Abstract
Escherichia coli is a regular inhabitant of the gut microbiota throughout life. However, its role in gut health is controversial. Here, we investigated the relationship between the commensal E. coli strain CEC15 (CEC), which we previously isolated, and the intestine in homeostatic and disease-prone settings. The impact of CEC was compared to that of the probiotic E. coli Nissle 1917 (Nissle) strain. The expression of ileal and colonic genes that play a key role in intestinal homeostasis was higher in CEC- and Nissle-mono-associated wild-type mice than in germfree mice. This included genes involved in the turnover of reactive oxygen species, antimicrobial peptide synthesis, and immune responses. The impact of CEC and Nissle on such gene expression was stronger in a disease-prone setting, i.e. in gnotobiotic IL10-deficient mice. In a chronic colitis model, CEC more strongly decreased signs of colitis severity (myeloperoxidase activity and CD3+ immune-cell infiltration) than Nissle. Thus, our study shows that CEC and Nissle contribute to increased expression of genes involved in the maintenance of gut homeostasis in homeostatic and inflammatory settings. We show that these E. coli strains, in particular CEC, can have a beneficial effect in a chronic colitis mouse model.
Highlights
Escherichia coli, a member of the Proteobacteria, is a Gram-negative facultative anaerobe with one of the most diverse lifestyles of all microbes and includes commensal, probiotic, and highly pathogenic strains[1]
We investigated the effect of CEC and Nissle in mono-associated IL10−/− mice, three weeks post-colonization, a time interval previously used to observe the effect of colitogenic indigenous E. coli strains in 129S6/SvEv IL10−/− mice[18]
Considering phenotypic diversity at the strain level would aid the assessment of how resident E. coli may affect gut health and disease outcomes, as demonstrated by a recent study[30]
Summary
Escherichia coli, a member of the Proteobacteria, is a Gram-negative facultative anaerobe with one of the most diverse lifestyles of all microbes and includes commensal, probiotic, and highly pathogenic strains[1]. The disruption of the microbiota composition (or dysbiosis) that accompanies several human diseases is characterized by the expansion of Enterobacteriaceae, including E. coli This has been shown for Crohn’s disease (CD)[11], with a high prevalence of www.nature.com/scientificreports/. Mono-association of mice genetically prone to inflammation with E. coli strains, originally isolated from mice gut microbiota, results in intestinal inflammation[17,18,19]. The role of indigenous E. coli toward gut health is far from clear and requires further investigation Another commensal E. coli isolate failed to induce disease in antibiotic-pretreated IBD-susceptible mice, despite robust colonization[20]. Clinical trials have shown a beneficial effect of Nissle for the maintenance of remission in UC, similar to that of mesalazine[23]
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