Figure 4. Stp1 is important for virulence of S. aureus.
(A) Ten, six week-old female C57BL/6J mice were intravenously injected with 2–5×107 CFU of S. aureus WT, Δstp1 or Δstk1 strains. As a control, ten mice were inoculated in parallel with PBS. Kaplan-Meier survival curves show the percent survival of mice after the infection. Note that 100% of mice infected with the WT and Δstk1 strains succumbed to infection, in contrast to only 10% of mice infected with the Δstp1 mutant. Survival of mice infected with the Δstp1 mutant was significantly different from that of the WT and the Δstk1 mutant (P value<0.0001, log rank test). However, mice infected with the Δstk1 mutant did not show a significant difference in survival compared to the WT (P value = 0.44, log rank test). (B) Kidneys harvested from the mice that were moribund or at the end of the experiment. Arrows represent abscesses that were observed on the infected kidneys. Note that a large number of abscesses are seen in the kidneys of mice infected with the Δstk1 mutant in comparison to those infected with the Δstp1 strain. One representative from ten infected kidney pairs after inoculation with the S. aureus strain is shown. (C) Histological examination of infected renal tissue was performed at 5 days post-infection. Kidneys were fixed in formalin, embedded in paraffin, thin-sectioned, stained with hematoxylin and eosin (H&E), and examined by microscopy as described previously [69], [97]. Abscesses and necrotic tissue are observed in kidneys of mice infected with WT and Δstk1 strains but not with the Δstp1 mutant.