Consistently, Trp-treated conventional mice had reduced inflammatory markers including MPO activity (Fig. 5D) and TNF-α (Fig. 5E) and IL-1β (Fig. 5F) levels compared with the E. coli group, but no significant differences were detected in these inflammatory markers between Trp-treated gut-dysbiotic mice and gut-dysbiotic mice upon E. coli infection (Fig. 5D–F). Here, MPO is linked to escherichia coli infection.