Survival rate and immune response in K. pneumoniae-inoculated mice.

A and B, Eight mice per group were infected with the wild-type and the wbbO mutant strains at an intraperitoneal (IP) dose of 1×103 CFU/animal or an intragastrical (IG) dose of 1×106 CFU/animal. Survival of mice was monitored for 4 (IP) or 6 (IG) weeks. ▪, NTUH-K2044; □, K2044 wbbO; ▴, NTUH-A4528; ▵, A4528 wbbO mutant (K2044 wbbO vs. parent, P = 0.0002 (IP) and P = 0.4417 (IG); A4528 wbbO vs. parent, P<0.0001 (IP) and P = 0.0129 (IG); log-rank test). C to F, Equivalent doses (1×103 CFU) of the wild-type, the wbbO mutant, and the wbbO mutant with the wb cluster complementation were inoculated into mice (4 mice per group) by IP injection. Surviving animals were sacrificed at 24 hours after challenge. Bacterial loads were measured in the blood (C), liver, and spleen (D); TNF-α (E) and IL-6 (F) levels were measured in the serum. Log10 CFU was standardized per 0.1 gram wet organ weight. IL-6 and TNF-alpha levels were measured by ELISA. Data are presented as means ± standard deviations. ND, not detected. **P<0.01 and *P<0.05 by Student's t test (wbbO mutant group vs. wild-type group or the wbbO mutant with the wb cluster complementation group).