FIG. 3.

CHO cells incubated for 3 h with representative strains of Y. enterocolitica: 937 (biotype 1A, invasive) (A), AM5 (biotype 1A, noninvasive) (B), and W22703c (biotype 2, invasive) (C). Large numbers of strain 937 are associated with groups of five or more CHO cells, whereas only a few bacteria (arrows) of strain AM5 are associated with these cells. Strain W22703c demonstrates a more even pattern of association with the CHO cells. Findings similar to those illustrated in panels A and B were observed with eight other strains of Y. enterocolitica biotype 1A, five invasive and three noninvasive. Giemsa stain was used. Bar = 5 μm.