Useful criteria for the identification of Bacillus anthracis and related species.

The methods suggested for the identification of species of the genus Bacillus in the invaluable monographs of Smith et al. (1946, 1952) have been applied to a collection of named cultures, and also have been utilized for the classification of approximately 400 strains of these organisms isolated from samples of blood, spinal fluid, surgical tissue, and other human and animal sources, as well as from laboratory dust, and soil. In the course of this work certain additional and modified techniques have been tested which appear to supplement those of Smith et al. in a useful way. In particular, the differential value of positive fat staining, of fermentation tests in tryptose agar, and of observations of the mode of spore germination has been appraised. Special procedures for differentiation of Bacillus licheniformis from Bacillus subtilis and Bacillus pumilus, and for the identification of both virulent and avirulent strains of Bacillus anthracis, have been tested. In the following report reference is made in detail only to the nine saprophytic species which in our experience are most likely to be encountered as contaminants from the laboratory dust, and in specimens from human beings or experimental animals, and which must be distinguished from B. anthracis. These species are B. cereus, B. mycoides (B. cereus var. mycoides, Smith et al., 1952), B. megaterium, B. subtilis, B. licheniformis, B. pumilus, B. circulans, B. brevis, and B. sphacericus.