Mucosa-associated bacterial flora of the human colon

Abstract

Edinburgh EH8 9AGBiopsy samples of mucosa were taken during colonoscopy from the proximal colon and rectum of 12 patients, six with ulcerative colitis (UC) and six with non-inflammatory conditions. After anaerobic transport to the laboratory, biopsy specimens were examined by quantitative bacteriological culture on selective and non-selective media for total aerobic count, total anaerobic count, Bacteroides spp., lactobacilli, bifidobacteria and asaccharolytic, lactic acid producers. Isolates of the genus Bacteroides were identified to species level. Counts from proximal colonic and rectal biopsy samples in the same patient were not significantly different. Viable aerobic counts (aerobes and facultative organisms) ranged from 2.4 X lo3 to 1.3 X lo6 cfu/sample biopsy (5.6 mg) and total anaerobic counts were 10-lo2 times higher at (1.4 X 105)-(3 X lo7) cfu/sample. Bacteroides spp. predominated at both sites (range 8.6 X lo4 to 1.4 X lo7 cfu/sample), comprising 66% of total counts from proximal colon (range in individual patients 31-80%) and 68.5% from rectum (range 38-91 YO). Lactobacilli were isolated from eight biopsy samples from five patients, counts ranging from 3.6 X lo2 to 1 X lo5 cfu/sample; bifidobacteria were isolated from both sites from 10 of the 12 patients, counts ranging from 50 to 1.8 X lo6 cfu/sample. From the 24 biopsy samples, 235 isolates representing 11 species of Bacteroides were identified. For any individual patient, only a few species (2-7; mean 4.4) of Bacteroides were found, with just one or two species predominating. B. vulgatus was cultured from both samples of seven patients (where it was the major isolate in four) and from single samples of two others; B. fragilis was cultured from both sites in six patients, being the major isolate in one patient and second commonest in three, but was not detected in the other six; the majority of other isolates were B. rnerdae/dstasonis, B. ovatus, B. thetaiotaomicron and B. uniformis. B. thetaiotaomicron was isolated from both biopsy samples in all three UC patients with active inflammation (16 of the 60 isolates from these patients) but from only four of the other 18 samples from non-inflamed colonic mucosa (nine of 175 isolates).

Qualitative and quantitative analyses of the bifidobacterial microbiota in the colonic mucosa of patients with colorectal cancer, diverticulitis and inflammatory bowel disease

“…In addition, reduced levels of bifidobacteria in the colorectal mucosa of patients with ulcerative colitis (a manifestation of IBD) have also been reported [26] . In general, our results on the occurrence and levels of total Bifidobacterium are in the range of those reported by Poxton and co-workers [25] in patients with ulcerative colitis. However, our study extends these observations to the level of Bifidobacterium species and differences in the species composition which may more accurately reflect the intestinal microbiota activity.…”

“…Only a few studies with mucosal samples have been conducted in both healthy individuals and patients [24,25] . In this area, the mucosal microbiota of patients suffering inflammatory conditions such as IBS and IBD is the most widely characterized.…”

Microbiomic analysis of the bifidobacterial population in the human distal gut

“…Recently, metagenomic and microbiomic studies based on the analysis of genomic DNA-and rRNA gene libraries have highlighted the diversity of the GIT microbiota and have shown that it consists of many novel and, as yet, unculturable bacterial components (Eckburg et al, 2005;Wang et al, 2005;Gill et al, 2006;Kurokawa et al, 2007;Palmer et al, 2007). However, relatively few bifidobacterial rRNA gene sequences have so far been identified in these metagenomic studies, which are in striking contrast to what was described earlier in several bifidobacterial surveys, which had adopted culture-dependent approaches (Poxton et al, 1997;Harmsen et al, 2000;Fanaro et al, 2003).…”

Bacteria in the Intestine, Helpful Residents or Enemies from Within?

“…Some studies have found greater concentrations of coliforms and aerobic bacteria in patients with severe ulcerative colitis and moderate and severe CD, whereas other studies have reported a decrease in anaerobic and Lactobacillus species in patients with active IBD (31). An investigation of the rectal mucosa-associated bacterial flora in ulcerative colitis patients showed that both the highest bacterial counts and the highest isolation frequency were observed for B. vulgatus, Bacteroides fragilis, and Bacteroides ovatus, in that order (116). Changes in colonization patterns have also been observed (134,142), but the relative contributions of host and bacterial factors to this phenomenon remain to be elucidated.…”