Cytokine association with bacterial DNA in serum of patients with inflammatory bowel disease

Background: The pathogenesis of inflammatory bowel disease (IBD) involves the interaction between genetic susceptibility, mucosal immunity, and intestinal bacteria. Bacterial translocation is a common event in these patients and plays an important role in the perpetuation of chronic intestinal inflammation. Blood microbiological cultures, however, are frequently negative. The aim was to evaluate the presence of bacterial DNA (bactDNA) and the associated cytokine response in patients with IBD. Methods: Fifteen healthy donors, 29 patients with ulcerative colitis (UC), and 33 patients with Crohn's disease (CD) were studied. The presence of bactDNA was pursued by PCR followed by nucleotide sequencing analysis. Microbiological cultures were carried out among all controls and patients. Cytokine serum levels were measured by enzyme-linked immunosorbent assay (ELISA). Results: BactDNA was detected in 14 out of 33 patients with CD (42.4%) and in 15 out of 29 patients with UC (51.7%). BactDNA translocation was present in 7 out of 21 (33%) and in 10 out of 15 (34%) patients with CD and UC in remission, respectively. None of healthy controls showed bactDNA in serum. A statistically significant increase in all Th1-derived cytokines in CD but not in UC patients with the presence of bactDNA was observed in comparison with patients without bactDNA and controls. Conclusions: BactDNA is present in IBD patients, irrespective of their disease activity. This fact is associated with a marked Th1-driven immune reaction in CD patients, even in those in remission. Whether bactDNA is inducing or is favored by an increased inflammatory scenario in these patients remains under discussion. (Inflamm Bowel Dis 2008)