To directly assess the roles of the yfgM and ppiD genes in CDI resistance, we introduced in-frame deletions of yfgM and/or ppiD into secY+ and secYS281F parental strains and performed competition co-cultures with inhibitor cells that deliver CdiA-CTGN05224 or CdiA-CTo10EC869. Here, PPID is linked to clostridium difficile infection.