[On the ecology of Plesiomonas shigelloides (author's transl)].

Studies on the generation time of P. shigelloides and its relation to incubation temperature have shown that this species in marked contrast to A. hydrophila does not multiply in temperature below 8 degrees C. These findings would explain the seasonal variations in the number of isolates from river-water observed in Japan. Colony counts of P. shigelloides organisms on IBG-agar from water of the river Main sampled during the month of August (water temperature 20 degrees C) have shown numbers of 10--100 c.f.u./ml. Thus P. shigelloides is present in surface water in Middle Europe. The presence of the germs could equally be demonstrated in the guts of many specimen of non-preying fish that had been caught during the months of July and August. When determining the bacterial species isolated from such material the possible presence of inositol-positive A. hydrophila strains has to be taken into account. Results of former studies on the suitability of Leifson-agar, Wilson-Blair- agar, SS-agar and IBG-agar then with pure cultures were confirmed by our work with faecal material from fish done this time. While favourable results were obtained on IBG- and SS-agar P. shigelloides could in no case be cultured on Leifson- and Wilson-Blair-agar.