| Irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) including ulcerative colitis (UC) and Crohn’s disease (CD), which etiologies remain elusive, are the frequent intestinal diseases of human. Although there are differences between them on etiologies, mechanisms, clinical symptoms and treatments, they all involve in abnormal enteric flora. Denaturing gradient gel electrophoresis (DGGE) based on 16S rDNA was used in our study to analyze the diversity of species and quantities of dominant bacterium and the similarity of dominant bacterial community in feces between patients and healthy controls. The stability of predominant bacterial community in stool of patients was evaluated by Shannon index and Evenness index. The relative quantities of eleven species of bacterium (they were Bifidobacterium spp., Campylo-bacter spp., C. Coccoides group, Desulfovibrio spp., Enterococcus spp., E. coli spp., F. prausnitzii, Lactobacillus spp., R. productus, Veillonella spp., B. Catenulatum group) was detected through Real-time PCR. We also assayed the concentrations of acetate, propionate, butyrate, isobutyrate, isovalerate in stool samples and analyzed the associativity between the data above and the etiologies or clinical symptoms of the diseases.There was significant difference of predominant flora in feces between IBS patients and healthy controls. The similarity among the individuals of patient cohort (20.3%～ 60.2%), which showed a phenomenon like "convergence", were a little higher than those of healthy cohort (9.5%～65.8%) but less higher than those of the individuals between patient and healthy group. The stabilities of the predominant flora in feces of patients were low for the data of Shannon index and Evenness index (1.89 and 0.65 respectively) being extremely significant smaller than those of healthy group (2.32 and 0.77 respectively). The species of dominant bacteria in stool of patients showed no evident difference from healthy controls but the total quantity of them decreased remarkably (P< 0.01). These data suggested that the serious alteration of flora existed in colon of IBS patients. The amount of Bifidobacterium spp. reduced significantly but a little increased of B. Catenulatum group and Lactobacillus spp. Some species of bacterium, such as F. prausnitzii, R. productus and Veillonella spp., reduced notablely which involved in the metabolisms of short-chain fatty acids (SCFAs) in human colon. Desulfovibrio spp. is a species of bacteria connect to production of H2S in intestine and its quantities in patients were obviously littler than those of health individuals. There was no overgrowth of conditional pathogenic bacterium, such as Campylobacter spp., Enterococcus spp., E. coli spp., C. Coccoides group. We presumed there was no relationship between the occurrence of IBS and the overgrowth of conditional pathogenic bacterium. Probably it was some way in evoking irritable bowel syndrome by flora disequilibrium, plenty diminution of pro-biotics, reductional productions of SCFAs in colon and so on.The similarity of dominant microbiota in stool between UC patients and healthy controls (3.0%～50.1%) were lower than those inside the patient cohort (5.5%～ 69.2%), and more lower than those inside the healthy group (17.7%～80.1%). The structures of the flora in excrement among the patients showed a phenomenon like "branch". There were extremely serious imbalance of intestinal flora of the UC patients because of the lower stabile structure of the predominant flora for its index of Shannon and Evenness (2.54 and 0.92 respectively) were much smaller than those of healthy controls (2.83 and 0.94 respectively), significant decrease of the species numbers of dominant bacterium and sharp landslide of the total quantities of primary species (P-10-6, a=0.01). The numbers of Bifidobacterium spp. decreased obvious-ly but no noticeable changes of Lactobacillus spp. and B. Catenulatum group were found. In spite of the absolute quantities of Campylobacter spp., Enterococcus spp., E. coli spp., C. Coccoides group, there probably were increases in their relative numbers in the flora as the total quantities of dominant species decreased acutely. There was a large effect to the productions of SCFAs from the remarkable reductions of the numbers of F. prausnitzii and R. productus, in addition the number of Veillonella spp. was littler. We presumed that sharp landslide of the whole numbers of the enteric flora, plenty decrease of probiotics such as Bifidobacterium spp., increase of the relative amount of conditional pathogenic bacterium in colon and lesser productions of SCFAs metabolisms maybe induce ulcerative colitis.The similarity of dominant flora in feces of CD patients (0～30.1%) was less than that of healthy group (2.9%～45.6%) and the structures of the flora among the patients showed a phenomenon like "branch", like UC. The structure of predominant flora in stool of CD patients were stabile because there were no significant difference of the diversity and evenness between the two groups (CD,2.59 and 0.93 respectively; healthy controls,2.59 and 0.93 respectively) and the species numbers and the amount of dominant bacterium in fecal flora of patients were also constant. The amounts of Bifidobacterium spp., E. coli spp., R. productus, Veillonella spp., B. Catenulatum group, Enterococcus spp. and Lactobacillus spp. were no significant change in fecal flora of CD patients, but the reduction of Bifidobacterium spp. was relatively obvious (P=0.0533, a=0.05). Campylobacter spp. and Desulfovibrio spp. reduced remark-ably while C. Coccoides group and F. prausnitzii decreased extremely noticeable. We presumed that the inducement of Crohn’s disease may be not the dysbacteria of colon flora, but the significant reduction of F. prausnitzii.The contents of short-chain fatty acids reduced remarkable in stool samples of the IBS, UC, CD patients. As the concentrations of propionate, butyrate, isobutyrate and isovalerate in feces of IBS patients were significantly lower than those of healthy controls, among which the quantity of butyrate changed extremely noticeable, they maybe play a role in low-grade mucosal inflammation which probably is the induction of IBS. The concentrations of the SCFAs we detected in stool samples of UC patients were all decreased quite remarkably, among which the difference of butyrate was the most significant, followed by isobutyrate, the difference of acetate was minimal. The dysbolismus of butyrate in cobn may be the substantial inducement of UC. The contents of acetate, propionate and butyrate in stool samples of CD patients stepped down significantly, among which acetate changed extremely noticeable. The reductions of the three SCFAs might not be the direct cause of the disease, but weaken the inhibition to the abnormal activation of the mucosal immune system that leading to the increased potentiality with the disease. However, our results showed that it was not the relative ratio of SCFAs in colon, but the absolute contents participate in the occurrence of the diseases. |
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