Microbial Ecology of the Gastrointestinal Tract

Savage, Dwayne C.

doi:10.1146/annurev.mi.31.100177.000543

Cited by 2,119 publications

(1,336 citation statements)

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“…It is, however, questionable whether an ingested dose of lactic acid bacteria in the range of 10 10 ± 11 bacteria is able to in¯uence the colonic¯ora, which number approximately 10 13 bacteria (10 11 g), a number of 100 ± 1000 times higher than the ingested amount of lactic acid bacteria. This question is even more pertinent in light of the widely held belief that a dietary culture, even one possessing in vitro adhering capabilities, is highly unlikely to displace any bacterial strain that colonises a healthy human intestinal tract (Savage, 1977). Human gastrointestinal microbiology is notably a dif®cult ®eld to study because of limits on direct experimentation and the dif®cult physiological requirements of the intestinal microbes.…”

Section: Prevention Of Colonic Cancermentioning

confidence: 99%

Lactic acid bacteria and the human gastrointestinal tract

1999

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Objective: This review summarises the effects of lactic acid bacteria on lactose malabsorption, bacterialaviral or antibiotic associated diarrhoea, and describes the impact of lactic acid bacteria on cancer and the fermentative products in the colon. Results: Eight studies (including 78 patients) demonstrated that lactase de®cient subjects absorbed lactose in yogurt better than lactose in milk, while two studies (25 patients) did not support this. Two studies (22 patients) showed that unfermented acidophilus milk was absorbed better than milk, while six studies (68 patients) found no signi®cant differences. Addition of lactose hydrolysing enzyme, lactase, to milk improved lactose malabsorption in seven studies (131 lactose malabsorbers), while one study (10 malabsorbers) demonstrated no improvement. Lactic acid bacteria alleviated travellers' diarrhoea in one study (94 individuals) while a study including 756 individuals was borderline statistically signi®cant. One study (50 individuals) did not ®nd an effect of lactic acid bacteria on travellers' diarrhoea. Six studies (404 infants) demonstrated a signi®cant effect of lactic acid bacteria on infant diarrhoea, while one study (40 infants) did not. Lactic acid bacteria moderated antibiotic associated diarrhoea in three studies (66 individuals), while two studies (117 individuals) were insigni®cant. Conclusions: Lactase de®cient subjects bene®t from a better lactose absorption after ingestion of yoghurt compared with milk and from milk added lactase, whereas ingestion of unfermented acidophilus milk does not seem to improve lactose absorption. The majority of studies support that lactic acid bacteria alleviate bacterialaviral induced diarrhoea, especially in infants, while the effect on antibiotic associated diarrhoea is less clear.Experimental studies indicate an effect of lactic bacteria on human cell cancer lines, but clinical evidence is lacking. A`stabilising' effect of lactic acid bacteria on the colonic¯ora has not been documented.

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Section: Prevention Of Colonic Cancermentioning

confidence: 99%

Lactic acid bacteria and the human gastrointestinal tract

1999

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“…Many of these studies have focused on the microbiota of the gut. Analysis of the fecal microbiota can provide information about, for example, the host’s metabolism, health status and/or dietary intake [1–3]. …”

Section: Introductionmentioning

confidence: 99%

Evaluation and optimization of microbial DNA extraction from fecal samples of wild Antarctic bird species

Eriksson

Mourkas

González‐Acuña

et al. 2017

Infection Ecology & Epidemiology

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Introduction: Advances in the development of nucleic acid-based methods have dramatically facilitated studies of host–microbial interactions. Fecal DNA analysis can provide information about the host’s microbiota and gastrointestinal pathogen burden. Numerous studies have been conducted in mammals, yet birds are less well studied. Avian fecal DNA extraction has proved challenging, partly due to the mixture of fecal and urinary excretions and the deficiency of optimized protocols. This study presents an evaluation of the performance in avian fecal DNA extraction of six commercial kits from different bird species, focusing on penguins. Material and methods: Six DNA extraction kits were first tested according to the manufacturers’ instructions using mallard feces. The kit giving the highest DNA yield was selected for further optimization and evaluation using Antarctic bird feces. Results: Penguin feces constitute a challenging sample type: most of the DNA extraction kits failed to yield acceptable amounts of DNA. The QIAamp cador Pathogen kit (Qiagen) performed the best in the initial investigation. Further optimization of the protocol resulted in good yields of high-quality DNA from seven bird species of different avian orders. Conclusion: This study presents an optimized approach to DNA extraction from challenging avian fecal samples.

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“…Specific microbial components have been shown to stimulate TCRa/b þ IEL in vivo, including indigenous gut bacteria [14][15][16]. However, because the load and composition of the microflora in the gut vary at different gut levels [17], its influence on the IEL population may also differ. This possibility is supported by recent studies that demonstrated regional phenotypic and functional specialization of intestinal IEL based on comparison between the murine large and small intestine [18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Regional Phenotypic Specialization of Intraepithelial Lymphocytes in the Rat Intestine Does Not Depend on Microbial Colonization

et al. 1997

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Helgeland L, Vaage JT, Rolstad B, Halstensen TS, Midtvedt T, Brandtzaeg P. Regional phenotypic specialization of intraepithelial lymphocytes in the rat intestine does not depend on microbial colonization. Scand J Immunol 1997;46:349-357 Recent studies in mice and humans have provided evidence for regional specialization of gut intraepithelial lymphocytes (IEL). Here the authors report striking regional variability in the composition of IEL in rat small and large intestine. Two-colour immunofluorescence in situ analysis showed that the distribution of the CD3 þ and CD3 ¹ IEL subpopulations varied, the proportion of T cells (CD3 þ ) being higher in the ileum than in the jejunum and smallest in the colon. These differences were explained by variable numbers of the T-cell receptor (TCR)a/b þ (both CD8 þ and CD4 þ ) but not the TCRg/d þ subset. Moreover, the various IEL subpopulations showed distinct intraepithelial distribution patterns with CD4 þ and CD8ab þ T cells situated near the lamina propria, while CD3 ¹ IEL were located preferentially towards the adluminal part of the epithelium. Regional phenotypic variation did not depend on intestinal colonization because analogous results were obtained in germ-free rats. Conventionalization nevertheless caused a marked relative increase of small intestinal TCRa/b þ but not TCRg/d þ IEL. This increase was more sustained in the jejunum than ileum and eventually reduced the phenotypic IEL differences between the two sites. By contrast, microbial colonization of the colon induced only a transient increase of intraepithelial TCRa/b þ cells with no permanent phenotypic alterations. Both CD3 þ and CD3 ¹ IEL contained subpopulations that expressed NKR-P1 independent of intestinal colonization. These results demonstrate phenotypic specialization of IEL at different levels of the gut and suggest that the indigenous flora is not essential to this end.

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Microbial Ecology of the Gastrointestinal Tract

Cited by 2,119 publications

References 1 publication

Lactic acid bacteria and the human gastrointestinal tract

Lactic acid bacteria and the human gastrointestinal tract

Evaluation and optimization of microbial DNA extraction from fecal samples of wild Antarctic bird species

Regional Phenotypic Specialization of Intraepithelial Lymphocytes in the Rat Intestine Does Not Depend on Microbial Colonization

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