Effect of Heat on Viability of Mycobacteria leprae muris

Abstract

Clegg 1 developed a method of cultivating M. leprae, using media on which amebae were growing, later heating the cultures to 60°C. for 30 minutes. This procedure destroyed the amebae and symbiotic bacteria and resulted in what Clegg believed to be a pure culture of M. leprae. Other workers have stated that on exposing in vitro the bacilli of leprosy to 60° for 10 minutes the bacilli are killed. 2 It has been suggested, 3 presumably on the basis of the latter observations, that human leprosy might be susceptible to fever therapy. Denney 4 is attempting to determine if pyrotherapy is of any value in the disease and, if so, whether the effect is a direct thermal one. At his suggestion the following experiment was undertaken.

A leproma was removed from a rat, under sterile conditions, ground with sterile sand and suspended in physiologic (0.9%) saline solution. Seven equivalent amounts were placed in sterile test tubes and exposed to the following temperatures for five hours: 17°, 37°, 39°, 41°, 43°, 50° and 60°C. To serve as test subjects for each respective temperature, 7 groups of 10 rats each were selected of approximately the same weight (average of 200 gm. each) and age, except the first control group (17°C.) which were younger animals, averaging 80 gm. each. One-half cc. of the respective heat-treated saline-suspended M. leprae muris was injected subcutaneously into the right lower quadrant of the abdominal wall of each animal.