Compositions which include a homotrimer, heterotrimer, homotetramer, and/or heterotetramer of a component such as pentose, hexose, an L or D isomer of a pentose or hexose, a &bgr；-form of a pentose or hexose, oxidized derivatives and mixtures of such compounds are disclosed as agglutination agents. The disclosed compositions are useful for agglutination of enteric pathogens and may be used for selectively controlling and regulating the microbial ecosystem in the gastrointestinal tract of a subject.
