Gastrointestinal tract microflora colonization

The gut microflora consist of microorganisms, mainly bacteria, of the gastrointestinal tract. The small intestine of the adult human is about 4.0 m long. The large intestine, or colon, is about one-third this length (1.5 m). The colon receives 1.5-2.0 liters of water per day, most of which is absorbed. Only 150-200 ml of water is lost in the feces. The colon also absorbs sodium and chloride originating from the diet and from secretions of the small intestine. The lumenal surface of the large intestine secretes mucus, as does the small intestine. However, the mucosa of the colon contains crypts but lacks viUi. 

Extensive data are available on the prebiotic efficacy of oligosaccharides from in vitro models representing the human colon and from human clinical trials. Whether results from these studies can be extended to animals needs to be determined. The physiology and microflora of the gastrointestinal tract will vary from animal to animal and in most cases there may be limited or no knowledge of the microecology. 

The large intestine is a part of the gastrointestinal tract with diverse microflora which synthesizes significant amounts of vitamin B2, mainly as free riboflavin. The variability of microflora in the human gut is dependent on dietary habits. It has been proven that vegetable-based diet increases the synthesis of riboflavin in the colon (linuma 1955). In vivo colonic absorption was demonstrated in rats... 

The absorption of quercetin glycosides is complex. Flavonol-rich foods contain a mixture of many different types of conjugate, aU of which may be absorbed in a different manner. Quercetin rhamnoglucosides such as rutin, commonly foimd in plant foods, appear only to be absorbed in the large intestine after hydrolysis by the colon microflora. Late absorption in the gastrointestinal tract leads to... 

The ability of the probiotic strain to persist in the gut has been identified as one important prerequisite of probiotic efficacy. Indeed, a number of probiotic products claim that their strains colonize the human gastrointestinal tract. However, it is more likely that after cessation of probiotic feeding, the vast majority of probiotic strains fall below detection. This is not imexpected since the human gut microflora provides a robust barrier to the establishment of exogenous micro-organisms. 

Intestinal microflora are an essential component of human physiology because they act as a barrier against colonization of the gastrointestinal tract by pathogenic bacteria. They also play an important role in the digestion of food and in the metabolism of xenobiotics. 

It was reported [93] that flurbiprofen-cyclodextrin prodrugs were stable in the pH environment of the gastrointestinal tract and hydrolyzed to release free flurbiprofen by the action of enzymes produced by microflora in rat colon. Furthermore, the prodrug showed a great potential in treatment of colitis induced by acetic acid since it significantly decreased the extent and severity of colonic damage induced by acetic acid. 

The competitive exclusion concept was originated by Nurmi and Rantala (1973), based on the study of Salmonella in chickens. Newly hatched birds in modern hatcheries are not able to obtain the normal gut flora of adult birds. As a result, the intestines of chicks can be easily colonized by foodbome pathogens when present. When the chickens were inoculated immediately after birth with the intestinal content of a Salmonella-free adult bird, the frequency of Salmonella infections was radically reduced and the number of Salmonella needed to colonize the ceca of chicks increased. Hence, the normal gastrointestinal microflora of adult chickens can competitively exclude Salmonella from colonizing the naive intestinal tract of chicks. 

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