Objective: To understand why oral inoculation of Helicobacter pylori resulted in continuous colonization of the stomach in germ-free athymic mice, but only temporary colonization in mice that were not germ-free.
Methods: We inoculated germ-free and "not-germ-free" euthymic mice with H. pylori and studied the resulting colonization of the stomach, comparing it against the germ-free athymic mouse model. In addition, we investigated Lactobacillus in the above-described three mouse groups.
Results: H. pylori were detected in all germ-free athymic mice and all germ-free euthymic mice continuously. However, in all euthymic mice that were not germ-free, H. pylori was detected only temporarily after inoculation. Lactobacilli were detected only in the not-germ-free mouse group. The number of H. pylori in the germ-free euthymic mice was significantly lower than in the germ-free athymic mice during the period of this study after inoculation.
Conclusions: We therefore suggest that the growth of H. pylori may be suppressed by the immunological system and eradicated by Lactobacilli previously inhabiting the stomach.