Immunofluorescent antibody staining revealed detectable levels of SpeB throughout MGAS5005Δ<i>srv</i> infected tissue as compared to MGAS5005 infected tissue.

<p>Subcutaneous abscesses from (A) MGAS5005 and (B) MGAS5005Δ<i>srv</i> infections were excised 1 dpi, sectioned, and stained with rabbit anti-SpeB sera and goat anti-GAS sera, and the appropriate fluorescent secondary antibody conjugate. (A, B) DIC/fluorescent images (4×) from an MGAS5005 infected animal (A) and an MGAS5005Δ<i>srv</i> infected animal (B) show the distribution of GAS (red) throughout the abscess. Randomly selected areas throughout the abscesses were examined for the colocalization of GAS and SpeB (20×, i–iv). MGAS5005 was readily detected (Ai–iv), but SpeB (green) was rarely detected in MGAS5005 infected samples (arrows, Aiii). In contrast, SpeB was detected in the presence of MGAS5005Δ<i>srv</i> throughout the infected samples (Bi–iv). Colocalized SpeB and GAS appear yellow. Representative images are shown. (C) Average total area of pixels (pixels²) was calculated for anti-GAS and anti-SpeB staining in the representative images shown of MGAS5005 and MGAS5005Δ<i>srv</i>. Comparable amounts of anti-GAS staining was observed, however, there is significantly more anti-SpeB staining in MGAS5005Δ<i>srv</i> images compared to MGAS5005 (* <i>p</i><0.01).