Abstract: A peptide having a sequence corresponding to a C-terminal portion of the Pseudomonas aeruginosa pilin protein is disclosed. The peptide is cross-reactive with surface peptides present in certain bacterial and fungal microorganisms, and is effective in inhibiting binding of such organisms to target epithelial cells. The peptide may also be employed in a vaccine composition, for producing immunity against such cross-reactive microorganisms. Also disclosed are methods of preparing peptides which are cross-reactive with the P. aeruginosa pilin peptide, and chimeric monoclonal antibodies immunoreactive with the pilin peptide.