FIG 9.

Passive transfer of immune serum provides protective immunity against challenge with a lethal aerosol dose of WT B. pseudomallei K96243. Naive BALB/c mice were administered 1 ml of immune or naive serum intraperitoneally and challenged 48 h later with 7 LD₅₀ of WT B. pseudomallei strain K96243. BALB/c mice vaccinated with 10⁴ CFU of the B. mallei batA KO mutant and back-challenged with B. pseudomallei K96243 (30 days postvaccination) were used as an efficacy benchmark. Vaccination with the batA KO mutant and challenge with B. pseudomallei K96243 were both performed intratracheally using a Microsprayer device. (A) Kaplan-Meier survival curves. (B) Survival data during the acute and chronic phases of infection. (D, E, and F) Tissues were collected from mice that survived challenge (day 25), homogenized, diluted, and spread on agar plates to determine bacterial loads. The symbols show data for individual animals; the horizontal lines represent the mean total CFU for each group.