In vitro and in vivo experiments with Balb/c mice and Pseudomonas aeruginosa ATCC 27853 supported our hypothesis that bacterial lectins play an important role in the organotropy of infectious diseases. In vitro and in vivo adhesion of P. aeruginosa was mediated by N-acetylneuraminic acid (NANA) receptors. Blocking of the binding sites (lectins) on the bacterial surfaces with competitive specific carbohydrates (NANA) completely prevented the bacterial adhesion process in vitro. In vivo the number of adherent organisms in various organs decreased dramatically in the presence of NANA, whereas non-related carbohydrates (e.g. D-galactose) just showed negligible effects. Additionally, the application of NANA-treated organisms protected the animals from septicemia and death. Therefore, blocking of bacterial lectin receptors with specific carbohydrates might be of clinical relevance to prevent bacterial attachment to organ cells.