I am starting a project to establish an animal model of Helicobacter pylori infection. Based on the literature, I chose female C57 mice, and the bacterial strain is the H. pylori Sydney strain SS1. After four rounds of oral gavage (approximately 10^8 CFU per mouse each time, once every other day), there was still no obvious colonization observed after an 8-week period. When I collected gastric tissue and attempted to culture H. pylori on blood agar supplemented with Dent selective supplement, I found a lot of contaminating bacteria. Could the experts please share your methods for establishing the infection model? How should gastric tissue be collected and processed for H. pylori culture?