AiiA Lactonase Suppresses ETEC Pathogenicity Through 3OC12-HSL Quenching in a Murine Model

This study elucidates how the quorum-sensing (QS) signal 3OC12-HSL exacerbates enterotoxigenic E. coli (ETEC) pathogenicity and intestinal barrier dysfunction. In vitro, 3OC12-HSL enhanced ETEC C83902 growth (66.7% CFU increase at 8 h) and dysregulated stress/growth genes (e.g., eight-fold rmf upregulation under static conditions). In synthetic gut microbiota, 3OC12-HSL selectively augmented E. coli colonization (37.6% 16S rDNA increase at 12 h). Murine studies revealed 3OC12-HSL reduced jejunal villus height (381.5 μm vs. 543.2 μm in controls), elevated serum LPS, D-lactate, and DAO, and altered microbial composition (Firmicutes/Bacteroidetes imbalance). The lactonase AiiA reversed these effects by degrading 3OC12-HSL. It abrogated bacterial growth stimulation (in vitro CFU restored to baseline), normalized microbiota diversity (Shannon index recovered to control levels), suppressed pro-inflammatory cytokines (IL-6/TNF-α reduction), and restored intestinal integrity (villus length: 472.5 μm, 20.5% increase vs. ETEC-infected mice). Our findings establish AiiA as a potent quorum-quenching agent that counteracts ETEC virulence via targeted signal inactivation, highlighting its translational value.