Sodium chloride-enhanced adherence of Edwardsiella tarda to HEp-2 cells

The adherence of Edwardsiella tarda strains to HEp-2 cells was studied by the viable cell count and direct microscopic count methods. Three selected E. tarda strains having different hemagglutination activities against guinea pig erythrocytes were cultured in a peptone-yeast extract broth supplemented with 3% NaCl (3%-NaCl culture) or without NaCl (0%-NaCl culture). Strain FK1051 showed significantly higher adherence in the 3%-NaCl culture than in the 0%-NaCl culture. A similar adherence pattern was observed in strain KG8401, though the adherence of the 0%-NaCl culture was higher than that of FK1051. In contrast, both cultures of strain SU166 were low in the adherence. These adherence patterns to the HEp-2 cells correlated well with the previously reported hemagglutinating activities of the strains. N-acetylneuraminic acid markedly inhibited the adherence as well as the hemagglutination. This NaCl-enhanced adherence may be involved in pathogenesis of E. tarda infection particularly in marine fish.