Abstract
Direct fluorescent antibody technique (FAT) has been carried out for diagnosis of Edwardsiella tarda, Aeromonas hydrophila and atypical Aeromonas salmonicida infections. Fluorescent antibody (FA) was prepared against E. tarda EF-l, A. hydrophila CA-1 and atypical A. salmonicida C-5. To remove cross reactivity between A. hydrophila and atypical A. salmonicida, CA-1 FA and C-5 FA were absorbed with formalin-killed cells of atypical A. salmonicida and A. hydrophila, respec-tively. To determine if cross reaction occurred, the fish pathogen bacterial suspensions were heat fixed to slides and stained with the dilute FA preparations. At field survey, the heat-fixed smears of the kidney and the head ulcerative lesion from diseased eel were stained with FA preparations. In addition, these tissue samples were inoculated on 0.5% NaCl brain heart infusion agar 10% horse serum tryptosoy agar. EF-1 FA, CA-1 FA and C-5 FA reacted only to their respective antigens by dilution or absorption. From the 79 diseased eel, the respective numbers of eel where the bacteria were detected by the method were as follows: E. tarda, 60, 51; A. hydrophila, 15, 15 and A. salmonicida, 10, 7 (bacteria, by FAT, by culture). The FAT diagnosed 8 mixed infections as compared to 5 by culture, These results indicate that FAT was superior to culture method for diagnosis of the bacterial diseases in eel.
