Adherent-invasive Escherichia coli in Crohn's disease: the 25th anniversary

In 1998, Arlette Darfeuille-Michaud, Christel Neut and Jean-Frederic Colombel discovered a novel pathovar of Escherichia coli, adherent and invasive Escherichia coli (AIEC), in the ileum of patients with Crohn's disease (CD), that was genetically distinct from diarrheagenic E. coli, could adhere to and invade intestinal epithelial cells and survive in macrophages. The consistent association between AIEC and CD (approximately 30% across the world), their ability to exploit CD-associated genetic traits, and virulence in preclinical colitis models but not healthy hosts spurred global research to elucidate their pathogenicity. Research focused on integrating AIEC with the microbiome, metabolome, metagenome, host response and the impact of diet and antimicrobials has linked the luminal microenvironment and AIEC metabolism to health and disease. This deeper understanding has led to therapeutic trials and precision medicine targeting AIEC-colonised patients. In November 2023, prominent members of the AIEC research community met to present and discuss the many facets of basic, translational and clinical AIEC fields at 'AIEC: past, present and future' in NYC. This review is a summary of this international meeting highlighting the history of AIEC, knowledge accumulated over the past 25 years about its pathogenic properties and proposes a standardised approach for screening patients for AIEC.