Date Published: April 29, 2019
Publisher: Public Library of Science
Author(s): Jae Gon Lee, Dong Soo Han, Su Vin Jo, A. Reum Lee, Chan Hyuk Park, Chang Soo Eun, Yangsoon Lee, Emiko Mizoguchi.
Adherent-invasive Escherichia coli (AIEC) has been reported as associated with the pathogenesis of inflammatory bowel disease (IBD). We aimed to investigate the characteristics of mucosa-associated E. coli and the clinical significance of AIEC in Korean IBD patients. E. coli strains were isolated from the mucosal tissues of 18 Crohn’s disease (CD) patients, 24 ulcerative colitis (UC) patients, and 9 healthy controls (HC). Adhesion, invasion, and survival assays were performed to evaluate phenotypic features of E. coli isolates and to identify AIEC. The presence of virulence genes and cytokine expression were examined using PCR. In addition, data on IBD-related hospitalization were collected. A total of 59 E. coli strains were isolated (25 from CD, 27 from UC, and 7 from HC). The average levels of adhesion, invasion, and survival were higher in E. coli strains from IBD patients than those from HC (adhesion: 1.65 vs. 0.71, p = 0.046; invasion: 1.68 vs. 0.52, p = 0.039; survival: 519.55 vs. 47.55, p = 0.363). Prevalence of AIEC in HC, CD and UC patients was 22.2%, 38.9% and 37.5%, respectively. E. coli isolates from IBD patients had various virulence genes and were associated with increased expression of TNF-α and IL-17. IBD-related hospitalization within 3 years was 18.8% in patients with AIEC and 11.5% in patients without AIEC. E. coli strains from IBD patients showed high levels of adhesion, invasion, and survival. AIEC strains were identified in both CD and UC patients at a similar rate. AIEC may be associated with sustaining inflammation in the pre-existing inflammatory mucosa.
Inflammatory bowel disease (IBD), including Crohn’s disease (CD) and ulcerative colitis (UC), is characterized by chronic inflammation of the gastrointestinal tract. Although the etiology of IBD is not fully understood, it is generally accepted that genetic susceptibility, environmental factors, and altered intestinal microbiota are involved . A dysbiosis, characterized by an increase in the number of mucosa-associated colitogenic bacteria and a reduction in overall biodiversity, has been suggested as an important contributor to the pathogenesis of IBD . Previous studies have reported that increased numbers of mucosa-associated Escherichia coli strains were observed in patients with IBD [3, 4]. Adherent-invasive E. coli (AIEC), in particular, has been proposed as a possible pathogen that may potentially induce intestinal inflammation .
In the present work, we evaluated characteristics of mucosa-associated E. coli and identified AIEC in Asian IBD patients. E. coli isolates from IBD patients showed higher adhesiveness, invasiveness, and survival capability than those from HC subjects. Prevalence of AIEC strains was relatively higher in IBD patients than HC subjects, and similar in CD and UC patients. AIEC strains from IBD patients were associated with increased expression of proinflammatory cytokines and increased rates of IBD-related hospitalization.