Changes in bacterial composition and enzymatic activity in ileostomy and ileal reservoir during intermittent occlusion: a study using dogs

High temporal and inter-individual variation detected in the human ileal microbiota

The diversity and temporal stability of the predominant bacteria in the human ileum was studied with the use of ileal effluent samples of seven individuals with Brooke ileostomies. The total number of bacteria within the ileal effluent was in the range of 10⁷ -10⁸ bacteria per gram (wet weight). The diversity of the bacteria in the ileal effluent showed marked differences compared with that in faecal samples from age-matched healthy adults. The ileal effluent had a higher relative abundance of species within the orders Lactobacillales and Clostridiales, mainly Streptococcus bovis-related species, and the Veillonella group, and a lower proportion of species related to Ruminococcus gnavus, R. obeum and Bacteroides plebeius. In addition, inter-individual differences were found, indicative of a highly personal ileal microbiota profile. Furthermore, temporal profiles showed large fluctuations per individual over a period of 9-28 days (average similarity over a period of 9 days was as low as 44%), and differences between morning and afternoon profiles were observed. Parallel cloning and sequencing efforts revealed several phylotypes that were not identified in previous studies (12 out of 65 phylotypes showed less than 97% sequence similarity with previously reported sequences). Achaea were found to be below detection limit by quantitative PCR. Overall, the results indicate that the microbiota of the human ileum is relatively unstable, less complex and consisting of different dominating phylotypes when compared with the colonic microbiota.

Impairment of epithelial transport but not of barrier function in idiopathic pouchitis after ulcerative colitis

BACKGROUND AND AIMS

Little is known of the permeability of ileoanal pouches. Hence the aim of the present study was to determine changes in permeability and mucosal function after ileo-pouchanal anastomosis (IPAA) in patients with ulcerative colitis.

MATERIALS AND METHODS

Biopsies were taken from 43 patients (male:female ratio 28:15; mean age 35.2 (12.5) years) prior to colectomy (ileum prior to pouch), prior to closure of ileostomy (deviation), and after closure of ileostomy (intact pouch) in the case of pouchitis, and from 14 healthy controls. Tissues were mounted in a miniaturised Ussing chamber. Epithelial and subepithelial resistance was determined by transmural impedance analysis. Active Na(+)-glucose cotransport was measured as change in short circuit current after stepwise addition of glucose, and active Cl(-) secretion was measured after stimulation with theophylline and prostaglandin E(2).

RESULTS

Neither epithelial resistance nor mannitol fluxes were significantly altered compared with intact controls, indicating no barrier defect in pouchitis. Subepithelial resistances of intact pouches and pouchitis were increased compared with deviation (18.2 (1.6) and 24.3 (1.5) v. 13.6 (1.0) Omegaxcm(2)) consistent with an adaptive thickening of the subepithelial layer. In contrast, active Cl(-) secretion of pouchitis tissues was reduced versus intact pouch and controls (1.4 (0.3) v. 4.3 (0.7) and 4.6 (0.7) micromol/h/cm(2)), and Na(+)-glucose cotransport of pouchitis was reduced compared with intact pouch and controls (1.8 (0.5) v. 4.2 (0.8) and 8.8 (1.3) micromol/h/cm(2)).

CONCLUSIONS

Ileal mucosa in pouchitis and terminal ileum prior to IPAA exhibit impaired secretory and absorptive transport functions whereas the epithelial barrier function remains unchanged. This differs from findings in ulcerative colitis. Thus the hypothesis that pouchitis represents a remanifestation of ulcerative colitis has to be questioned.

Starch and fiber fractions in selected food and feed ingredients affect their small intestinal digestibility and fermentability and their large bowel fermentability in vitro in a canine model

The digestion of legumes, cereal grains, cereal and potato flours and grain-based foods in dogs was studied using two in vitro model systems. The first simulated the stomach and small intestine through the additions of acid and enzymes and large bowel fermentation through use of fecal inocula from dogs, and the second simulated small intestinal fermentation using canine ileal chyme as the bacterial source. All substrates were analyzed for total dietary fiber (TDF) including insoluble and soluble components, and starch fractions: rapidly digestible starch, slowly digestible starch, resistant starch (RS) and total starch. Legumes had high TDF and RS concentrations (mean 36.5 and 24.7%, respectively), resulting in lower ileal digestible starch and total digestible starch concentrations (mean 21 and 31%, respectively). Seventy-four percent of the TS in the cereal grains group was rapidly digestible starch plus slowly digestible starch compared with the flour group, where the corresponding value was 95%. This related to the processing of cereals to flours, in which TDF and RS concentrations were reduced markedly. This increased ileal digestible starch concentrations in the flour group (65%) versus the cereal grains group (60%). Ileal digestion of starch in grain-based food products like macaroni and spaghetti was high (96 and 92%, expressed as a percentage of TS, respectively). Fermentation of substrates with ileal microflora was influenced by substrate chemical composition, with the flour group exhibiting the highest organic matter disappearance values. The legume group had a high total short-chain fatty acid concentration (7.8 mmol/g organic matter fermented), perhaps as a result of fermentation of TDF as well as starch components. A database such as this one provides information about utilization of foods and feeds in the dog and potentially in humans.

Inability of Lactobacillus casei strain GG, L. acidophilus, and Bifidobacterium bifidum to degrade intestinal mucus glycoproteins

BACKGROUND

Lactic acid bacteria have been suggested for use in the prevention of relapse of ulcerative colitis and of recurrent pouchitis. These strains may not damage the protective intestinal mucus glycoproteins.

METHODS

Lactobacillus casei strain GG and strains isolated from a commercial fermented product (Lactobacillus acidophilus, Bifidobacterium bifidum, and a mesophylic lactic culture) were cultured in vitro on hog gastric mucin and human intestinal glycoproteins. Furthermore, germ-free rats were mono-associated with Lactobacillus GG and poly-associated with the other strains. Glycoproteins were isolated from rat distal ileum, cecum, and colon. Mucus degradation was established by assaying carbohydrates (hexosamines, hexoses, pentoses), proteins, and blood group antigenicity.

RESULTS

All strains colonized the intestinal mucus but were not found in the deep crypts. Degradation of mucus glycoproteins was observed neither in vitro nor in vivo.

CONCLUSION

The tested strains do not break down intestinal mucus glycoproteins and thus far are safe to use for therapy.

Pouchitis: result of microbial imbalance?

To elucidate the role of microbiological factors in pouchitis, this study investigated the composition of ileal reservoir microflora, the mucus degrading capacity of bacterial enzymes as well as the pH and the proteolytic activity of pouch effluent. Stool samples were collected from five patients with pouchitis and nine patients without pouchitis. The flora of patients with pouchitis had an increased number of aerobes, a decreased ratio anaerobes to aerobes, less bifidobacteria and anaerobic lactobacilli, more Clostridium perfringens, and several species that were not found in control patients (for example, fungi). Furthermore the pH was significantly higher in patients with pouchitis (median value 6.5) than in control patients (5.4). To find out if the pH might influence the breakdown of intestinal mucus glycoproteins, the activity of glycosidases and proteases, and the degradation of hog gastric mucin by the pouch flora was tested at pH 5.2-7.6. Some glycosidases were inhibited, others were stimulated by a low pH, however, in each sample the proteolytic activity was inhibited for 75% at pH 5.2 compared with pH 6.8 and 7.6. Degradation of hog gastric mucin by the pouch flora was an active process at pH 7.2: within two to four hours of incubation more than half of the mucin was degraded. At pH 5.2 it took twice as long. It is concluded that pouchitis possibly results from instability of the flora in the pouch, which causes homeostasis to disappear (dysbiosis), and the protection of the pouch epithelium by the mucus layer becomes affected by increased activity of bacterial and host derived enzymes.

Anaerobes and their fermentation products in faeces of patients with familial adenomatous polyposis before and after subtotal colectomy and ileorectal anastomosis

In view of the importance of short-chain fatty acids (SCFA) for the colonic epithelial function and their possible relation with the reported spontaneous regression of rectal polyps after subtotal colectomy with ileorectal anastomosis, we compared the SCFA concentrations in faeces of five familial adenomatous polyposis (FAP) patients before, and in 10 FAP patients after operation to each other and to those of 10 healthy controls. Anaerobe cultural counts and concentrations of organic acids were also investigated in the same faecal samples from FAP patients and controls. The preoperative cultural counts were not significantly different from those of the controls. After colectomy, the Bacteroides (P < 0.002; P < 0.02), and bifidobacteria counts (P < 0.02; P < 0.005) were decreased compared to controls and untreated FAP patients. The ratio of acetic acid to total SCFA significantly increased, which coincided with a proportional decrease of the other SCFA. The frequently observed regression of rectal polyps after colectomy cannot be explained from these results. One would rather expect a possible stimulation of polyp growth and dedifferentiation of colonic epithelial cells.