Detection of Listeria monocytogenes by polymerase chain reaction in intestinal mucosal biopsies from patients with inflammatory bowel disease and controls

Background and Aims: Components of the intestinal microflora are believed t o play an important role in the pathogenesis of inflammatory bowel disease (IBD) in genetically susceptible hosts acting either as a non-specific anti genic stimulus or as a specific pathogen. Listeria monocytogenes has been s uggested as an organism with the potential to cause IBD. The objective of t he present study was to investigate the prevalence of L. monocytogenes DNA in intestinal biopsies from patients with IBD and from non-IBD controls by using nested polymerase chain reaction (PCR). Methods: The DNA was extracted from 274 colonoscopic biopsies, which were o btained from 23 patients with Crohn's disease (CD), 28 with ulcerative coli tis (UC) and 39 non-IBD control patients. Nested PCR amplification was used to detect the presence of the L. monocytogenes listeriolysin O (hly) gene. The sequences of positive PCR products were determined and compared with d atabases. Results: The sensitivity of our nested PCR was 10 fg L. monocytogenes DNA. Overall, L. monocytogenes DNA was detected in 13.0% patients with CD, 17.9% patients with UC and 25.6% non-IBD control patients or in 29 of 274 (10.6% ) endoscopic biopsies. Among them, L. monocytogenes DNA was detected in fou r of 67 (6%) biopsies from patients with CD, five of 94 (5.3%) biopsies fro m patients with UC and 20 of 113 biopsies (17.7%) from non-IBD control pati ents. Sequence analysis of positive PCR products demonstrated more than 95% similarity to the hly gene sequence of L, monocytogenes, confirming the au thenticity of our PCR products. Conclusion: Listeria monocytogenes DNA was detected in the intestine of bot h patients with IBD and in non-IBD control patients, probably reflecting th e widespread presence of this organism in the environment. The low yield of positive biopsies in our IBD patients (5-6%) and the fact that the detecti on rate of L. monocytogenes DNA was similar in endoscopic biopsies from IBD patients and non-IBD controls does not support a direct role for L. monocy togenes in the pathogenesis of IBD, at least in New Zealand patients. (C) 2 000 Blackwell Science Asia Pty Ltd.