TWENTY-SECOND ANNUAL EASTERN FISH HEALTH WORKSHOP ROYAL PAVILLION RESORT, ATLANTIC BEACH, NC MARCH 18 - 20, 1997 Detection of Aeromonas salmonicida by Culture and Serodiagnostic Assays following Stress Induced Furunculosis Tests Graham L. Bullock1 and Rocco C. Cipriano2 1The Conservation Fund, Freshwater Institute, P.O. Box 1746, Shepherdstown, WV, 25443; 2USGS, Biological Resources Division, National Fish Health Research Laboratory, 1700 Leetown Road, Kearneysville, WV, 25430 Stress induced furunculosis (SIF) tests had previously enhanced detection of Aeromonas salmonicida in covertly infected rainbow trout. Examination of mucus, gills, heart, liver, spleen, kidney, and intestine by direct culture of these tissues on CBB agar (Tryptic Soy agar with 0.01% Coomassie brilliant blue) indicated mucus and gills were the best sources of isolation from the stressed trout. We report herein on detection of A. salmonicida from stressed trout using direct culture and commercial ELISA and direct fluorescent antibody (dFAT) tests. Eighty trout were injected with 20 mg/kg prednisolone acetate, stocked into tanks containing 12.5oC tank water, and water temperature raised to 20oC over 6 h. Mucus, gill, kidney and spleen samples were taken from 20 trout after 3, 4, 5, and 6 d exposure to heated water. Similar tissues were taken from 20 non-injected, non-stressed control trout. Tissues were diluted 1:1 in phosphate buffer and cultured on CBB agar or tested by ELISA and dFAT. Antibody conjugates were obtained from DiagXotics Inc. (Wilton CT) and used as instructed. Tissues from control trout were not positive for A. salmonicida by any procedure. In SIF-tested trout, culture was most sensitive with 59 of the 320 tissues (10.4%) positive. Direct fluorescence detected 9 samples (2.0%) while ELISA detected 6 (1.9%). Mucus was optimal source for detecting A. salmonicida by culture with 30 of 80 (37.5%) positive followed by kidney, 15 of 80 (18.7%); gills, 10 of 80 (12.5%); and spleen, 4 of 80 (5.0%). Additional tests were run with the ELISA and dFAT reagents on 10 A. salmonicida and 20 motile aeromonad cultures. All A. salmonicida cultures reacted with ELISA and direct fluorescence with the lowest level of detection at 104 cells. One motile aeromonad isolate reacted by ELISA and dFAT procedures. Return to 22nd Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page