FIG 6.

MGAS2221 ΔsagA induces robust neutrophil recruitment but is not significantly cleared at skin infection sites of C56BL/6J mice. (A) Representative H&E staining image of a whole ΔsagA mutant infection site 24 h after inoculation of 4.1 × 10⁷ CFU of MGAS2221 ΔsagA that was full of neutrophils with purple stain. The boxed area in panel A is shown in panel B at higher magnification to demonstrate the blue nuclear staining of neutrophils with hematoxylin. (C) Representative Gram stain image of the whole ΔsagA mutant infection site 24 h after inoculation that shows numerous dark-blue spots. The box in panel C is enlarged in panel D to show that the dark-blue spots were dark-blue GAS bacterial clumps. (E) Numbers of GAS bacteria at skin infection sites of C57BL/6J mice at 1 h and 24 h after inoculation of MGAS2221 (wt) and its ΔsagA, Δsse, and ΔspyCEP mutants. Scale bars: 200 μm (A and C) and 10 μm (B and D).