With the aim of proving an antibacterial compositionagainst oral bacteria and the like capable of inducing Thlcell proliferation or activation in an intestinal tract, thepresent inventors have found out that bacteria that suppresscolonization and the like of the oral bacteria and the likein the intestinal tract are present in an intestinalmicrobiota. Moreover, the present inventors have succeededin isolating intestinal bacteria that suppress intestinalcolonization and the like of oral bacteria and the like.