TUBERCULOSIS INDUCED BY DROPLET NUCLEI INFECTION1

Abstract

The purpose of this study was to develop a standard procedure for inducing pulmonary tuberculosis of minimal intensity in 4 species of laboratory animals, a procedure suited to a study of nutrition as related to resistance to tuberculosis. Mice, rats, hamsters, and guinea pigs were caused to inhale virulent bovine or human tubercle bacilli as single cells in aerosol suspensions of fine droplet nuclei. Prom the results of earlier experiments it was assumed that the number of initial tubercles in the lungs of these animals might be predicted from bacilli per liter of aerosol, times liters of aerosol inhaled, as calculated from a formula for body weight. However, because of the varying degrees of activity of the several species during their stay in the infection chamber, the values for respiratory volumes, as given by Guyton's formula, were inadequate to account for the number of tubercles that developed in these animals. Hence, to allow for this activity, values for respiratory volume had to be increased. With these corrected values established, the number of initial tubercles that developed to macroscopic size in the lungs of the several species approximated the number of bacilli estimated to have been inhaled. It is concluded that under the conditions of these experiments the'initial response of mice, rats, hamsters, guinea pigs, and rabbits to inhaled infection by either human or bovine tubercle bacilli is predictable. Also, the number of initial tubercles that will develop to macroscopic size in the lungs of these animals, that is, the initial intensity of inhaled tuberculosis, can be predetermined.