Figure 1

Internalization of S. aureus 6850 by A549 cells. A. Dose-response of internalization assay performed by adding increasing number of bacteria to constant number of cells. The internalization assay was performed as described in the experimental section. After 2 h, cells were detached with trypsin lyzed with dilute Triton X-100, and then internalized bacteria were assessed by count of colony forming units (cfu). B. Intracellular survival assay of S. aureus over a two-week interval. Note that at times after 6 hours, viable bacterial counts decreased, though viable bacteria were recovered from monolayers even 2 weeks after internalization. All values are mean ± standard deviation (SD) of at least three independent experiments. C. Viability tests were performed after 24 hours of internalization using bacterial m.o.i. of 100:1, or the presence of anti-CD95 (1 μg/ml) or etoposide (100 μM final concentration) as pro-apoptotic controls.