The invention provides recombinant Streptococcus mutans strains that can be used to improve oral health. An embodiment of the invention provides a method of reducing the incidence or severity of dental caries in a dental caries-susceptible host comprising administering orally to the host an isolated recombinant S. mutans strain of the invention in an amount effective for replacement of dental caries-causing S. mutans host strains in the oral cavity of the host. The isolated recombinant S. mutans strain 10 can be contained in a mouthwash, toothpaste, chewing gum, floss, chewable tablet, food, or beverage.
