Abstract Background and aims Adherent Invasive E. coli (AIEC) are found in over one-third of patients with ileal Crohn’s disease, where they are thought to contribute to inflammation and intestinal barrier disruption. However, the bacterial gene factors enabling AIEC persistence under inflammatory conditions remain largely unknown. To address this, we performed a genome-wide transposon sequencing (TnSeq) screening to identify AIEC fitness determinants during colitis. Saturated mutant libraries of the AIEC strain LF82 and the laboratory E. coli K12 MG1655 were administered into mice at baseline and in the context of dextran sodium sulphate (DSS)-induced colitis. This allowed systematic identification of essential genes across the cecum, colon, ileum and jejunum under healthy and inflammatory conditions. Methods Among colitis specific genes, oxc, encoding oxalyl-CoA decarboxylase, was uniquely essential for LF82 colonization, but not for MG1655. We showed that the isogenic Δoxc mutant exhibited impaired motility, reduced flagellar expression and biofilm formation, lower resistance to acidic and oxidative stress and significantly reduced survival in macrophages. It also induced lower TNF-α secretion, indicating attenuated pro-inflammatory potential. In vivo, the Δoxc mutant failed to persist during DSS-induced colitis compared to the WT and complemented strains. The mutant was outcompeted by the WT strain and it induced an attenuated colitis phenotype. Anticipated impact Metabolomic analysis showed a disturbed ADP/ATP ratio in Δoxc mutant, suggesting an altered energy metabolism. Importantly, this role of oxc appears specific to AIEC, with no phenotypes observed in MG1655 and commensal E. coli strains. Transcriptomic analysis of Δoxc revealed a downregulation of the prp operon, involved in propionate metabolism but the precise interplay between oxalate and propionate remains unclear. We will investigate this mechanistic link using RNA-seq, metabolomics, and in vivo functional assays to define the metabolic network of LF82. ECCO Funding will support these multiomics and translational studies to validate new AIEC-specific targets for therapeutic intervention in IBD.
Toumi et al. (Thu,) studied this question.