Figure 4

C3 depletion by S. aureus in elevated glucose is associated with decreased complement-mediated killing of E. coli. (A) At elevated glucose levels, purified C3 is depleted from buffer in the presence S. aureus. Data are mean ± SE for 4 independent experiments. (B) In the absence of S. aureus, purified C3 is not depleted from buffer. Data are mean ± SE for 4 independent experiments. (C) S. aureus incubated with varying concentrations of NHS shows decreased residual C3 in the supernatant for 17 mmol/l glucose (black bars) compared with 3 mmol/l glucose (grey bars). Data are mean ± SE for 4 independent experiments. (D) For 2% NHS pre-incubated with S. aureus at 3 mmol/l glucose (grey bars) surviving E. coli decreased > 2 logs compared with 0% NHS. For 2% NHS pre-incubated with S. aureus at 17 mmol/l glucose (black bars) there was no difference in E. coli survival compared with 0% NHS. Data are mean ± SE for 4 independent experiments. (E) Control experiments performed without S. aureus in the preincubation step showed similar killing of E. coli at 3 mmol/l glucose (grey bars) or 17 mmol/l glucose (black bars). Data are mean ± SE for 3 independent experiments.