FIGURE 1.

SCV formation in phagocytic and non-phagocytic cells. S. aureus survives in higher numbers in non-phagocytic cells, such as osteoblasts and endothelial cells, than in phagocytic cells, such as macrophages. Because macrophages are professional phagocytes, they are able to eliminate intracellular bacteria very efficiently after 3 days, and no remaining bacteria are present to become SCVs. However, enhanced survival of S. aureus in osteoblasts and endothelial cells has been observed for up to 7 days. During the intracellular life stage of S. aureus, several bacterial cells switch to the SCV phenotype to resist intracellular stress conditions (unpublished data from L. Tuchscherr).