USING A NEW INBRED FISH MODEL AND CULTURED FISH TISSUE-CELLS TO STUDYAEROMONAS-HYDROPHILA AND YERSINIA-RUCKERI PATHOGENESIS

An inbred strain of the southern platyfish, Xiphophorus maculatus, was used as a host for Aeromonas hydrophila and Yersinia ruckeri infectio ns. The infections were initiated by holding the platyfish in inoculat ion baths containing dilutions of virulent A. hydrophila or Y. ruckeri strains. Inoculating the platyfish in this manner resulted in a dose- dependent mortality over a range of bacterial input from 10(5) to 10(8 ) A. hydrophila and 10(6) to 10(8) Y. ruckeri/ml. Clinical manifestati ons of A. hydrophila infections were noted in infected platyfish that eventually died, but not in platyfish that survived. In this model, th e Y. ruckeri infected fish died before obvious signs of infection were detected. The A. hydrophila strain used to establish the infections w as recovered from the kidney and intestine of infected fish that died, but not from survivors receiving the same inoculation dose. Both infe ctive bacteria were tested for the ability to invade a number of diffe rent fish and human cultured cells. A. hydrophila strain TF7 did not i nvade any of the cells tested, whereas the Y. ruckeri strain invaded f ish derived cultured cells, but not human derived Hep-2 cells. (C) 199 6 Academic Press Limited