Intestines flora

Intestinal flora is a general term for the bacteria yeast and fungi that live in the large intestine... 

Some vitamin K is provided m the normal diet but a large proportion of that required by humans is produced by their intestinal flora... 

Animals caimot synthesize the naphthoquinone ring of vitamin K, but necessary quantities are obtained by ingestion and from manufacture by intestinal flora. In plants and bacteria, the desired naphthoquinone ring is synthesized from 2-oxoglutaric acid (12) and shikimic acid (13) (71,72). Chorismic acid (14) reacts with a putative succinic semialdehyde TPP anion to form o-succinyl benzoic acid (73,74). In a second step, ortho-succmY benzoic acid is converted to the key intermediate, l,4-dihydroxy-2-naphthoic acid. Prenylation with phytyl pyrophosphate is followed by decarboxylation and methylation to complete the biosynthesis (75). 

Many azo dyes, such as tartrazine (Section 4.04.4.1.3), are susceptible to reduction by bacterial reductases in the intestinal flora. Azo reduction is believed to proceed through a hydrazo intermediate that undergoes subsequent reductive cleavage of the nitrogen-nitrogen bond to yield the arylamine derivatives (B-80MI40406). 

N. Roland, L. Nugon-Baudon and S. Rabot, in Intestinal Flora, Immunity Nutrition and Health, ed. A. P. Siinopoulos, T. Con ing and A. Rerat, World Reviews of Nutrition and Dietetics, Karger, Basel, 1993, vol. 74, pp. 123-148. 

Not all of the starch in a food ends up being digested. The starch that is not absorbed by the body is called resistant starch, and it is considered dietary fiber. It is also a source of nutrition for intestinal flora, which make important vitamins (and intestinal gas). 

Both the (+)- and (-)- enantiomers of limonene were transformed by larvae of the cutworm Spodop-tera litura (Miyazawa et al. 1998). For both of them the reactions involved are (a) dihydroxylation between C-8 and C-9 and (b) oxidation of the C-1 methyl group to carboxyl. These transformations were not dependent on the intestinal microflora in contrast to the transformation of a-terpinene to p-mentha-l,3-dien-7-ol and p-cymene whose formation could be attributed to the intestinal flora. 

Penicillins (amoxicillin, ampicillin) Broad-spectrum antibiotics may alter intestinal flora, Decrease efficacy of COCs, although the... 

Drugs absorbed by active transport mechanisms appear to have a delayed rate, but not extent of absorption, in the neonatal period [20]. The absorption of vitamin K depends, to some extent, on the development of intestinal flora. 

Rowland IR, Davies MJ, Grasso P. 1978. Metabolism of methylmercuric chloride by the gastro-intestinal flora of the rat. Xenobiotica 8 37-43. 

Drasar BS, Shiner M, Mcloed GM Studies on the intestinal flora. The bacterial flora of the gastrointestinal tract in healthy and achlorhydric persons. Gastroenterology 1969 56 71— 79. 

Simon GL, Gorbach SL Intestinal flora in health and disease. Gastroenterology 1984 86 174-193. 

Reback JF Studies of Intestinal Flora of White Rat thesis University ofNotre Dame, Indiana, USA, 1942. 

Greenlee HB, Gelbart SM, DeOrio AJ, Fran-cescatti DS, Paez J, Reinhardt GF The influence of gastric surgery on the intestinal flora. Am J ClinNutr 1977 30 1826-1833. 

Repeated oral administration of an antibiotic that reaches very high concentrations within the GI lumen could have profound effects on intestinal flora [ 12,13]. As expected, rifaximin markedly reduced fecal bacterial counts during oral intake but the effect was short-lasting since the bacterial population recovered within 1-2 weeks from the end of treatment (table 4) [82], Most importantly, fungal colonization occurred very rarely. Indeed, Candida albicans, which has been implicated in the pathogenesis of antibiotic-associated diarrhea [82, 83], was isolated from the fecal samples of only 2 out of 10 patients given 1,200 mg of rifaximin daily [81] and in none of the volunteers taking 800 mg daily [82],... 

Minimal effects on intestinal flora were seen with rifaximin administration [9, 35]. In an early study, performed on healthy volunteers who received a short-term (5 days) rifaximin treatment, the observed changes in bowel flora returned to baseline levels within 1-2 weeks [9]. In a recent investigation fecal samples of patients with ulcerative colitis given three 10 day courses of the antibiotic were cultured and the different microbial species quantitated. Despite the high dose (i.e. 1800 mg daily) of rifaximin used there was only a minor change in bacterial counts which reverted back to pre-treatment values during the washout period [35]. It appears therefore that administration of this antibiotic does not disrupt intestinal microbial ecology. 

In a recent study, we found no acquisition of rifaximin resistance in 27 rifaximin-treated subjects colonized by Enterococcus [37]. The MIC50 and MIC90 for the treatment group (rifaximin at a dose of either 400 or 200 mg twice daily for 3 days) were similar (16-64 pg/ml). In two published studies, rifaximin resistance was shown to occur in the bacterial flora of individuals who received treatment with rifaximin at a dose of 800 mg/day for 5 days [9, 27]. Within 1-2 weeks after the end of rifaximin treatment, resistance rates appeared to have decreased to less than 20% of the intestinal flora. The resistant strains detected during treatment appeared to be unstable and unable to persistently colonize the intestinal tract. 

While the emergence of rifaximin-resistant strains has been observed during the course of treatment, these strains disappear from the intestinal flora within 1-2... 

Mette U, Werner H, Krasemann C, Ungerechts J The effect of antimicrobial agents on human intestinal flora, with particular reference to Bacteroides species. Infection 1980 8(suppl 2) S215-S218. 

Duchman R, Kaiser I, Hermann E, Mayet W, Ewe K, Meyer zum Buschenfelde KH Tolerance exists towards resident intestinal flora but is broken in active inflammatory bowel disease (IBD). Clin Exp Immunol 1995 102 448-455. 

Duchmann R, May E, Heike M, Knolle P, Neu-rath M, Meyer zum Buschenfelde KH T cell specificity and cross-reactivity towards enterobacteria, Bacteroides, Bifidobacterium and antigens from resident intestinal flora in humans. Gut 1999 44 812-818. 

Duchmann R, Schmitt E, Knolle P, Meyer zum Buschenfelde KH, Neurath M Tolerance towards resident intestinal flora in mice is abrogated in experimental colitis and restored by treatment with interleukin-10 or antibodies to interleukin-12. Eur J Immunol 1996 26 934-938. 

The rate and selectivity of absorption by the GI tract are highly dependent on many conditions. The type of chemical, its molecular weight, molecule size and shape, acidity, susceptibility to attack by intestinal flora, rate of movement through the GI tract, and many other factors affect the rate of absorption. 

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