Figure 3

MRSA adhesion and infection of endothelial cells. Selected confocal image slices (0.5 μm thick) from one stack (from (A) the top of the cells through to (F) the bottom of the cells) were taken of HUVEC infected with MRSA under static conditions for 30 minutes. The brighter green dots are adherent MRSA UC18 cells. The arrows point to the same cell in each slice. In (A) only 2 MRSA can be seen at this location, whereas there is a cluster of 7 at the same location in the next slice (B). Two MRSA are seen at the same location in (C). Intracellular MRSA are more easily seen for this cell in (D). The inset in (F) shows a magnification of one cell and identification of bacteria (G). Since there is more than one adherent MRSA, this cell would be considered to be infected. If only this slice was used to analyze this particular endothelial cell, 16 MRSA would be used to determine the average number of MRSA per HUVEC. However, the entire stack was analyzed as cells may be bound in different planes along the height of the cell.