Ox gall

Abstract: Few studies have been conducted on antimicrobial resistance in lactobacilli, presumably because of their nonpathogenic nature as anaerobic commensals. We assessed resistance in 43 type strains and isolates representing 14 species by using agar disk diffusion and MIC analysis in MRS medium. Most noteworthy were two general phenotypes displayed by nearly every strain tested: (i) they were more susceptible (up to 256-fold in some cases) to the deconjugated bile acid cholic acid than to the conjugate taurocholic or taurodeoxycholic acid, and (ii) they became susceptible to aminoglycosides when assayed on agar medium containing 0.5% fractionated bovine bile (ox gall). Two-dimensional MIC analyses of one representative strain, Lactobacillus plantarum WCFS1, at increasing concentrations of ox gall (0 to 30.3 mg/ml) displayed corresponding decreases in resistance to all of the aminoglycosides tested and ethidium bromide. This effect was clinically relevant, with the gentamicin MIC decreasing from >1,000 to 4 mug/ml in just 3.8 mg of ox gall per ml. In uptake studies at pH 6.5, [G-3H]gentamicin accumulation increased over control levels when cells of this strain were exposed to bile acids or reserpine but not when they were exposed to carbonyl cyanide m-chlorophenylhydrazone. The effect was dramatic, particularly with cholic acid, increasing up to 18-fold, whereas only modest increases, 3- and 5-fold, could be achieved with taurocholic acid and ox gall, respectively. Since L. plantarum, particularly strain WCFS1, is known to encode bile salt hydrolase (deconjugation) activity, our data indicate that mainly cholic acid, but not taurocholic acid, effectively permeabilizes the membrane to aminoglycosides. However, at pHs approaching neutral conditions in the intestinal lumen, aminoglycoside resistance due to membrane impermeability may be complemented by a potential efflux mechanism.

Abstract: The promoter activity of the upstream region of the bile-inducible gene betA from Bifidobacterium longum subsp. longum NCC2705 was characterized. DNA fragments were cloned into the reporter vector pMDYAbfB, and the arabinofuranosidase activity was determined under different in vitro conditions. A segment of 469 bp was found to be the smallest operational unit that retains bile inducibility. The reporter activity was strongly affected by the presence of ox gall, cholate, and conjugated cholate, but not by other bile salts and cell-surface-acting compounds. Remarkably, this bile-inducible system was also active in other bifidobacteria containing betA homologs.

Abstract: In vitro gut fermentation systems are relevant tools to study health benefits of foodstuffs Most of them are commonly used to investigate the degradation of nutrients or the development of gut flora Using these models, strong cytotoxic effects of the resulting samples on cultured cells were observed Hence, the aim of the present study was to develop a modified in vitro fermentation model that simulates the whole digestive tract and generates fermented samples that are suitable for testing in cell culture experiments Wholemeal wheat flour (wwf) was digested and fermented in vitro with a fermentation model using different ox gall concentrations (41·6 and 0·6 g/l) The resulting fermentation supernatants (fs) were characterised for metabolites and biological effects in HT29 cells The fermentation of wwf increased chemopreventive SCFA and decreased carcinogenic deoxycholic acid (DCA) The strong cytotoxic effects of the fs, which were partly due to cholic acid and DCA, were diminished by lowering the ox gall concentration, allowing the use of the samples in cell culture experiments In conclusion, an in vitro digestion model, which can be used to study the effects of foodstuffs on chemoprevention and gut health in colon cells, is introduced and its physiological relevance is demonstrated

Abstract: Five strains of a novel thermotolerant lactic acid bacterium, Lactobacillus thermotolerans, isolated from chicken feces were assayed for acid and bile tolerance. Cultures of L. thermotolerans were grown anaerobically at 42°C in four different conditions, Man-Rogosa-Sharpe (MRS) broth at pH 6.5, MRS broth at pH 3.0, MRS broth supplemented with 0.3% (w/v) ox gall and MRS broth supplemented with 7 mM sodium taurocholate, respectively. All strains showed an acid tolerance when incubated at pH 3.0 over a period of 4 h. L. thermotolerans demonstrated significant changes of absorbance ( p<0.05) from the control when cultured with 0.3% bile concentration. Strain JCM11427 seemed to show the highest tolerance to bile. However, statistical analyses revealed no significant differences. The conjugated bile salt (sodium taurocholate) at physiological concentration (7 mM) had no effect on growth of the bacterial strains.