The immune system has a crucial role in the pathophysiology of sepsis, which has been defined as a dysregulated systemic immune response following microbial invasion. However, the mechanisms underlying sepsis survival or susceptibility are not well understood. In this study, Keskey, Alverdy and colleagues show that metabolites from both the infecting pathogen and the gut microbiota of the host are major determinants of survival from bacterial sepsis in mice.

Next, using 16S rRNA sequencing the authors showed that there were no changes in the gut microbiota composition between surviving and non-surviving mice. However, the authors found a significant increase in indole metabolites, which are products of tryptophan metabolism, in surviving mice and FMT-treated mice compared with non-surviving mice.