Abstract
BackgroundCrohn’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-invasive Escherichia coli (AIEC) strains. However, no studies to date have focused on the involvement of such E. coli strains in CD patients in Brazil. Here, we characterized E. coli strains associated with the ileal mucosa of Brazilian CD patients (ileal biopsies from 35 subjects, 24 CD patients and 11 controls).ResultsThe colonization level of adherent Enterobacteriaceae associated with the ileal mucosa of CD patients was significantly higher than that of the controls. The proportions of E. coli strains 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 more E. coli belonging to group B2 than CD patients in remission. Only a few E. coli isolates had invasive properties and the ability to survive within macrophages, but 25% of CD patients in Brazil (6/24) harbored at least one E. coli strain belonging to the AIEC pathobiont. However, fimH sequence 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.ConclusionsMucosa-associated E. coli strains 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.
Highlights
Crohn’s disease (CD) is characterized by chronic inflammation of the human intestine
Several adherent-invasive Escherichia coli (AIEC) genomes were recently sequenced, and comparative genomic studies of E. coli strains isolated from patients with CD showed that these strains represent a heterogeneous population with a genomic profile similar to that of extraintestinal pathogenic E. coli strains (ExPEC) [17,18,19,20,21]
The proportions of E. coli strains belonging to phylogroups B1 and B2 were two-fold higher in strains isolated from CD patients (B1, 27.9%; B2, 11.5%) than in those isolated from controls (B1, 13.8%; B2, 5.2%)
Summary
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-invasive Escherichia coli (AIEC) strains. The search for specific pathogens in the intestinal mucosa of patients with CD has resulted in the identification in 1998 of several candidates, among which Adherent-Invasive E. coli (AIEC) have much supporting evidence [5]. AIEC bacteria behave like pathobiont bacteria rather than real pathogens, and must share in the evolution of common ancestors with ExPEC strains [9] These bacteria could be the results of an adaptation of non-pathogenic bacteria to environmental factors leading to a phenotypic characteristic. The presence of AIEC in the mucosa of CD patients at initial diagnosis suggests that these microorganisms may play a role in the early stages of disease onset [12]
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