Gut flora

The level of antibiotic resistance of the gut flora of pigs has been found to be influenced by factors other than the inclusion of antibiotics in the diet " " such factors include the herd environment, history and the opportunity for cross-contamination. 

It can be argued that the gut flora provides an additional trophic level in ruminants (Steinhour et al. 1982). This should result in a larger A N in ruminants than in non-ruminant herbivores. As many domesticated animals are ruminants this is a factor that has to be taken into account. Available 5 N data does not seem to show systematic differences between the categories ruminants and non-ruminants, although systematic species differences exist. 

RL Smith. The role of the gut flora in the conversion of inactive compounds to active metabolites. In A Symposium on Mechanisms of Toxicity. WN Aldridge, ed. New York Macmillan, 1971, pp. 228-244. 

L. Linday, J. Dobkin, and T. Wang, Digoxin inactivation by the gut flora in infancy and childhood, Pediatrics, 544 (1987). 

Several bacteria in the natural gut flora or non-pathogenic bacteria which can colonise the gut have been shown to have preventive or even therapeutic effects on pathogens. Most commonly used and studied are bifidobacteria and lactobacilli (see Fig. 13.2) they have been shown to stimulate the innate immune system to produce cytokines, antimicrobial compounds and other metabolites affecting either the host and/or enteric bacteria (Aattouri et al., 2001 Xuan et al., 2001 Kralik et al, 2004 Scharek et al., 2005 Tannock, 2005 Davis et al., 2006). 

Riordan SM, Mclver CJ, Wakefield D, Duncombe VM, Thomas MC, Bolin TD Small intestinal mucosal immunity and morphometry in luminal overgrowth of indigenous gut flora. Am J Gastroenterol 2001 96 494-500. 

Liu Q, Duan ZP, Ha DK, Bengmark S, Kurto-vic J, Riordan SM Symbiotic modulation of gut flora Effect on minimal hepatic encephalopathy in patients with cirrhosis. Hepatololy 2004 39 1441-1449. 

In subacute toxicity studies only the highest rifaximin dose (i.e. 100 mg/kg, corresponding to 25 times the therapeutic dose in humans) induced mild toxic effects (like, for instance, acute gastroenteritis) connected to the topical GI action of the drug [59, 255], A dose-dependent increase of the total cholesterol value was recorded in female animals [255], most likely due to an alteration of biliary acid metabolism consequent to the antibiotic effect on gut flora [256]. 

Hart AL, Stagg AJ, Frame M, Graffner H, Glise H, Falk P, Kamm MA Review article The role of the gut flora in health and disease, and its modification as therapy. Aliment Pharmacol Ther 2002 16 1383-1393. 

Guarner F, Malagelada JR Gut flora in health and disease. Lancet 2003 361 512-519. 

Two concerns with all antimicrobial agents intended for oral administration are the risk of depleting normal gut flora and the potential to induce antibacterial resistance. These aspects have been studied in several trials. 

Solga SF, Diehl AM Gut flora-based therapy in liver disease The liver cares about the gut. Hepatology 2004 39 1197-1200. 

Recent experimental data, coming particularly from animal models of IBD, are consistent with the hypothesis that gut flora and bacterial products are implicated in the initiation and/or perpetuation of chronic intestinal inflammation. Purified bacterial products can initiate and perpetuate experimental colitis [1,2]. 

Metabolic reactions in the liver and the small intestine are well documented [24]. However, only sparse information is available on drug metabolism in the eolon. Drug metabolism in the colon can be brought about by the host enzymes in the epithelial cells or by the microbial enzymes in the gut flora. Metabolie aetivities in the wall of the colon can be attributed to the eytochrome P450, esterases, amidases, and various transferases [25]. Reductive drug metabolism does not appear to be important at this site. 

The colonic mucosa resembles the small intestinal mucosa with respect to the spectrum of metabolizing enzymes [26], However, the total metabolic capacity of the colonic wall is inferior, since the mucosal mass in the lower part of the intestine is several times smaller than in the upper part. But this may be more than offset by the high metabolic capacity foimd in the gut flora in the large intestine. 

T. M. Gloster, J. P. Turkenburg, J. R. Potts, B. Henrissat, and G. J. Davies, Divergence of catalytic mechanism within a glycosidase family provides insight into evolution of carbohydrate metabolism by human gut flora, Chem. Biol., 15 (2008) 1058-1067. 

Biotin (vitamin B ) is widespread in foods and is also synthesized by intestinal bacteria. It is a coenzyme for the carboxylation of pyruvate, acetyl-coenzyme-A (CoA), propionyl CoA, and /1-methyl-crotonyl CoA and is involved in fatty acid formation and in energy release from carbohydrates. In humans deficiencies only occur in patients with an abnormal gut flora and manifests itself as exfoliative dermatitis and alopecia. 

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