Full text loading...
Chapter 13 : Response of Rabbits to Inhaled Tubercle Bacilli
The purpose of this chapter is to assemble in one place the characteristics of the disease produced in rabbits by the inhalation of virulent bovine and human types of tubercle bacilli and by the inhalation of BCG. Cavity formation with bronchial spread of the disease followed by death is produced in rabbits only by virulent bovine-type bacilli. Fully virulent bovine-type bacilli usually produced one grossly visible pulmonary tubercle for each inhaled unit of 1 to 3 bacilli that reached the alveolar spaces in both susceptible and resistant inbred Lurie rabbits. In Lurie’s resistant rabbits, virulent bovine-type tubercle bacilli did not multiply to as high a titer as they did in Lurie’s susceptible rabbits. The use of such aerosolized human-type bacilli enabled Lurie to develop his tubercle-count method, which is the most quantitative method for assaying innate and acquired resistance to tuberculosis in rabbits as well as the virulence of the infecting tubercle bacillus. Human-type tubercle bacilli are not fully virulent in rabbits. Most of the inhaled BCG bacilli are apparently destroyed by the alveolar macrophages before they can multiply appreciably. Without such multiplication, the degree of immunization would be negligible. Similar to rabbits, humans should be less immunized by the inhalation of BCG than by parenteral administration, in which higher doses of BCG can be injected and greater bacillary multiplication can occur (because the alveolar macrophages are bypassed).