FIG. 1.
Invasion of HeLa 229 cell monolayers by B. pertussis parental strains and mutants. Each B. pertussis strain (7 × 106 CFU) was added to a separate well of a 24-well tissue culture plate, each of which contained 7 × 104 epithelial cells. The invasion of HeLa 229 cells by B. pertussis was assayed as described in Materials and Methods. The values shown are means ± SEM in thousands of CFU recovered from gentamicin-treated monolayers in three to six experiments. The diamond symbol indicates P < 0.05 versus the parental B. pertussis strain, Tohama I (A) or 18323 (B).