Antagonism between Yersinia intermedia and Yersinia enterocolitica in water.

One strain of Yersinia enterocolitica and one strain of Y. intermedia were grown in peptone water at 25 or 37 degrees C, or in ground water at 15 degrees C. Similar growth rates were observed when these strains were cultivated separately in the same media and at the same temperature. Mixed cultures at 37 degrees C displayed equivalent growth rates. In contrast, mixed cultures incubated at 15 or 25 degrees C were regularly unfavourable to Y. enterocolitica, whereas they did not modify the growth of Y. intermedia. A bacteriophage active on Y. enterocolitica and not on Y. intermedia was characterized from the filtrate of mixed cultures at low temperatures. This phage produced by the lysogenic Y. intermedia strain might be a potential factor responsible for the inhibition of Y. enterocolitica, since no additional antibacterial factor or nutritional competition between Y. intermedia and Y. enterocolitica were found in the mixed cultures.