A gut <i>Eggerthella lenta</i> –derived metabolite impairs neutrophil function to aggravate bacterial lung infection

The composition of the gut microbiota in patients with bronchiectasis has been proven to be distinct from that of healthy individuals, and this disrupted gut microbiota can exacerbate lung infections. However, the responsible microbes and mechanisms in the "gut-lung" axis in bronchiectasis remain unknown. Here, we report that <i>Eggerthella lenta</i> was enriched in the gut, and taurine ursodeoxycholic acid (TUDCA) was enriched in both the guts and sera of patients with bronchiectasis, with both being associated with disease severity. Fecal microbiota transfer from patients with bronchiectasis as well as administration of <i>E. lenta</i> independently exacerbated pulmonary <i>Pseudomonas aeruginosa</i> infections in murine models. <i>E. lenta</i>-associated TUDCA bound adenosine monophosphate-activated protein kinase (AMPK) within neutrophils and interfered with the interaction between liver kinase B1 and AMPK, with a consequential decrease in AMPK phosphorylation. This ultimately reduced ATP production in neutrophils, inhibited their function, and compromised <i>P. aeruginosa</i> elimination from the lung, aggravating tissue injury. Metformin treatment improved disease severity and outcome in the mouse models. In sum, the gut bacterium <i>E. lenta</i> raises the stakes of bacterial lung infection because it causes dysfunction of neutrophils circulated from serum to lung via the metabolite TUDCA. Interventions targeting <i>E. lenta</i> or AMPK phosphorylation may serve as adjunctive strategies to complement existing approaches for managing chronic pulmonary infection in bronchiectasis and other chronic respiratory disease states.