MUCOSA-ASSOCIATED BACTERIAL-FLORA OF THE HUMAN COLON

Biopsy samples of mucosa were taken during colonoscopy from the proxim al colon and rectum of 12 patients, six with ulcerative colitis (UC) a nd six with non-inflammatory conditions. After anaerobic transport to the laboratory, biopsy specimens were examined by quantitative bacteri ological culture on selective and non-selective media for total aerobi c count, total anaerobic count, Bacteroides spp., lactobacilli, bifido bacteria and asaccharolytic, lactic acid producers. Isolates of the ge nus Bacteroides were identified to species level. Counts from proximal colonic and rectal biopsy samples in the same patient were not signif icantly different. Viable aerobic counts (aerobes and facultative orga nisms) ranged from 2.4 x 10(3) to 1.3 X 10(6) cfu/sample biopsy (5.6 m g) and total anaerobic counts were 10-10(2) times higher at (1.4 X 10( 5))-(3 x 10(7))cfu/sample. Bacteroides spp. predominated at both sites (range 8.6 x 10(4) to 1.4 X 10(7) cfu/sample), comprising 66% of tota l counts from proximal colon (range in individual patients 31-80%) and 68.5% from rectum (range 38-91%). Lactobacilli were isolated from eig ht biopsy samples from five patients, counts ranging from 3.6 x 10(2) to 1 X 10(5) cfu/sample; bifidobacteria were isolated from both sites from 10 of the 12 patients, counts ranging from 50 to 1.8 X 10(6) cfu/ sample. From the 24 biopsy samples, 235 isolates representing 11 speci es of Bacteroides were identified. For any individual patient, only a few species (2-7; mean 4.4) of Bacteroides were found, with just one o r two species predominating. B. vulgatus was cultured from both sample s 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 co mmonest in three, but was not detected in the other six; the majority of other isolates were B. merdae/distasonis, B. ovatus, B. thetaiotaom icron and B. uniformis. B. thetaiotaomicron was isolated from both bio psy samples in all three UC patients with active inflammation (16 of t he 60 isolates from these patients) but from only four of the other 18 samples from non-inflamed colonic mucosa (nine of 175 isolates).