Resistance of Bordetella pertussis phase I to mucociliary clearance by rabbit tracheal mucous membrane.

Cultivated mucous membrane of rabbit trachea was point inoculated with Bordetella pertussis phase I or III. Phase I (virulent) bacteria were found to be infective at the point-inoculated site, but phase III (avirulent) bacteria rarely showed such behavior. After inoculation, homogenized segments of mucous membrane were spread on plates. Large numbers of phase I bacteria were recovered from the inoculated segment; however, the laryngeal segment was the site of recovery of large numbers of phase III bacteria. The difference was not due to the ciliostatic bacterial toxin. After coinoculation with phase I and III bacteria, phase III bacteria were recognized at the laryngeal end, whereas phase I bacteria were recognized at the inoculated site. Therefore, the adherence of the bacteria to the ciliated epithelium is considered to be the most probable mechanism of the resistance to the mucociliary stream. Scanning electron microscopy facilitated visualization of phase I bacteria adhering to the inoculated site.