The present invention relates to the use of a composition comprising a homotrimer, heterotrimer, homotetramer and/or heterotretramer of a component selected from the group comprising pentose, hexose, a L or D isomers thereof, a or form thereof, combinations thereof, an oxidised derivative thereof, or any mixtures thereof, as an agglutination agent for agglutinating enteric pathogens. The present invention also provides a method for selectively controlling and regulating the microbial ecosystem in the gastrointestinal tract of a subject in need thereof.