Figure 12. Macrophages recovered from S. aureus biofilm infections harbor viable intracellular bacteria.

Viable macrophages (F4/80⁺, 7-AAD⁻) were recovered from tissues surrounding biofilm infections at day 7 post-infection by FACS, whereupon gentamicin protection assays were performed to evaluate the presence of viable intracellular bacteria. Controls included sorted macrophages without any antibiotic treatment (to assess extra- and intracellular bacteria) and macrophages treated with rifampicin, which is capable of penetrating the eukaryotic cell membrane. Results are expressed as the number of viable S. aureus (CFU per 10³ biofilm-associated macrophages) and represent the mean ± SEM of five independent experiments.