Toxic factors of Aeromonas hydrophila and Plesiomonas shigelloides.

In detail, exoproducts of Aeromonas hydrophila and Plesiomonas shigelloides were studied on the pathogenesis of diarrhoea. Enterotoxin, hemolysin and a cytotoxic factor were found in a fraction of culture filtrates of Aeromonas hydrophila with a molecular weight of approximatley 60,000. Apart there from a cytotoxic factor was also found in a fraction with molecular weight above 100,000. This fraction contained also endotoxin which was hemolytic, too. Enterotoxic activity was expressed by an accumulation of fluid in the ligated ileal loop and by increased vascular permeability in the skin of rabbit. Activation of adenylate cyclase was not found. Cytotoxic activity was represented by hemorrhagic reaction in the skin of rabbit, in some cases by sanguinous and mucous fluid in the ligated ileal loop and by significant morphological alterations on Vero cells leading to the death of cells. Culture filtrates of Plesiomonas shigelloides show only very low activity in biological experiments. Separation and purification steps led to a more concentrated and active material.