccharide yields of 24.7 to 47.6% occurred within 7 h. Examination of the products by thin-layer chromatography and methylation analysis revealed distinct product derived spectra from each enzyme. These were found to be different to that of Oligomate 55, a commercial prebiotic galacto-oligosaccharide. Fermentation testing of the oligosaccharides showed an increase in growth rate, compared to Oligomate 55, with products derived from B. angulatum, B. bifidum, B. infantis, and B. pseudolongum. However B. adolescentis had a lower growth rates on its oligosaccharide compared with Oligomate 55. Mixed culture testing of the B. bifidum BS-4 oligosaccharide showed that the overall prebiotic effect was equivalent to that of Oligomate 55.

Bifidobacterium↗

PubMed2000

Comparison of viable cell counts and fluorescence in situ hybridization using specific rRNA-based probes for the quantification of human fecal bacteria.

Conventional cultivation and fluorescence in situ hybridization (FISH) using 16S rRNA-based probes were compared for the enumeration of human colonic bacteria. Groups of common intestinal anaerobic bacteria were enumerated in slurries prepared from fecal samples of three healthy volunteers. To introduce variation between the samples, they were incubated for 48 h in batch culture (anaerobic) fermenters at 37 degrees C, and pure cultures of Bifidobacterium infantis, Clostridium perfringens, or Lactobacillus acidophilus were added. Samples were taken from the fermenters at different times. Total anaerobes, bifidobacteria, bacteroides, clostridia, and lactobacilli were enumerated by both plating and FISH. The results showed that plate counts of total anaerobes, bifidobacteria, lactobacilli and bacteroides were approximately ten-fold lower than the corresponding FISH counts. Numbers of clostridia were higher using the plating method, probably because the clostridia probe used in FISH analyses was designed to only detect part of the genus Clostridium. The introduced variation in the methods could be detected by both methods and was comparable.

Adult↗