Intestinal colonization with phylogenetic group B2 Escherichia coli related to inflammatory bowel disease: a systematic review and meta-analysis

Background and objectives. Increased numbers of Escherichia coli and, furthermore, specific subtypes of E. coli, such as E. coli of the phylogenetic groups B2 and D have been found in the intestine of patients with inflammatory bowel disease (IBD). In this review, we wanted to evaluate the relationship between B2 and D E. coli intestinal colonization and IBD. Methods. A systematic review with meta-analyses. We included studies comparing colonization with B2 and D E. coli in IBD patients and in controls. Random-effects and fixed-effect meta-analyses were performed. Results. We included 7 studies on 163 patients with IBD and 89 controls. Among IBD patients, 57 patients had ulcerative colitis (UC) and 95 Crohn's disease (CD). Random-effects meta-analysis showed that IBD patients were more likely to have B2 E. coli intestinal colonization compared with controls (odds ratio [OR]: 2.28; 95% confidence interval [CI]: 1.25-4.16). There was little between-study heterogeneity (I-2=0). The result was confirmed in subgroup analyses of patients with UC (OR: 3.58; 95% CI: 1.62-7.90), but not CD (OR: 1.94; 95% CI: 0.98-3.82). Intestinal colonization with phylogenetic group D E. coli was not found to be related to IBD, UC or CD. Conclusions. Our study reveals that intestinal colonization with phylogenetic group B2 E. coli is associated with UC. Due to the design, we are unable to determine if the colonization with B2 E. coli leads to the development of the disease or the disease increases the risk of colonization with B2 E. coli.