Probiotics may compete for an ecological niche, or otherwise create conditions that are unfavorable to the pathogen taking hold of the intestinal tract rather than directly inhibiting the pathogen's growth or viability via immunomodulation. probiotics have the potential to alter the oral microbiota, and are further being researched to prevent or treat oral diseases such as dental caries and periodontal diseases that are associated with a shift in the biofilm's microbial composition and activity, and the resulting host reaction.