In a pharmaceutical or dietetic preparation (A) for reducing and/or blocking the adhesion of pathogenic agents and organisms to eukaryotic cells (especially mammalian cells), containing carbohydrate(s) (I) having terminal uronic acid units, 10-100 (preferably 10-50) % of the terminal uronic acid units of (I) contain a double bond. An independent claim is included for the use of (I) (as described above) for reducing and/or blocking the adhesion of pathogenic agents and organisms to eukaryotic cells. - ACTIVITY : Antibacterial antifungal virucide antidote. - MECHANISM OF ACTION : Antiadhesive.