With the aim of providing an anti-bacterial composition against oral bacteria, and the like, that induce proliferation or activation of Th1 cells in the intestinal tract, it was discovered that bacteria that restrict colonisation of the intestinal tract, and the like, by said oral bacteria, and the like, are among the intestinal flora. Moreover, the intestinal bacteria that restrict intestinal colonisation, and the like, by the oral bacteria, and the like, were successfully isolated.