IN-VITRO INHIBITION OF EPITHELIAL-CELL INVASION BY AEROMONAS-HYDROPHILA AND VIBRIO SPECIES BY FISH AEROMONAS-HYDROPHILA MAJOR ADHESIN

A virulent strain of Aeromonas hydrophila (PPD 134/91) was obtained fr om the Primary Production Department, Singapore. Its major adhesin was isolated and purified by potassium thiocyanate extraction and Bio-Gel P-100 gel filtration. The ability of the protein in peak 1, termed ma jor adhesin, to inhibit bacteria from adhering to and invading host ce lls was studied in vitro using epithelioma papillosum cells of carp (E PC). Results showed that a concentration of 10 mu g ml(-1) of this maj or adhesin could competitively inhibit 28% of A. hydrophila PPD 134/91 from invading EPC cells in vitro. When the concentration was increase d to 40 mu g ml(-1), the major adhesin significantly cross-inhibited n ine other virulent or weakly virulent strains of A. hydrophila. In add ition, the major adhesin significantly inhibited not only another bact erial strain from the same family, Aeromonas sobria, but also strains of Vibrio spp. tested. Therefore, we suggest that the major adhesin of this virulent A. hydrophila strain has the potential to be used as a vaccine against the heterogeneous Aeromonas and Vibrio species.