Figure 5. In vivo assessment-direct injection of bacteria.

(a) Gross external (left) and internal (right) anatomical images of mice injected subcutaneously with 10⁸ CFU mL⁻¹ of S. pyogenes directly into the back (control) or into adhesive (2.5 wt% PDA crosslinked with 6.9 wt% PEI) after 3 days (n = 3). (b) Infection grade of primary tissue at injection site from mice injected with either bacteria only (control) or bacteria injected into adhesive. (c) Histological examination of the inflammatory response to S. pyogenes or adhesive injected with S. pyogenes. Cells stained with hematoxylin and eosin, (scale bar = 100 µm). Insets show 100x magnification of the designated region (scale bar = 5 µm). Inflammatory cells were identified based on cell morphology with →, ⇉, and ► (in yellow) corresponding to neutrophils, macrophages and lymphocytes, respectively.