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Studies on Anthrax Immunity: 1. The Attenuation of Bacillus anthracis by Means of Sodium Chloride and Other Chemicals
S. J. Schilling
The Journal of Infectious Diseases
Vol. 38, No. 4 (Apr., 1926), pp. 341-353
Published by: Oxford University Press
Stable URL: http://www.jstor.org/stable/30083254
Page Count: 13
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It was found that sulphuric acid and copper sulphate hydrolyze agar when added to this medium, even in such dilute concentrations as would not be expected to inhibit growth of B. anthracis. The addition of 4.5% sodium chloride and the addition of 1% potassium ferrocyanide to standard agar appears to represent about the maximum concentration of these chemicals which may be used without completely inhibiting the growth of the anthrax bacillus. The growth-inhibiting concentration of sodium hydroxide is about 0.15%. An increased tolerance to sodium chloride, potassium ferrocyanide and sodium hydroxide could be noticed in successive transfers of the anthrax bacillus, as judged by the production of a more luxuriant growth. After growing the anthrax bacillus for 7 weeks on agar containing 1% potassium ferrocyanide, and for the same length of time on agar containing 0.15% sodium hydroxide and testing the culture by inoculating guinea-pigs, no decrease in virulence of the organism could be detected. After growing the anthrax bacillus for 6 weeks on agar containing 5% sodium chloride, marked attenuation of the anthrax bacillus was demonstrated by guinea-pig and rabbit inoculation. Attempts to immunize guinea-pigs with the NaCI attenuated culture failed. Presumably this was because sufficient intervals of time were not permitted to elapse between injections. It was found that rabbits could be successfully and safely immunized by the use of the cuture attenuated by growing on 5% sodium chloride agar, so that they withstood the injection of virulent cultures of the anthrax bacillus in quantities which are regularly fatal to normal animals.
The Journal of Infectious Diseases © 1926 Oxford University Press