Pathological activities of Yersinia ruckeri, the enteric redmouth (ERM) bacterium.

The adherence and invasive capacities as well as the pathobiological activities exhibited by Yersinia ruckeri were examined. Although adhesive ability was dependent on the cell-line employed, all the strains showed moderate adhesion and invasiveness in the salmon cell-line CHSE-214. With regard to the extracellular products (ECP) all of them were strongly toxic for fish with LD50 ranging from 2 to 9.12 micrograms protein per g fish. In addition, all the ECP samples showed caseinase, gelatinase, amylase, lipase and phospholipase activities, hydrolysed esculin and displayed hemolytic activities for trout, salmon, sheep and human erythrocytes. Heat treatment (100 degrees C for 10 min) caused the loss of all these biological activities except the hydrolysis of gelatin. On the other hand, SDS-PAGE analysis of the LPS and protein components of the ECP revealed variations among strains depending on the serotype. The lack of lethal effects of the LPS present in the ECP was also demonstrated.