Characterization of mucosa-associatedEscherichia colistrains isolated from Crohn's disease patients in Brazil

Background Crohn's disease (CD) is characterized by chronic inflammation of the human intestine. Several studies have demonstrated that the intestinal mucosa of CD patients in Western countries is abnormally colonized by adherent-invasiveEscherichia coli(AIEC) strains. However, no studies to date have focused on the involvement of suchE. colistrains in CD patients in Brazil. Here, we characterizedE. colistrains associated with the ileal mucosa of Brazilian CD patients (ileal biopsies from 35 subjects, 24 CD patients and 11 controls). Results The colonization level of adherentEnterobacteriaceaeassociated with the ileal mucosa of CD patients was significantly higher than that of the controls. The proportions ofE. colistrains belonging to phylogroups B1 and B2 were two-fold higher in strains isolated from CD patients than in those isolated from controls. CD patients in the active phase harbored 10-fold moreE. colibelonging to group B2 than CD patients in remission. Only a fewE. coliisolates had invasive properties and the ability to survive within macrophages, but 25% of CD patients in Brazil (6/24) harbored at least oneE. colistrain belonging to the AIEC pathobiont. However,fimHsequence analysis showed only a few polymorphisms in the FimH adhesin of strains isolated in this study compared to the FimH adhesin of AIEC collections isolated from European patients. Conclusions Mucosa-associatedE. colistrains colonize the intestinal mucosa of Brazilian CD patients. However, the strains isolated from Brazilian CD patients have probably not yet co-evolved with their hosts and therefore have not fully developed a strong adherent-invasive phenotype. Thus, it will be crucial to follow in the future the emergence and evolution of AIEC pathobionts in the Brazilian population.