[Lysogeny among "Yersinia frederiksenii", "Y. kristensenii" and "Y. intermedia"].

We described the lysogeny among new species of Yersinia: Y. frederiksenii (47 strains), Y. kristensenii (57 strains) and Y. intermedia (133 strains). We found that 6.3% of the strains of Y. frederiksenii, 3.5% of Y. kristensenii and 2.2% of Y. intermedia were lysogenic for bacteriophages active on Y. enterocolitica (mainly the phenotypes incriminated in human pathology) and less frequently lysogenic for some strains of Y. frederiksenii, Y. kristensenii and Y. intermedia. One bacteriophage, isolated from the strain Y. frederiksenii 7291, should allow to discriminate between Y. enterocolitica phagovar IXa (susceptible) and IXb (resistant), and between the strains of Y. enterocolitica belonging to phagovar Xz and serovar 5 either biovar 1 (sometimes susceptible) or biovar 3 (always resistant).