[Detection of Yersinia ruckeri in rainbow trout in Czechoslovakia]

At the end of 1988 eight rainbow trouts Pd1 and nine rainbow trouts Pd2 were investigated at localities N and D with the increased mortality of rainbow trout. The pathological finding in dead and killed trout corresponded to the changes which are described in the so called ERM (enteric redmouth) salmonids. At the beginning of the year a similar case was found at locality B where 12 rainbow trouts Pd2 were examined. In the same period 15 trouts Pd2 at locality M were examined in which no large pathomorphological changes were observed. From the organs and intestines of locality N trout, from the intestines of locality D trout and the organs of locality B trout, in total 16 bacterial cultures were isolated, the morphological and biochemical characteristics of which correspond to the description of Y. ruckeri (Ross et al., Ewing et al., 1978). Fifteen sorbitol-nonfermenting strains came from the cases with clinical and pathomorphological findings while the only sorbitol-fermenting strain was isolated from a symptom-free carrier. These findings demonstrate that in the Czechoslovak conditions it is not possible to omit the difference in the virulence of sorbitol-fermenting and sorbitol-nonfermenting strains to rainbow trout.