Survival rates and bacterial loads in organs of intranasally immunized BALB/c mice after intranasal challenge with B. thailandensis (5 x 10⁶ CFU).

(A) Mice were immunized with PBS, SL3261 (vector), or SL3261/p1C3 (vaccine) via the intranasal route, then challenged. Mice were monitored for survival for a period up 150 h post-challenge. Results are represented in Kaplan-Meier survival curves and were analyzed by log-rank test. Log-rank: PBS vs. vaccine (P = 0.0031); vector vs. vaccine (P = 0.0128). Median survival: PBS, 64 h; SL3261, 84 h; and SL3261/p1C3, undefined). Results are representative of three independent experiments, five mice each. (B, C) Bacterial load in the organs of intranasally immunized mice 72 h post-challenge. All samples were plated for viable CFU on TSA and Ashdown’s agar. Each point represents a single mouse. ND indicates not detected. Data was analyzed by the Mann-Whitney U test. Nasal wash (P = 0.0012 vaccine vs. vector and P = 0.0025 vaccine vs. PBS); lung (P = 0.0043 vector vs. PBS); liver (P = 0.0043 vector vs. PBS).