Fig. 1. BALB/c mice as a model for STSS.

(A and B) Virulence of human isolates in murine skin infection model. Cohorts of BALB/c mice (n = 5 per group) were infected with SN1 or NS33 strain via the skin route of infection. After day 3, 6, or 9 of challenge, the mice were culled and skin biopsy (A) and spleen (B) samples were harvested, processed, and plated to determine the bacterial burden. The results are shown as box and whisker plot, where the line in the box indicates the median, the box extremities indicate the upper and lower quartiles, and the whiskers show the minimum to maximum values. Statistical analysis was performed using nonparametric, unpaired Mann-Whitney U test to compare the two groups at each time point. **P < 0.01 and ***P < 0.001. (C and D) SDS–polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot profile of SpeC in serum samples collected at various time points after infection. Serum samples from SN1- or NS33-infected mice were collected on days 3, 6, and 9 after infection and run on 4 to 12% SDS-PAGE gels (C). Following protein transfer from the gel, the membrane was probed with rabbit anti-SpeC immunoglobulin G (IgG) primary antibody, followed by detection with sheep anti-rabbit IgG-AP (alkaline phosphatase), and developed using SIGMAFAST BCIP/NBT (bromochloroindolyl phosphate–nitro blue tetrazolium) substrate. rSpeC protein was also run as a positive control. Detection of SpeC is shown (D). MW, molecular weight. (E and F) SpeC detection in individual mouse serum samples from the day 6 collection. Serum samples from each individual mouse on day 6 following SN1/NS33 infection were also assessed for the presence of SpeC as described. A representative image of SDS-PAGE (E) and Western blot (F) is shown. The symbol “#” indicates the mice that had positive spleen culture.