Figure 6.
Capsule-free RS218 is avirulent in mice. Kaplan-Meier survival curves of mice per dose of different strains. (A) K1-capsulated RS218 (Cap+) in leukopenic mice; (B) capsule-free RS218 (Cap−) in leukopenic mice; (C) Cap+ and Cap− RS218 in immune competent mice. The median lethal dose is 103–104 CFU for Cap+ and 106–107 CFU for Cap- RS218 in leukopenic mice, a difference of 3 orders of magnitude. The median lethal dose in normal mice is 106–107 CFU for Cap+ RS218, while Cap− RS218 is not lethal at doses as high as 109 CFU. Mouse survival was monitored for 5 days and the cumulative probability of survival was plotted for each dose. The mouse number n of each treatment is labeled by each curve. Log rank test: p values are listed for lower doses compared to the highest dose of each strain.