This was one of the first examples of pathogenesis controlled by a two-component regulatory system and remains one of the best defined systems to study signal transduction associated with pathogenesis. Although there is no ideal animal model for B. pertussis , there are newly developed animal models for B. bronchiseptica, a close cousin of B. pertussis . Thus, the role of each virulence determinant and the role of coordinate gene regulation can now be evaluated. Note that the B. bronchiseptica model is not one of disease, but of colonization. Hemolytic on blood agar.
Bacteria colonize cilia of upper respiratory tract.
The first, colonization, has fever and coughing and lasts about 10 days. The first stage is usually thought to be a cold and is the highly infectious stage. It is here that the ciliated cells of the respiratory epithelium are destroyed. The second stage, toxemic, is characterized by the dry nonproductive cough, or paroxysmal cough. In the absence of ciliary activity, coughing becomes the only mechanism of clearing mucus, bacteria, and inflammatory debris from the respiratory tract.