Figure 3. Staphylococcus aureus lacking SpA does not inhibit osteoblast proliferation.
(A) Live or formaldehyde fixed S. aureus Newman was lysed in RIPA buffer containing 1 X protease inhibitor cocktail on ice for 10 minutes and probed with anti-protein A IgY antibodies. Protein bands were detected using species specific horseradish peroxidase-conjugated secondary antibody and chemiluminescence. (B) Osteoblasts (5×105 cells/ml) were preincubated with either control buffer or formaldehyde fixed S. aureus Newman, Newman SpA deficient or Newman pCU1spa (1×109 cells/ml) or purified protein A (50 µg/ml) for a total period of 21 days. After days 7, 14 and 21 osteoblasts were removed by trypsinization and proliferation was determined by counting cells on a haemocytometer. *P<0.01, **P = NS, n = 5.