Indeed, AOM-treated colonic mucosa was characterized by an oxidative microenvironment, as shown by a significant downregulation of antioxidant genes Nrf2, Prdx2 and Prdx6 and a consistent reduction in the ratio of reduced GSH to oxidized GSH (GSSG), as compared to colonic mucosa of untreated mice (Additional file 5: Figure S1). This evidence concerns the gene PRDX2 and infectious otitis media.