Fig. 9: Stevioside significantly protected mice from lethal Streptococcus pneumoniae infection.
From: Stevioside curbs Streptococcus pneumoniae infection via inhibiting capsule biosynthesis
A The survival rate of mice challenged with 5 × 108 S. pneumoniae D39 with indicated treatments. Mice were subcutaneously injected with 50 mg/kg stevioside in the 5% DMSO containing vehicle or an equal volume of vehicle (50 μl) immediately after infection (n = 9 mice each group), and administration was maintained three times daily. B Bacterial burden in the mouse lungs infected with S. pneumoniae D39. Mice infected with 1 × 108 S. pneumoniae D39 were treated as described above and sacrificed at 48 h postinfection. The lung tissues were removed and homogenized in PBS to determine the CFU by microbiological plating (n = 5 mice each group). C Gross observation and H&E staining of lung tissues from mice infected and treated as indicated. Scale bars, 100 µm and 50 µm. The levels of inflammatory cytokines IL-6 (D) and IL-1β (E) in the homogenates were determined by ELISA (n = 5 mice each group). F The survival rate of mice challenged by 5 × 108 S. pneumoniae D39 with indicated treatments (n = 9 mice each group). Mice were subcutaneously injected with 150 mg/kg stevioside in the 5% DMSO containing vehicle or an equal volume of vehicle (50 μl) immediately after infection, and the administration was maintained once daily for 3 days. The survival rates were analyzed using the log-rank (Mantel‒Cox) test (n = 9 mice each group), and the data presented as the means ± SD were analyzed using an unpaired two-tailed Student’s t-test. *P < 0.05, **P < 0.01 compared with the vehicle control group.
