AOM/DSS BALB/c mice were inoculated with a WT-ETBF (bft-2), nontoxigenic B. fragilis strain harboring a plasmid containing the active BFT-2 gene (rETBF), or nontoxigenic B. fragilis secreting catalytically inactive BFT (rNTBF). Here, PITX1 is linked to infectious otitis media.