FIG 7.

MGAS2221 Δsse skin infection sites are full of necrotic neutrophils that are associated with extensive GAS stains. C57BL/6J mice were subcutaneously inoculated with 5.4 × 10⁷ CFU MGAS2221 Δsse, and skin infection sites were collected at 24 h after inoculation and subjected to histological analyses. (A) Representative MPO IHC/hematoxylin staining image that shows that the Δsse mutant infection site was full of necrotic neutrophils. The brace indicates the layer of neutrophils with nuclear staining with hematoxylin at the edge of the infection site. The MPO staining intensities from the ImageJ analysis are presented in Fig. 5B. (B) Representative H&E staining image for the inside Δsse mutant infection site that shows the lack of nuclear staining with hematoxylin. (C) Representative Gram staining image that shows numerous GAS bacteria with dark-blue stain inside the infection site. The rest of the infection site that is not shown also had numerous stained GAS bacteria. Scale bars: 200 μm (A) and 10 μm (B and C).