Quantitative analysis of bacterial DNA from Mycobacteria spp., Bacteroides vulgatus, and Escherichia coli in tissue samples from patients with inflammatory bowel diseases

Background The etiology of inflammatory bowel diseases is unknown. Mycobacteria spp., Bacteroides vulgatus, and Escherichia coli have been suspected to be involved. The aim of the present study was to examine the possible relationship between inflammatory bowel diseases and these microbes. Methods. We studied 45 patients; 16 with Crohn's disease, 11 with ulcerative colitis, and 18 with colon cancer as controls. We used a real-time quantitative polymerase chain reaction to detect and estimate numbers of bacterial genomes in formalin-fixed, paraffin-embedded tissue samples from the subjects. The bacteria studied were Mycobacterium tuberculosis, M. avium, M. paratuberculosis, B. vulgatus, and E. coli. Immunohistochemical staining was done to locate B. vulgatus and E. coli in tissue samples. Results. The three Mycobacterium species were not detected. B. vulgatus and E. coli were detected more frequently and in greater numbers in samples from patients with inflammatory bowel diseases than in samples from control patients with colon cancer. The frequency and numbers were not related to the severity of the disease. Many bacteria of these species were found within the mucous layer, underneath erosions, in necrotic ulcer bed tissues, and in abscesses. E. coli cells were found in perivascular areas in the proper muscle layer and in germinal centers of lymph follicles. Conclusions. Our results suggest that Mycobacteria spp. are not involved in the etiology of Crohn's disease and that mucosa-associated B. vulgatus and E. coli are not a direct cause of inflammatory bowel diseases, although they may contribute to the diseases by preventing or delaying remission.