Fig. 5

Macrophage viability was decreased after S. aureus infection in the presence of exogenous Fn. The viability of macrophages after infection (4 h) with strain 12,598 or SJC1221 in the presence of exogenous Fn was determined by (a) the MTT assay, or visualized either by (b) crystal violet staining or (c) PI staining. Damaged cells were observed by detecting fluorescent PI (red) under a fluorescence microscope with the magnification of 100×. Cell viability was defined as 100% when cells were cultured in medium only (untreated). * P < 0.05