Intestinal Bacteria Composition and Translocation of Bacteria in Inflammatory Bowel Disease

BACKGROUND Live commensal intestinal bacteria are present in the peripheral blood where they can induce inflammation. OBJECTIVE To evaluate the intestinal bacteria composition and translocation of bacteria in IBD. METHODS Both blood and tissue biopsy samples were collected from adult patients with active/inactive Crohn's disease (CD), active/inactive ulcerative colitis (UC) and healthy individuals. Most of the patients were newly diagnosed and none of them received antibiotics. Using a reverse transcription-quantitative real-time PCR (RT-qPCR) method, we determined the composition of microbiota. NOD2/CARD15 genotyping was also studied. RESULTS Total bacterial DNA concentration was increased in tissue and blood samples of IBD patients compared to healthy controls. Furthermore, the active IBD cases had higher total bacterial DNA concentration levels compared to the inactive cases. Three species characterized dysbiosis in IBD, namely an increase of Bacteroides spp in active and inactive IBD samples, and a decrease in Clostridium leptum group (IV), and Faecalibacterium prausnitzi in both active and inactive IBD patients. No significant association between bacterial translocation and NOD2/CARD15 mutations was found. CONCLUSIONS The composition of the microbiota in IBD patients differs from that of healthy controls. The high rate of bacterial DNA in the blood samples indicates translocation in inflammatory bowel disease.