Mucosally associated bacterial flora of the human colon: quantitative and species specific differences between normal and inflamed colonic biopsies

This study quantified and characterised changes to a species level for aerobic and anaerobic bacteria from colonic biopsies of acute ulcerative colitis (UC) comparing them with that of a normal control group. Fresh endoscopic biopsies of the recto–sigmoid region were obtained during flexible sigmoidoscopy from 10 patients suffering an acute attack of UC and a similar number of healthy controls. Quantitative estimation was carried out on selective media for total aerobic, anaerobic, Bacteroides , Bifidobacterium and Lactobacillus spp. (Miles–Misra). Species identification involved gram stain, indole, catalase tests and commercially validated anaerobic, gram-positive and non-enteric fermenting enzyme hydrolysis kits. There was a significant quantitative decrease in growth of Lactobacillus spp. in colitic biopsies (p<0.05). Total aerobic speciation revealed 32 different sub-species with 18 of these found only in UC biopsies. Anaerobic speciation revealed 41 different sub-species with a mean 6.7 species in normal and 4.7 in UC patients. Bacteroides thetaiotaomicron was isolated in significantly increased frequency in UC biopsies (8:10) in comparison with normal (4:10). Our data are consistent with the possibility that a reduction in mucosally associated Lactobacillus bacteria in UC permits proliferation of a large number of potentially pathogenic aerobic species and anaerobic predominance of B. thetaiotaomicron . Keywords: ulcerative colitis, intestinal flora, Lactobacillus , B. thetaiotaomicron .