HP and gastritis: To evaluate the effect of thiopeptide-positive C. acnes on H. pylori-induced gastritis in vivo, GF INS-GAS mice were inoculated with thiopeptide-positive C. acnes MIT 18-1879-A3, H. pylori SS1, H. pylori 1 week before C. acnes (Hp + Ca), C. acnes 2 weeks before H. pylori (Ca + Hp), or no bacteria.