Liver abscess induced by intestinal hypervirulent Klebsiella pneumoniae through down-regulation of tryptophan-IPA-IL22 axis

Hypervirulent <i>Klebsiella pneumoniae</i> (hvKp) is a significant causative agent of invasive hepatic abscess syndrome in Asia, presenting substantial clinical challenges due to its intricate pathogenesis. This study revealed the crucial role of the gut microbiota in fortifying the host's defense against hvKp infection by enhancing interleukin-22 (IL-22), probably through regulating downstream antimicrobial peptides such as Reg3β. In antibiotic-treated mice, we observed that gut microbiota disruption impaired the transformation of tryptophan to indole, a key ligand for the aryl hydrocarbon receptor (AhR), consequently affecting the regulatory functions of IL-22. Our experimental findings revealed that administering rIL-22 or indole propionic acid notably diminished the translocation of hvKp from the intestine to the liver. This research not only underscores the pivotal role of the gut microbiome in modulating tryptophan metabolism and the IL-22 pathway but also highlights its critical function in preventing hvKp migration from the colon to the liver.