Aerosol infection of mice with Bordetella pertussis

Abstract

Aerosol inhalation of B. pertussis Tohama phase I resulted in a reproducible and uniform infection of mice (strain DDY or ICR). Mice in groups of 10 exposed for 30 min to aerosols generated from bacterial suspensions of 109 and 1010 organisms/ml resulted in mean bacterial counts of 2.3 (.+-. 0.3) .times. 104 and 1.0 (.+-. 0.3) .times. 105 colony-forming units [CFU], respectively, in the lung of each animal. Subsequent studies using a 30 min aerosol inoculation of ICR mice with 2 .times. 109 bacterial cells/ml showed that B. pertussis cells reached a maximum of .apprx. 107 CFU/lung 14 days after inhalation. Deaths (10-100%, depending on mouse age) occurred 10-14 days after exposure. Lung wt and leukocyte count increased from basal values of 100 mg and 104 leukocytes/mm3 to a plateau of 950 mg and 1.95 .times. 105 leukocytes/mm3, respectively, 14 days after challenge. There was a significantly reduced rate of body wt gain by infected mice compared to non-infected mice. With mortality as the criterion for disease, susceptibility varied with the age of mice as follows: 10 days old > 18 > 28 > 49. Bacteria were associated with ciliated respiratory epithelial cells by scanning electron microscopy.