The long term objective of this proposed research is to determine the role of Aeromonas hydrophila virulence factors in the pathogenesis of disease in man. The virulence factors presently reported in the literature associated with A. hydrophila have not been clearly defined. A. hydrophila, a member of the family Vibrionaceae,is considered a significant human pathogen. This microorganism is responsible for causing a variety of diseases including acute bacterial diarrhea, septicemia, meningitis, endocarditis, corneal ulcers, peritonitis, and wound infections. These diseases have occurred in immunocompetent and immunocompromised individuals. A. hydrophila produce as well as possess a number of factors which may contribute to the overall virulence of the organism. We have discovered that A. hydrophila, isolate SSU, grown in Casamino acid-yeast extract (CYE) broth, can produce a number of interrelated toxins that play a role in some A. hydrophila mediated diseases. We have termed one of these toxins "cholera-toxin crossreactive (CTC) cytolysin" because of its ability to react with cholera antitoxin and cause fluid accumulation in rabbit intestinal loops as well as its destruction of Chinese hamster ovary cells and rabbit red blood cells. Our laboratory has purified CTC-cytolysin, a cytotoxic enterotoxin, to homogeneity and an amino acid sequence analysis revealed that the first 25 amino acids from the N-terminal end were identical to that of aerolysin reported by Howard and Buckley. In addition, we have purified to homogeneity a cytotonic enterotoxin and it was termed "non-CTC enterotoxin" because it does not react with cholera antitoxin and is free of cytolytic activity but is capable of causing fluid accumulation in rabbit intestinal loops. Our goals for the future will be to further characterize the antigenic, biological, and biochemical nature of these toxins; to determine the mechanism of action of the biological activities associated with CTC-cytolysin and non-CTC enterotoxin; to discover the type(s) of genetic information coding for the synthesis of Aeromonas CTC-cytolysin and non-CTC enteroxin. The proposed research involving CTC cytolysin and non-CTC enterotoxin as well as other virulence factors may aid in elucidating the means by which A. hydrophila cause human disease.