The CpxRA two-component system of adherent and invasive Escherichia coli contributes to epithelial cell invasion and early-stage intestinal fitness in a dysbiotic mouse model mediated by type 1 fimbriae expression

Crohn’s disease (CD) is an inflammatory bowel disease that is represented as a chronic inflammatory disorder of the gastrointestinal tract (1, 2). Although the detailed etiology of CD is still unclear, several factors appear to be involved in the onset and progression of CD, including genetic, immunological, and infectious factors (3–5). Notably, gut dysbiosis accompanied by gastrointestinal inflammation is the most common manifestation (6, 7). Given that gut dysbiosis is defined by decreased bacterial diversity and an imbalanced microbiota composition, it is speculated that certain bacteria, known as pathobionts, typically existing in symbiosis but capable of triggering disease under specific conditions, are involved in CD. To date, some bacterial species have been identified as suspicious (6–14). Among such bacteria, a pathobiont, adherent and invasive Escherichia coli (AIEC), is significantly prevalent in CD patients and has been widely accepted to be linked to CD (12, 15–18). AIEC strongly adheres to and invades intestinal epithelial cells, penetrates the epithelial barrier, survives within macrophages, moves to deep tissues, and induces inflammatory responses, along with secreting proinflammatory cytokines (19).