FIG. 7.
Ability of the O-antigen-deficient strain of B. parapertussis to colonize B. pertussis-immune hosts. C57BL/6 mice were inoculated with 5 × 105 CFU of B. pertussis (Bp) or B. parapertussis (Bpp). Immunized and naive mice were challenged 28 days later with 5 × 105 CFU of B. parapertussis (white bars) or the O-antigen-deficient strain of B. parapertussis (BppΔO-ag; hatched bars). Mice were sacrificed 3 days after secondary inoculation for the quantification of bacterial numbers in the nasal cavities (A), tracheae (B), and lungs (C). All values are expressed as log10 means ± standard deviations. *, P < 0.05; **, P < 0.01.