Prevalence of Species in the Ileum of Crohn's Disease Patients and Controls.

are common contaminants of food products, but their prevalence in the human gut is poorly documented. have been implicated in Crohn's Disease (CD, an inflammatory bowel disease) however their role in CD is controversial. We performed highly sensitive PCR assays of specific sequences for the gene of and the gene of . We analyzed a total of 470 ileal samples taken from 338 participants (262 CD patients and 76 controls) belonging to three independent cohorts. All patients and controls were phenotyped and genotyped for the main CD susceptibility variants: , and . were found in 7.7% of ileal samples (respectively 7.9 and 7.6% in controls and CD patients) corresponding to 10% of participants (respectively 11.8 and 9.5% in controls and CD patients). and were the most frequently identified species. The bacteria were more frequent in resected specimens, lymph nodes and Peyer's patches. were no more likely to be detected in CD tissues than tissues from inflammatory and non-inflammatory controls. CD patients treated with immunosuppressants were less likely to be carriers. In conclusion, this work shows that species are frequently found at low levels in the human ileum in health and disease. The role of species in this ecosystem should now be explored.