EN
The interaction of Y. enterocolitica strains belonging to 4 and 1A biotypes with RAW264.7 murine macrophage- like cell monolayers was studied. Y. enterocolitica strains from humans and pigs were characterized in terms of their internalization and survival within RAW264.7 cell monolayers and their ability to escape from the cells. Y. enterocolitica biotype 4 strains invaded macrophage cell monolayers to a significantly higher degree than biotype 1A strains. However, biotype 1A strains exhibited a greater level of survival in macrophages than biotype 4 strains. All Y. enterocolitica strains tested demonstrated the ability to escape from macrophages. The mechanisms that allow Y. enterocolitica biotype 1A to survive within macrophages may contribute to the virulence of these organisms