FIG 4.
MGAS2221 clearance from the lung requires NADPH oxidase but is independent of myeloperoxidase. (A to C) MGAS2221 was not cleared from the lungs of gp91phox−/− mice. C57BL/6J or gp91phox−/− mice were inoculated intratracheally and subcutaneously with 1.1 × 108 CFU and 5.9 × 107 CFU of MGAS2221, respectively, and euthanized at 24 h after inoculation. (A) Numbers of GAS CFU in the lung or at the skin infection sites of C57BL/6J and gp91phox−/− mice at 24 h after inoculation. (B and C) Representative images of Gram (B) and H&E (C) staining of lung sections of gp91phox−/− mice with pulmonary infection. The circle in panel B indicates one of many GAS clumps. The circle in panel C shows the lack of nuclear staining with hematoxylin of the location with the GAS clumps, and the arrow shows neutrophils with nuclear staining with hematoxylin in H&E stains. Figure 1C and D can be used as a comparison for panels C and B, respectively, for the effect of the gp91 knockout on the histopathology of MGAS2221 lung infection. (D) MGAS2221 clearance is independent of myeloperoxidase. C57BL/6J or MPO−/− mice were inoculated intratracheally with 8.7 × 106 CFU of MGAS2221. Presented are the numbers of GAS CFU in the lungs at 1 or 24 h after inoculation. Statistical analysis for P values was performed with the unpaired t test with Welch’s correction.