In vivo virulence study of D39 and SK95 cps. A, Bacteremia at 6 and 24 hours, and survival of BALB/cJ mice that were intraperitoneally infected with either D39 or SK95 strains (4 mice per group). B, Bacteremia and survival of mice after intraperitoneal infection with acapsular pneumococcus (TIGR-JS, 4 mice/group), pneumococcus strain TIGR4-JS with D39 cps (FG34; 3 mice per group), and TIGR4-JS with SK95 cps (FG44; 3 mice per group). C, Bacteremia and survival of mouse after intraperitoneal infection with TIGR-JS with D39 cps (FG3) or with SK95 cps (FG4). Each group has 5 mice. Infection doses per mice were 103 colony-forming units (CFUs) of D39, 104 CFUs of SK95, or 105 CFUs of TIGR-JS, FG34, FG44, FG3, and FG4. B, C, For bacteremia, errors bars represent standard errors of the mean, and t test were used. Survival curves were compared using log-rank (Mantel-Cox) tests: P = .045 for D39 versus SK95 (A); P = .01 for both TIGR-JS versus FG34 and TIGR-JS versus FG44 (B); P = .02 for FG34 versus FG44 (C). h, hours.