S. aureus has the ability to invade and persist within eukaryotic cells. It has been shown to be ingested by non-professional phagocytes. Reports have described that S. aureus possesses several cell surface adhesion molecules that facilitate its binding to non-professional phagocytes and also showed that Intracellular bacteria are capable of inducing apoptosis. The two global gene regulatory loci agr and sar have been demonstrated to play a role in the induction of apoptosis in epithelial cells by S. aureus RN6390 (wild type) since mutants in the agr or sar loci internalized, but did not induce cell death. The aim of the present study was to analyze the internalization and induction of apoptosis by S. aureus RN6390 and its
isogenic mutant agr-, RN6911, in MCF7 breast adenocarcinoma cells.The protocol for these experiments was based on the methods described by Bayles et al. (1998) Infect Immun. 66(1): 336-342. Our results have demonstrated that fibronectin is essential for efficient internalization of S. aureus RN6390 (wild type) within these cells. Six hours after internalization, breast adenocarcinoma cells showed morphological changes compatible with apoptosis. In contrast, mutant strain RN6911 (agr-) was internalized by the cultured cells at levels similar to those of RN6390 but failed to induce apoptosis. These results are in agreement with those reported for MAC-T cells and indicate that MCF7 cells can also be employed as a model system to study the effects on cellular death of mutants affecting virulence.
